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  • Life and Medical Sciences  (1.436)
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  • Aircraft Propulsion and Power
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  • 1
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    High Temperature Investigations into an Active Turbine Blade Tip Clearance Control Concept (2008)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-06-06
    Beschreibung: System studies have shown the benefits of reducing blade tip clearances in modern turbine engines. Minimizing blade tip clearances throughout the engine will contribute materially to meeting NASA s Ultra-Efficient Engine Technology (UEET) turbine engine project goals. NASA GRC is examining two candidate approaches including rub-avoidance and regeneration which are explained in subsequent slides.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 2007 NASA Seal/Secondary Air System Workshop; 101-123; NASA/CP-2008-215263/VOL1
    Format: text
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  • 2
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    A Theoretical Solid Oxide Fuel Cell Model for Systems Controls and Stability Design (2008)
    In:  Other Sources
    Details
    Publikationsdatum: 2018-06-06
    Beschreibung: As the aviation industry moves toward higher efficiency electrical power generation, all electric aircraft, or zero emissions and more quiet aircraft, fuel cells are sought as the technology that can deliver on these high expectations. The hybrid solid oxide fuel cell system combines the fuel cell with a micro-turbine to obtain up to 70% cycle efficiency, and then distributes the electrical power to the loads via a power distribution system. The challenge is to understand the dynamics of this complex multidiscipline system and the design distributed controls that take the system through its operating conditions in a stable and safe manner while maintaining the system performance. This particular system is a power generation and a distribution system, and the fuel cell and micro-turbine model fidelity should be compatible with the dynamics of the power distribution system in order to allow proper stability and distributed controls design. The novelty in this paper is that, first, the case is made why a high fidelity fuel cell mode is needed for systems control and stability designs. Second, a novel modeling approach is proposed for the fuel cell that will allow the fuel cell and the power system to be integrated and designed for stability, distributed controls, and other interface specifications. This investigation shows that for the fuel cell, the voltage characteristic should be modeled but in addition, conservation equation dynamics, ion diffusion, charge transfer kinetics, and the electron flow inherent impedance should also be included.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Journal of Fuel Cell Science and Technology; Volume 5
    Format: text
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  • 3
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    NASA C-17 Usage Overview (2008)
    In:  CASI
    Details
    Publikationsdatum: 2018-06-06
    Beschreibung: The usage and integrated vehicle health management of the NASA C-17. Propulsion health management flight objectives for the aircraft include mapping of the High Pressure Compressor in order to calibrate a Pratt and Whitney engine model and the fusion of data collected from existing sensors and signals to develop models, analysis methods and information fusion algorithms. An additional health manage flight objective is to demonstrate that the Commercial Modular Aero-Propulsion Systems Simulation engine model can successfully execute in real time onboard the C-17 T-1 aircraft using engine and aircraft flight data as inputs. Future work will address aircraft durability and aging, airframe health management, and propulsion health management research in the areas of gas path and engine vibration.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
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  • 4
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    Ceramic matrix composite turbine engine vane (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A vane has an airfoil shell and a spar within the shell. The vane has an outboard shroud at an outboard end of the shell and an inboard platform at an inboard end of the shell. The spar has a first chamber essentially along the suction side and a second chamber along the pressure side opposite the first chamber.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
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  • 5
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    Seal Technology Development for Advanced Component for Airbreathing Engines (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Key aspects of the design of sealing systems for On Rotor Combustion/Wave Rotor (ORC/WR) systems were addressed. ORC/WR systems generally fit within a broad class of pressure gain Constant Volume Combustors (CVCs) or Pulse Detonation Combustors (PDCs) which are currently being considered for use in many classes of turbine engines for dramatic efficiency improvement. Technology readiness level of this ORC/WR approaches are presently at 2.0. The results of detailed modeling of an ORC/WR system as applied to a regional jet engine application were shown to capture a high degree of pressure gain capabilities. The results of engine cycle analysis indicated the level of specific fuel consumption (SFC) benefits to be 17 percent. The potential losses in pressure gain due to leakage were found to be closely coupled to the wave processes at the rotor endpoints of the ORC/WR system. Extensive investigation into the sealing approaches is reported. Sensitivity studies show that SFC gains of 10 percent remain available even when pressure gain levels are highly penalized. This indicates ORC/WR systems to have a high degree of tolerance to rotor leakage effects but also emphasizes their importance. An engine demonstration of an ORC/WR system is seen as key to progressing the TRL of this technology. An industrial engine was judged to be a highly advantageous platform for demonstration of a first generation ORC/WR system. Prior to such a demonstration, the existing NASA pressure exchanger wave rotor rig was identified as an opportunity to apply both expanded analytical modeling capabilities developed within this program and to identify and fix identified leakage issues existing within this rig. Extensive leakage analysis of the rig was performed and a detailed design of additional sealing strategies for this rig was generated.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215479 , E-16656
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  • 6
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    Analysis of Plume Effects on Sonic Boom Signature for Isolated Nozzle Configurations (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Computational fluid dynamics (CFD) analysis has been performed to study the plume effects on sonic boom signature for isolated nozzle configurations. The objectives of these analyses were to provide comparison to past work using modern CFD analysis tools, to investigate the differences of high aspect ratio nozzles to circular (axisymmetric) nozzles, and to report the effects of underexpanded nozzle operation on boom signature. CFD analysis was used to address the plume effects on sonic boom signature from a baseline exhaust nozzle. Near-field pressure signatures were collected for nozzle pressure ratios (NPRs) between 6 and 10. A computer code was used to extrapolate these signatures to a ground-observed sonic boom N-wave. Trends show that there is a reduction in sonic boom N-wave signature as NPR is increased from 6 to 10. The performance curve for this supersonic nozzle is flat, so there is not a significant loss in thrust coefficient as the NPR is increased. As a result, this benefit could be realized without significant loss of performance. Analyses were also collected for a high aspect ratio nozzle based on the baseline design for comparison. Pressure signatures were collected for nozzle pressure ratios from 8 to 12. Signatures were nearly twice as strong for the two-dimensional case, and trends also show a reduction in sonic boom signature as NPR is increased from 8 to 12. As low boom designs are developed and improved, there will be a need for understanding the interaction between the aircraft boat tail shocks and the exhaust nozzle plume. These CFD analyses will provide a baseline study for future analysis efforts.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215414 , AIAA Paper 2008-3729 , E-16535-1
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  • 7
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    Signal Detection Theory Applied to Helicopter Transmission Diagnostic Thresholds (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Helicopter Health Usage Monitoring Systems (HUMS) have potential for providing data to support increasing the service life of a dynamic mechanical component in the transmission of a helicopter. Data collected can demonstrate the HUMS condition indicator responds to a specific component fault with appropriate alert limits and minimal false alarms. Defining thresholds for specific faults requires a tradeoff between the sensitivity of the condition indicator (CI) limit to indicate damage and the number of false alarms. A method using Receiver Operating Characteristic (ROC) curves to assess CI performance was demonstrated using CI data collected from accelerometers installed on several UH60 Black Hawk and AH64 Apache helicopters and an AH64 helicopter component test stand. Results of the analysis indicate ROC curves can be used to reliably assess the performance of commercial HUMS condition indicators to detect damaged gears and bearings in a helicopter transmission.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215262 , E-16530
    Format: application/pdf
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  • 8
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    An Investigation of Noise Reduction for the 3BB Nozzle with a Pylon Using External Flaps (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: Flaps (or half wedges) attached to the sides of a pylon are shown to result in a small but clear noise benefit. Noise radiated towards the ground is reduced apparently through a deflection and thickening of the fan stream underneath. Based on results from the current as well as concurrent investigations at the University of California at Irvine, it is recommended that further tests in a larger facility simulating realistic engine conditions be considered.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215288 , E-16562
    Format: application/pdf
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  • 9
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    Intelligent Engine Systems: Thermal Management and Advanced Cooling (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The objective is to provide turbine-cooling technologies to meet Propulsion 21 goals related to engine fuel burn, emissions, safety, and reliability. Specifically, the GE Aviation (GEA) Advanced Turbine Cooling and Thermal Management program seeks to develop advanced cooling and flow distribution methods for HP turbines, while achieving a substantial reduction in total cooling flow and assuring acceptable turbine component safety and reliability. Enhanced cooling techniques, such as fluidic devices, controlled-vortex cooling, and directed impingement jets, offer the opportunity to incorporate both active and passive schemes. Coolant heat transfer enhancement also can be achieved from advanced designs that incorporate multi-disciplinary optimization of external film and internal cooling passage geometry.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215236 , E-16495
    Format: application/pdf
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  • 10
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    Intelligent Engine Systems: Thermal Management and Advanced Cooling (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The objective of the Advanced Turbine Cooling and Thermal Management program is to develop intelligent control and distribution methods for turbine cooling, while achieving a reduction in total cooling flow and assuring acceptable turbine component safety and reliability. The program also will develop embedded sensor technologies and cooling system models for real-time engine diagnostics and health management. Both active and passive control strategies will be investigated that include the capability of intelligent modulation of flow quantities, pressures, and temperatures both within the supply system and at the turbine component level. Thermal management system concepts were studied, with a goal of reducing HPT blade cooling air supply temperature. An assessment will be made of the use of this air by the active clearance control system as well. Turbine component cooling designs incorporating advanced, high-effectiveness cooling features, will be evaluated. Turbine cooling flow control concepts will be studied at the cooling system level and the component level. Specific cooling features or sub-elements of an advanced HPT blade cooling design will be downselected for core fabrication and casting demonstrations.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215238 , E-16497
    Format: application/pdf
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  • 11
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    System Study: Technology Assessment and Prioritizing Update (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: For the Intelligent Engine System (Propulsion 21) study, each technology was evaluated to determine the impact to fuel burn, acoustics, and NOx emissions. The optimum combination of technologies and their overall benefits to the system were also evaluated, resulting in noise improvement potential of 1.89 EPNdB cumulative margin,-1.34 percent fuel burn, and 50 percent NOx reduction from the 2015 UEET-QAT baseline. All the technology evaluations, except T18-20D, were based on newengines, where the engine was resized to obtain the maximum system benefit while maintaining the same cycle parameters as the 2015 UEET-QAT baseline. The impact of turbine clearance control on deteriorated engines, T18-20D, was also evaluated. Recommendations for future system study work include, but were not limited to, validation of a university-developed engine deterioration model and customer value analysis as figures of merit beside fuel burn, emissions, and acoustics.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215224 , E-16492
    Format: application/pdf
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  • 12
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    An Adaptive Instability Suppression Controls Method for Aircraft Gas Turbine Engine Combustors (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: An adaptive controls method for instability suppression in gas turbine engine combustors has been developed and successfully tested with a realistic aircraft engine combustor rig. This testing was part of a program that demonstrated, for the first time, successful active combustor instability control in an aircraft gas turbine engine-like environment. The controls method is called Adaptive Sliding Phasor Averaged Control. Testing of the control method has been conducted in an experimental rig with different configurations designed to simulate combustors with instabilities of about 530 and 315 Hz. Results demonstrate the effectiveness of this method in suppressing combustor instabilities. In addition, a dramatic improvement in suppression of the instability was achieved by focusing control on the second harmonic of the instability. This is believed to be due to a phenomena discovered and reported earlier, the so called Intra-Harmonic Coupling. These results may have implications for future research in combustor instability control.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215202 , E-16414-1
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  • 13
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    Low-noise fan exit guide vanes (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-08-28
    Beschreibung: Low-noise fan exit guide vanes are disclosed. According to the present invention a fan exit guide vane has an outer shell substantially shaped as an airfoil and defining an interior cavity. A porous portion of the outer shell allows communication between the fluctuations in the air passing over the guide vane and the interior cavity. At least one acoustically resonant chamber is located within the interior cavity. The resonant chamber is in communication with the porous portion of the outer perimeter. The resonant chamber is configured to reduce the noise generated at a predetermined frequency. In various preferred embodiments, there is a plurality of acoustically resonant chambers located within the interior cavity. The resonant chambers can be separated by one or more partitions within the interior cavity. In these embodiments, the resonant chambers can be configured to reduce the noise generated over a range of predetermined frequencies.
    Schlagwort(e): Aircraft Propulsion and Power
    Format: application/pdf
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  • 14
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    Comparison Between Numerically Simulated and Experimentally Measured Flowfield Quantities Behind a Pulsejet (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Pulsed combustion is receiving renewed interest as a potential route to higher performance in air breathing propulsion systems. Pulsejets offer a simple experimental device with which to study unsteady combustion phenomena and validate simulations. Previous computational fluid dynamic (CFD) simulation work focused primarily on the pulsejet combustion and exhaust processes. This paper describes a new inlet sub-model which simulates the fluidic and mechanical operation of a valved pulsejet head. The governing equations for this sub-model are described. Sub-model validation is provided through comparisons of simulated and experimentally measured reed valve motion, and time averaged inlet mass flow rate. The updated pulsejet simulation, with the inlet sub-model implemented, is validated through comparison with experimentally measured combustion chamber pressure, inlet mass flow rate, operational frequency, and thrust. Additionally, the simulated pulsejet exhaust flowfield, which is dominated by a starting vortex ring, is compared with particle imaging velocimetry (PIV) measurements on the bases of velocity, vorticity, and vortex location. The results show good agreement between simulated and experimental data. The inlet sub-model is shown to be critical for the successful modeling of pulsejet operation. This sub-model correctly predicts both the inlet mass flow rate and its phase relationship with the combustion chamber pressure. As a result, the predicted pulsejet thrust agrees very well with experimental data.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215432 , AIAA-2008-5046 , E-16597 , 44th Joint Propulsion Conference and Exhibit; Jul 21, 2008 - Jul 23, 2008; Hartford, CT; United States
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  • 15
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    Data Turbine Activities at NASA (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Mission Support Features: a) Shirtsleeve environment, . 18 scientists; b) worldwide deployment experience; c) Extensive modifications to support in-situ and remote sensing instruments 1) zenith and nadir viewports; 2) modified power systems; 3) 19 inch rack mounting; 4) on-board data acquisition network.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 1st Workshop of the Open Source Data Turbine Initiative; Oct 07, 2008; La Jolla, CA; United States
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  • 16
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    Model-Based Fault Tolerant Control (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The Model Based Fault Tolerant Control (MBFTC) task was conducted under the NASA Aviation Safety and Security Program. The goal of MBFTC is to develop and demonstrate real-time strategies to diagnose and accommodate anomalous aircraft engine events such as sensor faults, actuator faults, or turbine gas-path component damage that can lead to in-flight shutdowns, aborted take offs, asymmetric thrust/loss of thrust control, or engine surge/stall events. A suite of model-based fault detection algorithms were developed and evaluated. Based on the performance and maturity of the developed algorithms two approaches were selected for further analysis: (i) multiple-hypothesis testing, and (ii) neural networks; both used residuals from an Extended Kalman Filter to detect the occurrence of the selected faults. A simple fusion algorithm was implemented to combine the results from each algorithm to obtain an overall estimate of the identified fault type and magnitude. The identification of the fault type and magnitude enabled the use of an online fault accommodation strategy to correct for the adverse impact of these faults on engine operability thereby enabling continued engine operation in the presence of these faults. The performance of the fault detection and accommodation algorithm was extensively tested in a simulation environment.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215273 , E-16555
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  • 17
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    Assessment of Current Jet Noise Prediction Capabilities (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: An assessment was made of the capability of jet noise prediction codes over a broad range of jet flows, with the objective of quantifying current capabilities and identifying areas requiring future research investment. Three separate codes in NASA s possession, representative of two classes of jet noise prediction codes, were evaluated, one empirical and two statistical. The empirical code is the Stone Jet Noise Module (ST2JET) contained within the ANOPP aircraft noise prediction code. It is well documented, and represents the state of the art in semi-empirical acoustic prediction codes where virtual sources are attributed to various aspects of noise generation in each jet. These sources, in combination, predict the spectral directivity of a jet plume. A total of 258 jet noise cases were examined on the ST2JET code, each run requiring only fractions of a second to complete. Two statistical jet noise prediction codes were also evaluated, JeNo v1, and Jet3D. Fewer cases were run for the statistical prediction methods because they require substantially more resources, typically a Reynolds-Averaged Navier-Stokes solution of the jet, volume integration of the source statistical models over the entire plume, and a numerical solution of the governing propagation equation within the jet. In the evaluation process, substantial justification of experimental datasets used in the evaluations was made. In the end, none of the current codes can predict jet noise within experimental uncertainty. The empirical code came within 2dB on a 1/3 octave spectral basis for a wide range of flows. The statistical code Jet3D was within experimental uncertainty at broadside angles for hot supersonic jets, but errors in peak frequency and amplitude put it out of experimental uncertainty at cooler, lower speed conditions. Jet3D did not predict changes in directivity in the downstream angles. The statistical code JeNo,v1 was within experimental uncertainty predicting noise from cold subsonic jets at all angles, but did not predict changes with heating of the jet and did not account for directivity changes at supersonic conditions. Shortcomings addressed here give direction for future work relevant to the statistical-based prediction methods. A full report will be released as a chapter in a NASA publication assessing the state of the art in aircraft noise prediction.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215275 , AIAA Paper 2008-2933 , E-16545 , 14th Aeroacoustics Conference; May 05, 2008 - May 07, 2008; Vancouver; Canada
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  • 18
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    A Numerical Study of Anti-Vortex Film Cooling Designs at High Blowing Ratio (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A concept for mitigating the adverse effects of jet vorticity and liftoff at high blowing ratios for turbine film cooling flows has been developed and studied at NASA Glenn Research Center. This "anti-vortex" film cooling concept proposes the addition of two branched holes from each primary hole in order to produce a vorticity counter to the detrimental kidney vortices from the main jet. These vortices typically entrain hot freestream gas and are associated with jet separation from the turbine blade surface. The anti-vortex design is unique in that it requires only easily machinable round holes, unlike shaped film cooling holes and other advanced concepts. The anti-vortex film cooling hole concept has been modeled computationally for a single row of 30deg angled holes on a flat surface using the 3D Navier-Stokes solver Glenn-HT. A modification of the anti-vortex concept whereby the branched holes exit adjacent to the main hole has been studied computationally for blowing ratios of 1.0 and 2.0 and at density ratios of 1.0 and 2.0. This modified concept was selected because it has shown the most promise in recent experimental studies. The computational results show that the modified design improves the film cooling effectiveness relative to the round hole baseline and previous anti-vortex cases, in confirmation of the experimental studies.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215209 , GT2008-50845 , E-16482 , ASME Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 19
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    Benchmarking Gas Path Diagnostic Methods: A Public Approach (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Recent technology reviews have identified the need for objective assessments of engine health management (EHM) technology. The need is two-fold: technology developers require relevant data and problems to design and validate new algorithms and techniques while engine system integrators and operators need practical tools to direct development and then evaluate the effectiveness of proposed solutions. This paper presents a publicly available gas path diagnostic benchmark problem that has been developed by the Propulsion and Power Systems Panel of The Technical Cooperation Program (TTCP) to help address these needs. The problem is coded in MATLAB (The MathWorks, Inc.) and coupled with a non-linear turbofan engine simulation to produce "snap-shot" measurements, with relevant noise levels, as if collected from a fleet of engines over their lifetime of use. Each engine within the fleet will experience unique operating and deterioration profiles, and may encounter randomly occurring relevant gas path faults including sensor, actuator and component faults. The challenge to the EHM community is to develop gas path diagnostic algorithms to reliably perform fault detection and isolation. An example solution to the benchmark problem is provided along with associated evaluation metrics. A plan is presented to disseminate this benchmark problem to the engine health management technical community and invite technology solutions.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215271 , GT2008-51360 , E-16542 , Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 20
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    Automated Power Assessment for Helicopter Turboshaft Engines (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: An accurate indication of available power is required for helicopter mission planning purposes. Available power is currently estimated on U.S. Army Blackhawk helicopters by performing a Maximum Power Check (MPC), a manual procedure performed by maintenance pilots on a periodic basis. The MPC establishes Engine Torque Factor (ETF), an indication of available power. It is desirable to replace the current manual MPC procedure with an automated approach that will enable continuous real-time assessment of available power utilizing normal mission data. This report presents an automated power assessment approach which processes data currently collected within helicopter Health and Usage Monitoring System (HUMS) units. The overall approach consists of: 1) a steady-state data filter which identifies and extracts steady-state operating points within HUMS data sets; 2) engine performance curve trend monitoring and updating; and 3) automated ETF calculation. The algorithm is coded in MATLAB (The MathWorks, Inc.) and currently runs on a PC. Results from the application of this technique to HUMS mission data collected from UH-60L aircraft equipped with T700-GE-701C engines are presented and compared to manually calculated ETF values. Potential future enhancements are discussed.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215270 , E-16541 , 64th Annual Forum and Technology Display (AHS Forum 64); Apr 29, 2008 - May 01, 2008; Montreal; Canada
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  • 21
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    Aircraft Engine On-Line Diagnostics Through Dual-Channel Sensor Measurements: Development of a Baseline System (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: In this paper, a baseline system which utilizes dual-channel sensor measurements for aircraft engine on-line diagnostics is developed. This system is composed of a linear on-board engine model (LOBEM) and fault detection and isolation (FDI) logic. The LOBEM provides the analytical third channel against which the dual-channel measurements are compared. When the discrepancy among the triplex channels exceeds a tolerance level, the FDI logic determines the cause of the discrepancy. Through this approach, the baseline system achieves the following objectives: (1) anomaly detection, (2) component fault detection, and (3) sensor fault detection and isolation. The performance of the baseline system is evaluated in a simulation environment using faults in sensors and components.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215228 , GT2008-50345 , E-16515 , ASME Turbo Expo 2008 Gas Turbine Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 22
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    Preliminary Analysis for an Optimized Oil-Free Rotorcraft Engine Concept (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Recent developments in gas foil bearing technology have led to numerous advanced high-speed rotating system concepts, many of which have become either commercial products or experimental test articles. Examples include Oil-Free microturbines, motors, generators and turbochargers. The driving forces for integrating gas foil bearings into these high-speed systems are the benefits promised by removing the oil lubrication system. Elimination of the oil system leads to reduced emissions, increased reliability, and decreased maintenance costs. Another benefit is reduced power plant weight. For rotorcraft applications, this would be a major advantage, as every pound removed from the propulsion system results in a payload benefit. Implementing foil gas bearings throughout a rotorcraft gas turbine engine is an important long-term goal that requires overcoming numerous technological hurdles. Adequate thrust bearing load capacity and potentially large gearbox applied radial loads are among them. However, by replacing the turbine end, or hot section, rolling element bearing with a gas foil bearing many of the above benefits can be realized. To this end, engine manufacturers are beginning to explore the possibilities of hot section gas foil bearings in propulsion engines. This paper presents a logical follow-on activity by analyzing a conceptual rotorcraft engine to determine the feasibility of a foil bearing supported core. Using a combination of rotordynamic analyses and a load capacity model, it is shown to be reasonable to consider a gas foil bearing core section.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215064 , ARL-TR-4398 , E-16290 , American Helicopter Society 63rd Annual Forum and Technology Display; May 01, 2007 - May 03, 2007; Virginia Beach, VA; United States
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    Design, Fabrication, and Performance of Foil Gas Thrust Bearings for Microturbomachinery Applications (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A methodology for the design and construction of simple foil thrust bearings intended for parametric performance testing and low marginal costs is presented. Features drawn from a review of the open literature are discussed as they relate to bearing performance. The design of fixtures and tooling required to fabricate foil thrust bearings is presented, using conventional machining processes where possible. A prototype bearing with dimensions drawn from the literature is constructed, with all fabrication steps described. A load-deflection curve for the bearing is presented to illustrate structural stiffness characteristics. Start-top cycles are performed on the bearing at a temperature of 425 C to demonstrate early-life wear patterns. A test of bearing load capacity demonstrates useful performance when compared with data obtained from the open literature.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215062 , GT2008-50377 , E-16284 , Turbo Expo 2008 Gas Turbine Technical Congress and Exposition; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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  • 24
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    Pre-Stall Behavior of a Transonic Axial Compressor Stage via Time-Accurate Numerical Simulation (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: CFD calculations using high-performance parallel computing were conducted to simulate the pre-stall flow of a transonic compressor stage, NASA compressor Stage 35. The simulations were run with a full-annulus grid that models the 3D, viscous, unsteady blade row interaction without the need for an artificial inlet distortion to induce stall. The simulation demonstrates the development of the rotating stall from the growth of instabilities. Pressure-rise performance and pressure traces are compared with published experimental data before the study of flow evolution prior to the rotating stall. Spatial FFT analysis of the flow indicates a rotating long-length disturbance of one rotor circumference, which is followed by a spike-type breakdown. The analysis also links the long-length wave disturbance with the initiation of the spike inception. The spike instabilities occur when the trajectory of the tip clearance flow becomes perpendicular to the axial direction. When approaching stall, the passage shock changes from a single oblique shock to a dual-shock, which distorts the perpendicular trajectory of the tip clearance vortex but shows no evidence of flow separation that may contribute to stall.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215163 , ARL-TR-4085 , E-16405 , ASME Turbo Expo 2007; May 14, 2007 - May 17, 2007; Montreal; Canada
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  • 25
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    Modeling of Fixed-Exit Porous Bleed Systems (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A model has been developed to simulate a fixed-exit porous bleed system for supersonic inlets. The fixed-exit model allows the amount of bleed flow to vary according to local flow conditions and fixed-exit characteristics of the bleed system. This variation is important for the control of shock-wave/boundary-layer interactions within the inlet. The model computes the bleed plenum static pressure rather than requiring its specification. The model was implemented in the Wind-US computational fluid dynamics code. The model was then verified and validated against experimental data for bleed on a flat plate with and without an impinging oblique shock and for bleed in a Mach 3.0 axisymmetric, mixed-compression inlet. The model was able to accurately correlate the plenum pressures with bleed rates and simulate the effect of the bleed on the downstream boundary layer. Further, the model provided a realistic simulation of the initiation of inlet unstart. The results provide the most in-depth examination to date of bleed models for use in the simulation of supersonic inlets. The results also highlight the limitations of the models and aspects that require further research.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215178 , AIAA Paper 2008-0094 , E-16423 , 46th AIAA Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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  • 26
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    Distributed Turboelectric Propulsion for Hybrid Wing Body Aircraft (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Meeting future goals for aircraft and air traffic system performance will require new airframes with more highly integrated propulsion. Previous studies have evaluated hybrid wing body (HWB) configurations with various numbers of engines and with increasing degrees of propulsion-airframe integration. A recently published configuration with 12 small engines partially embedded in a HWB aircraft, reviewed herein, serves as the airframe baseline for the new concept aircraft that is the subject of this paper. To achieve high cruise efficiency, a high lift-to-drag ratio HWB was adopted as the baseline airframe along with boundary layer ingestion inlets and distributed thrust nozzles to fill in the wakes generated by the vehicle. The distributed powered-lift propulsion concept for the baseline vehicle used a simple, high-lift-capable internally blown flap or jet flap system with a number of small high bypass ratio turbofan engines in the airframe. In that concept, the engine flow path from the inlet to the nozzle is direct and does not involve complicated internal ducts through the airframe to redistribute the engine flow. In addition, partially embedded engines, distributed along the upper surface of the HWB airframe, provide noise reduction through airframe shielding and promote jet flow mixing with the ambient airflow. To improve performance and to reduce noise and environmental impact even further, a drastic change in the propulsion system is proposed in this paper. The new concept adopts the previous baseline cruise-efficient short take-off and landing (CESTOL) airframe but employs a number of superconducting motors to drive the distributed fans rather than using many small conventional engines. The power to drive these electric fans is generated by two remotely located gas-turbine-driven superconducting generators. This arrangement allows many small partially embedded fans while retaining the superior efficiency of large core engines, which are physically separated but connected through electric power lines to the fans. This paper presents a brief description of the earlier CESTOL vehicle concept and the newly proposed electrically driven fan concept vehicle, using the previous CESTOL vehicle as a baseline.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: 2008 International Powered Lift Conference Royal Aeronautical Society; Jul 22, 2008 - Jul 24, 2008; London; United Kingdom
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  • 27
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    Intelligent Propulsion System Foundation Technology: Summary of Research (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The purpose of this cooperative agreement was to develop a foundation of intelligent propulsion technologies for NASA and industry that will have an impact on safety, noise, emissions, and cost. These intelligent engine technologies included sensors, electronics, communications, control logic, actuators, smart materials and structures, and system studies. Furthermore, this cooperative agreement helped prepare future graduates to develop the revolutionary intelligent propulsion technologies that will be needed to ensure pre-eminence of the U.S. aerospace industry. This Propulsion 21 - Phase 11 program consisted of four primary research areas and associated work elements at Ohio universities: 1.0 Turbine Engine Prognostics, 2.0 Active Controls for Emissions and Noise Reduction, 3.0 Active Structural Controls and Performance, and 4.0 System Studies and Integration. Phase l, which was conducted during the period August 1, 2003, through September 30, 2004, has been reported separately.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215226 , E-16509
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  • 28
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    Intelligent Engine Systems: HPT Clearance Control (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The Advanced Thermally Actuated Clearance Control System underwent several studies. Improved flow path isolation quantified what can be gained by making the HPT case nearly adiabatic. The best method of heat transfer was established, and finally two different borrowed air cooling circuits were evaluated to be used for the HPT Active Clearance Control System.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215234 , E-16493
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  • 29
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    Progress in NASA Rotorcraft Propulsion (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This presentation reviews recent progress made under NASA s Subsonic Rotary Wing (SRW) propulsion research activities. Advances in engines, drive systems and optimized propulsion systems are discussed. Progress in wide operability compressors, modeling of variable geometry turbine performance, foil gas bearings and multi-speed transmissions are presented.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: E-16832 , Fundamental Aeronautics Meeting 2008; Oct 07, 2008 - Oct 09, 2008; Atlanta, GA; United States
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  • 30
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    Comparison of Far-field Noise for Three Significantly Different Model Turbofans (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Far-field noise sound power level (PWL) spectra and overall sound pressure level (OASPL) directivities were compared for three significantly different model fan stages which were tested in the NASA Glenn 9 15 Low Speed Wind Tunnel. The test fans included the Advanced Ducted Propulsor (ADP) Fan1, the baseline Source Diagnostic Test (SDT) fan, and the Quiet High Speed Fan2 (QHSF2). These fans had design rotor tangential tip speeds from 840 to 1474 ft/s and stage pressure ratios from 1.29 to 1.82. Additional parameters included rotor-stator spacing, stator sweep, and downstream support struts. Acoustic comparison points were selected on the basis of stage thrust. Acoustic results for the low tip speed/low pressure ratio fan (ADP Fan1) were thrust-adjusted to show how a geometrically-scaled version of this fan might compare at the higher design thrust levels of the other two fans. Lowest noise levels were typically observed for ADP Fan1 (which had a radial stator) and for the intermediate tip speed fan (Source Diagnostics Test, SDT, R4 rotor) with a swept stator. Projected noise levels for the ADP fan to the SDT swept stator configuration at design point conditions showed the fans to have similar noise levels. However, it is possible that the ADP fan could be 2 to 3 dB quieter with incorporation of a swept stator. Benefits of a scaled ADP fan include avoidance of multiple pure tones associated with transonic and higher blade tip speeds. Penalties of a larger size ADP fan would include increased nacelle size and drag.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM--2008-215136 , AIAA-2008-0049 , E-16299-1 , 46th Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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    Testing of SMA-enabled Active Chevron Prototypes under Representative Flow Conditions (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Control of jet noise continues to be an important research topic. Exhaust-nozzle chevrons have been shown to reduce jet noise, but parametric effects are not well understood. Additionally, thrust loss due to chevrons at cruise suggests significant benefit from active chevrons. The focus of this study is development of an active chevron concept for the primary purpose of parametric studies for jet noise reduction in the laboratory and secondarily for technology development to leverage for full scale systems. The active chevron concept employed in this work consists of a laminated composite structure with embedded shape memory alloy (SMA) actuators, termed a SMA hybrid composite (SMAHC). SMA actuators are embedded on one side of the neutral axis of the structure such that thermal excitation, via joule heating, generates a moment and deflects the structure. The performance of two active chevron concepts is demonstrated in the presence of representative flow conditions. One of the concepts is shown to possess significant advantages for the proposed application and is selected for further development. Fabrication and design changes are described and shown to produce a chevron prototype that meets the performance objectives.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: Paper-6928-36 , LAR-17332 , ASCE 11th Earth and Space Conference; Mar 09, 2008 - Mar 13, 2008; San Diego, cA; United States
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  • 32
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    Damping of High-temperature Shape Memory Alloys (2008)
    In:  CASI
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    Publikationsdatum: 2019-07-13
    Beschreibung: Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: SPIE Smart Materials and Structures Conference; Mar 09, 2008 - Mar 13, 2008; San Diego, CA; United States|Nondestructive Evaluation and Health Monitoring; Mar 09, 2008 - Mar 13, 2008; San Diego, CA; United States
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  • 33
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    Thermal and Environmental Barrier Coating Development for Advanced Propulsion Engine Systems (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Ceramic thermal and environmental barrier coatings (TEBCs) are used in gas turbine engines to protect engine hot-section components in the harsh combustion environments, and extend component lifetimes. Advanced TEBCs that have significantly lower thermal conductivity, better thermal stability and higher toughness than current coatings will be beneficial for future low emission and high performance propulsion engine systems. In this paper, ceramic coating design and testing considerations will be described for turbine engine high temperature and high-heat-flux applications. Thermal barrier coatings for metallic turbine airfoils and thermal/environmental barrier coatings for SiC/SiC ceramic matrix composite (CMC) components for future supersonic aircraft propulsion engines will be emphasized. Further coating capability and durability improvements for the engine hot-section component applications can be expected by utilizing advanced modeling and design tools.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215040 , ARL-TR-4368 , AIAA Paper 2007-2130 , E-16206 , 48th Structures, Structural Dynamics, and Materials Conference; Apr 23, 2008 - Apr 26, 2008; Waikiki, HI; United States
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  • 34
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    Operability of an Ejector Enhanced Pulse Combustor in a Gas Turbine Environment (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: A pressure-gain combustor comprised of a mechanically valved, liquid fueled pulsejet, an ejector, and an enclosing shroud, was coupled to a small automotive turbocharger to form a self-aspirating, thrust producing gas turbine engine. The system was constructed in order to investigate issues associated with the interaction of pulsed combustion devices and turbomachinery. Installed instrumentation allowed for sensing of distributed low frequency pressure and temperature, high frequency pressure in the shroud, fuel flow rate, rotational speed, thrust, and laboratory noise. The engine ran successfully and reliably, achieving a sustained thrust of 5 to 6 lbf, and maintaining a rotor speed of approximately 90,000 rpm, with a combustor pressure gain of approximately 4 percent. Numerical simulations of the system without pressure-gain combustion indicated that the turbocharger would not operate. Thus, the new combustor represented a substantial improvement in system performance. Acoustic measurements in the shroud and laboratory indicated turbine stage sound pressure level attenuation of 20 dB. This is consistent with published results from detonative combustion experiments. As expected, the mechanical reed valves suffered considerable damage under the higher pressure and thermal loading characteristics of this system. This result underscores the need for development of more robust valve systems for this application. The efficiency of the turbomachinery components did not appear to be significantly affected by unsteadiness associated with pulsed combustion, though the steady component efficiencies were already low, and thus not expected to be particularly sensitive.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215169 , AIAA Paper 2008-0119 , E-16410 , 46th Aerospace Sciences Meeting and Exhibit; Jan 07, 2008 - Jan 10, 2008; Reno, NV; United States
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    An Object-oriented Computer Code for Aircraft Engine Weight Estimation (2008)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Reliable engine-weight estimation at the conceptual design stage is critical to the development of new aircraft engines. It helps to identify the best engine concept amongst several candidates. At NASA Glenn (GRC), the Weight Analysis of Turbine Engines (WATE) computer code, originally developed by Boeing Aircraft, has been used to estimate the engine weight of various conceptual engine designs. The code, written in FORTRAN, was originally developed for NASA in 1979. Since then, substantial improvements have been made to the code to improve the weight calculations for most of the engine components. Most recently, to improve the maintainability and extensibility of WATE, the FORTRAN code has been converted into an object-oriented version. The conversion was done within the NASA s NPSS (Numerical Propulsion System Simulation) framework. This enables WATE to interact seamlessly with the thermodynamic cycle model which provides component flow data such as airflows, temperatures, and pressures, etc. that are required for sizing the components and weight calculations. The tighter integration between the NPSS and WATE would greatly enhance system-level analysis and optimization capabilities. It also would facilitate the enhancement of the WATE code for next-generation aircraft and space propulsion systems. In this paper, the architecture of the object-oriented WATE code (or WATE++) is described. Both the FORTRAN and object-oriented versions of the code are employed to compute the dimensions and weight of a 300- passenger aircraft engine (GE90 class). Both versions of the code produce essentially identical results as should be the case. Keywords: NASA, aircraft engine, weight, object-oriented
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: GT2008-50062 , Proceedings of ASME Turbo Expo 2008: Power for Land, Sea and Air; Jun 09, 2008 - Jun 13, 2008; Berlin; Germany
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    A Cryogenic High-Power-Density Bearingless Motor for Future Electric Propulsion (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: The NASA Glenn Research Center (GRC) is developing a high-power-density switched-reluctance cryogenic motor for all-electric and pollution-free flight. However, cryogenic operation at higher rotational speeds markedly shortens the life of mechanical rolling element bearings. Thus, to demonstrate the practical feasibility of using this motor for future flights, a non-contact rotor-bearing system is a crucial technology to circumvent poor bearing life that ordinarily accompanies cryogenic operation. In this paper, a bearingless motor control technology for a 12-8 (12 poles in the stator and 8 poles in the rotor) switched-reluctance motor operating in liquid nitrogen (boiling point, 77 K (-196 C or -321 F)) was presented. We pushed previous disciplinary limits of electromagnetic controller technique by extending the state-of-the-art bearingless motor operating at liquid nitrogen for high-specific-power applications. The motor was levitated even in its nonlinear region of magnetic saturation, which is believed to be a world first for the motor type. Also we used only motoring coils to generate motoring torque and levitation force, which is an important feature for developing a high specific power motor.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215211 , E-16485 , Paper no. 3114 , 2008 Propulsion-Safety and Affordable Readiness (P-SAR) Conference; Mar 19, 2008 - Mar 20, 2008; Myrtle Beach, SC; United States
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    The General Aviation Propulsion (GAP) Program (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The General Aviation Propulsion (GAP) Program Turbine Engine Element focused on the development of an advanced small turbofan engine. Goals were good fuel consumption and thrust-to-weight ratio, and very low production cost. The resulting FJX-2 turbofan engine showed the potential to meet all of these goals. The development of the engine was carried through to proof of concept testing of a complete engine system. The proof of concept engine was ground tested at sea level and in altitude test chambers. A turboprop derivative was also sea-level tested.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215266 , E-16536
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  • 38
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    Aerodynamic Design of a Dual-Flow Mach 7 Hypersonic Inlet System for a Turbine-Based Combined-Cycle Hypersonic Propulsion System (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A new hypersonic inlet for a turbine-based combined-cycle (TBCC) engine has been designed. This split-flow inlet is designed to provide flow to an over-under propulsion system with turbofan and dual-mode scramjet engines for flight from takeoff to Mach 7. It utilizes a variable-geometry ramp, high-speed cowl lip rotation, and a rotating low-speed cowl that serves as a splitter to divide the flow between the low-speed turbofan and the high-speed scramjet and to isolate the turbofan at high Mach numbers. The low-speed inlet was designed for Mach 4, the maximum mode transition Mach number. Integration of the Mach 4 inlet into the Mach 7 inlet imposed significant constraints on the low-speed inlet design, including a large amount of internal compression. The inlet design was used to develop mechanical designs for two inlet mode transition test models: small-scale (IMX) and large-scale (LIMX) research models. The large-scale model is designed to facilitate multi-phase testing including inlet mode transition and inlet performance assessment, controls development, and integrated systems testing with turbofan and scramjet engines.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215214 , E-16505 , TRR-121507
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  • 39
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    Demonstration of Active Combustion Control (2008)
    In:  CASI
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    Publikationsdatum: 2019-07-12
    Beschreibung: The primary objective of this effort was to demonstrate active control of combustion instabilities in a direct-injection gas turbine combustor that accurately simulates engine operating conditions and reproduces an engine-type instability. This report documents the second phase of a two-phase effort. The first phase involved the analysis of an instability observed in a developmental aeroengine and the design of a single-nozzle test rig to replicate that phenomenon. This was successfully completed in 2001 and is documented in the Phase I report. This second phase was directed toward demonstration of active control strategies to mitigate this instability and thereby demonstrate the viability of active control for aircraft engine combustors. This involved development of high-speed actuator technology, testing and analysis of how the actuation system was integrated with the combustion system, control algorithm development, and demonstration testing in the single-nozzle test rig. A 30 percent reduction in the amplitude of the high-frequency (570 Hz) instability was achieved using actuation systems and control algorithms developed within this effort. Even larger reductions were shown with a low-frequency (270 Hz) instability. This represents a unique achievement in the development and practical demonstration of active combustion control systems for gas turbine applications.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215491 , E-16813
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  • 40
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    Post Test Evaluation of HSCT Nozzle Acoustic Liner Subcomponents Subjected to a Hot Acoustic Durability Test (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The acoustic liner system designed for use in the High Speed Civil Transport (HSCT) was tested in a thermal-acoustic environment. Five ceramic matrix composite (CMC) acoustic tile configurations, five bulk acoustic absorbers, and one thermal protection system design were tested. The CMC acoustic tiles were subjected to two 2 3/4 hr ambient temperature acoustic exposures to measure their dynamic response. One exposure was conducted on the tiles alone and the second exposure included the tiles and the T-foam bulk absorber. The measured tile RMS strains were small. With or without the T-foam absorber, the dynamic strains were below strain levels that would cause damage during fatigue loading. After the ambient exposure, a 75-hr durability test of the entire acoustic liner system was conducted using a thermal-acoustic cycle that approximated the anticipated service cycle. Acoustic loads up to 139 dB/Hz and temperatures up to 1670 F (910 C) were employed during this 60 cycle test. During the durability test, the CMC tiles were exposed to temperatures up to 1780 F and a transient through thickness gradient up to 490 F. The TPS peak temperatures on the hot side of the panels ranged from 750 to 1000 F during the 60 cycles. The through thickness delta T ranged from 450 to 650 F, varying with TPS location and cycle number. No damage, such as cracks or chipping, was observed in the CMC tiles after completion of the testing. However, on tile warped during the durability test and was replaced after 43 or 60 cycles. No externally observed damage was found in this tile. No failure of the CMC fasteners occurred, but damage was observed. Cracks and missing material occurred, only in the fastener head region. No indication of damage was observed in the T-foam acoustic absorbers. The SiC foam acoustic absorber experienced damage after about 43 cycles. Cracking in the TPS occurred around the attachment holes and under a vent. In spite of the development of damage, the TPS maintained its insulative capability throughout the durability test. The durability test results demonstrate damage-tolerant CMC tile, CMC fastener, TPS, and T-foam absorber designs for the combined thermal and acoustic engine nozzle environment.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM--2008-215015 , E-16184 , HSR075
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  • 41
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    Mixing of Multiple Jets with a Confined Subsonic Crossflow: Part III--The Effects of Air Preheat and Number of Orifices on Flow and Emissions in an RQL Mixing Section (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: This study was motivated by a goal to understand the mixing and emissions in the Rich-burn/Quick-mix/Lean-burn (RQL) combustor scheme that has been proposed to minimize the formation of oxides of nitrogen (NOx) in gas turbine combustors. The study reported herein was a reacting jet-in-crossflow experiment at atmospheric pressure. The jets were injected from the perimeter of a cylindrical duct through round-hole orifices into a fuel-rich mainstream flow. The number of orifices investigated in this study gave over- to optimum to underpenetrating jets at a jet-to-mainstream momentum-flux ratio of J = 57. The size of individual orifices was decreased as the number of orifices increased to maintain a constant total area; the jet-to-mainstream mass-flow ratio was constant at MR = 2.5. The experiments focused on the effects of the number of orifices and inlet air preheat and were conducted in a facility that provided the capability for independent variation of jet and main inlet air preheat temperature. The number of orifices was found to have a significant effect on mixing and the distributions of species, but very little effect on overall NOx emissions, suggesting that an aerodynamically optimum mixer might not minimize NOx emissions. Air preheat was found to have very little effect on mixing and the distributions of major species, but preheating both main and jet air did increase NOx emissions significantly. Although the air jets injected in the quick-mix section of an RQL combustor may comprise over 70 percent of the total air flow, the overall NOx emission levels were found to be more sensitive to main stream air preheat than to jet stream air preheat.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215151 , E-16378
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  • 42
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    Halbach Magnetic Rotor Development (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The NASA John H. Glenn Research Center has a wealth of experience in Halbach array technology through the Fundamental Aeronautics Program. The goals of the program include improving aircraft efficiency, reliability, and safety. The concept of a Halbach magnetically levitated electric aircraft motor will help reduce harmful emissions, reduce the Nation s dependence on fossil fuels, increase efficiency and reliability, reduce maintenance and decrease operating noise levels. Experimental hardware systems were developed in the GRC Engineering Development Division to validate the basic principles described herein and the theoretical work that was performed. A number of Halbach Magnetic rotors have been developed and tested under this program. A separate test hardware setup was developed to characterize each of the rotors. A second hardware setup was developed to test the levitation characteristics of the rotors. Each system focused around a unique Halbach array rotor. Each rotor required original design and fabrication techniques. A 4 in. diameter rotor was developed to test the radial levitation effects for use as a magnetic bearing. To show scalability from the 4 in. rotor, a 1 in. rotor was developed to also test radial levitation effects. The next rotor to be developed was 20 in. in diameter again to show scalability from the 4 in. rotor. An axial rotor was developed to determine the force that could be generated to position the rotor axially while it is rotating. With both radial and axial magnetic bearings, the rotor would be completely suspended magnetically. The purpose of this report is to document the development of a series of Halbach magnetic rotors to be used in testing. The design, fabrication and assembly of the rotors will be discussed as well as the hardware developed to test the rotors.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215056 , E-16281
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  • 43
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    Enhanced Self Tuning On-Board Real-Time Model (eSTORM) for Aircraft Engine Performance Health Tracking (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: A key technological concept for producing reliable engine diagnostics and prognostics exploits the benefits of fusing sensor data, information, and/or processing algorithms. This report describes the development of a hybrid engine model for a propulsion gas turbine engine, which is the result of fusing two diverse modeling methodologies: a physics-based model approach and an empirical model approach. The report describes the process and methods involved in deriving and implementing a hybrid model configuration for a commercial turbofan engine. Among the intended uses for such a model is to enable real-time, on-board tracking of engine module performance changes and engine parameter synthesis for fault detection and accommodation.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215272 , FR-26751 , E-16543
    Format: application/pdf
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  • 44
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    System Study for Axial Vane Engine Technology (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-12
    Beschreibung: The purpose of this engine feasibility study was to determine the benefits that can be achieved by incorporating positive displacement axial vane compression and expansion stages into high bypass turbofan engines. These positive-displacement stages would replace some or all of the conventional compressor and turbine stages in the turbine engine, but not the fan. The study considered combustion occurring internal to an axial vane component (i.e., Diesel engine replacing the standard turbine engine combustor, burner, and turbine); and external continuous flow combustion with an axial vane compressor and an axial vane turbine replacing conventional compressor and turbine systems.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/CR-2008-215175 , E-16418
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  • 45
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    Assessment of Microphysical Models in the National Combustion Code (NCC) for Aircraft Particulate Emissions: Particle Loss in Sampling Lines (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: This paper at first describes the fluid network approach recently implemented into the National Combustion Code (NCC) for the simulation of transport of aerosols (volatile particles and soot) in the particulate sampling systems. This network-based approach complements the other two approaches already in the NCC, namely, the lower-order temporal approach and the CFD-based approach. The accuracy and the computational costs of these three approaches are then investigated in terms of their application to the prediction of particle losses through sample transmission and distribution lines. Their predictive capabilities are assessed by comparing the computed results with the experimental data. The present work will help establish standard methodologies for measuring the size and concentration of particles in high-temperature, high-velocity jet engine exhaust. Furthermore, the present work also represents the first step of a long term effort of validating physics-based tools for the prediction of aircraft particulate emissions.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215304 , AIAA Paper-2009-0257 , E-16575 , 47th AIAA Aerpspace Sciences Meeting (ASM); Jan 05, 2009 - Jan 08, 2009; Florida; United States
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  • 46
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    Multiplexed Predictive Control of a Large Commercial Turbofan Engine (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Model predictive control is a strategy well-suited to handle the highly complex, nonlinear, uncertain, and constrained dynamics involved in aircraft engine control problems. However, it has thus far been infeasible to implement model predictive control in engine control applications, because of the combination of model complexity and the time allotted for the control update calculation. In this paper, a multiplexed implementation is proposed that dramatically reduces the computational burden of the quadratic programming optimization that must be solved online as part of the model-predictive-control algorithm. Actuator updates are calculated sequentially and cyclically in a multiplexed implementation, as opposed to the simultaneous optimization taking place in conventional model predictive control. Theoretical aspects are discussed based on a nominal model, and actual computational savings are demonstrated using a realistic commercial engine model.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: E-16761 , AIAA Journal of Guidance, Control, and Dynamics (ISSN 0731-5090); 31; 2; 273-281
    Format: application/pdf
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  • 47
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    Concepts for Variable/Multi-Speed Rotorcraft Drive System (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: In several recent studies and on-going developments for advanced rotorcraft, the need for variable or multi-speed capable rotors has been raised. A speed change of up to 50 percent has been proposed for future rotorcraft to improve overall vehicle performance. Accomplishing rotor speed changes during operation requires both a rotor that can perform effectively over the operation speed/load range, and a propulsion system that can enable these speed changes. A study has been completed to investigate possible drive system arrangements that can accommodate up to the 50 percent speed change. Several concepts will be presented and evaluated. The most promising configurations will be identified and developed for future testing in a sub-scaled test facility to validate operational capability.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: NASA/TM-2008-215276 , ARL-TR-4564 , AHS 080273 , 64th Annual Forum and Technology Display (American Helicopter Society Forum); Apr 29, 2008 - May 01, 2008; Montreal; Canada
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  • 48
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    NASA / Pratt and Whitney Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Current collaborative research with Pratt & Whitney on Ultra High Bypass Engine Cycle noise, performance and emissions improvements as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. Progress toward achieving the Subsonic Fixed Wing Project goals over the 2008 fiscal year by the UHB Partnership in this area of research are reviewed. The current research activity in Ultra High Bypass Engine Cycle technology, specifically the Pratt & Whitney Geared Turbofan, at NASA and Pratt & Whitney are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. Pratt & Whitney Geared Turbofan current and future technology and business plans are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: E-16905 , Fundamental Aeronautics Program - 2nd Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Georgia; United States
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  • 49
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    NASA / GE Aviation Collaborative Partnership Research in Ultra High Bypass Cycle Propulsion Concepts (2008)
    In:  CASI
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Current collaborative research with General Electric Aviation on Open Rotor propulsion as part of the Subsonic Fixed Wing Project Ultra High Bypass Engine Partnership Element is discussed. The Subsonic Fixed Wing Project goals are reviewed, as well as their relative technology level compared to previous NASA noise program goals. The current Open Rotor propulsion research activity at NASA and GE are discussed including the contributions each entity bring toward the research project, and technical plans and objectives. GE Open Rotor propulsion technology and business plans currently and toward the future are also discussed, including the role the NASA SFW UHB partnership plays toward achieving those goals.
    Schlagwort(e): Aircraft Propulsion and Power
    Materialart: E-16903 , FA Annual Meeting; Oct 07, 2008 - Oct 09, 2008; Georgia; United States
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  • 50
    Digitale Medien
    Digitale Medien
    Masthead (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990) 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230101
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  • 51
    Digitale Medien
    Digitale Medien
    Chrom-Komplexe mit cyclo-Asx-Liganden (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 3-6 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Pentaarsacyclopentadienyl ligand / Triarsachromatertrahedranes / Triple-decker complexes / Tetrahedrane, triarsachroma- ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Chromium Complexes with cyclo-Asx, LigandsThe interaction of [(η5C5Me4R)(CO)2Cr]2(Cr≡Cr) (1a: R = CH3 1b: R = C2H5) with yellow arsenic (As4) affords the triarsachromatetrahedranes [(η5-C5Me4R)(CO)2Cr(η3-As3)] (2a, b) as well as the 27-VE triple-decker complexes [{(η5-C5Me4R)Cr}2-(μ,η5-As5)] (3a, b) 3 is also formed photochemically from 2. 2a and 3b have been characterized by X-ray structure analyses. The cyclo-As5 ligand forms a regular arsenic pentagon.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230102
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  • 52
    Digitale Medien
    Digitale Medien
    Bindung von Monosacchariden über die Isocyano- und Carben-Funktion an das Metall-Atom: Chrom(0), Wolfram(0)-, Rhodium(III)-, Iridium(III)-, Palladium(II)-, Platin(II)- und Gold(I)-Komplexe von 1,3,4,6-Tetra-O-acetyl-2-desoxy-2-isocyano-α-D-glucose und - β-D-glucose (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 11-17 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Isocyanide complexes / Carbene complexes / Transition metal complexes / Carbohydrates / Glucose, 2-deoxy-2-isocyano-, as complex ligand ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Metal-Complexes of Biologically Important Ligands, LII. - Binding of Monosaccharides through the Isocyano and Carbene Group to the Metal Atom: Chromium(O), Tungsten(O), Rhodium(III), Iridium(1II). Palladium(I1). Platinum(ZI), and Gold(1) Complexes of 1.3.4.6-Tetra-O-acetyl-2-deoxy-2-isocyano-α-D-glucose and -β-D-glucoseStable isocyanide complexes cis-Cl2Pd(CNR)2 (2), cis-Cl2Pt(CNR)2 (3), cis-Cl2Pt(PPh3)CNR (4), [trans-(Ph3P)2Pt(Cl)CNR]+BF-4 (5), ClAuCNR (6), (OC)5CrCNR (7), (OC)5WCNR (8), (η5-C5Me5)Rh-(CNR)Cl2 (9), (η5-C5Me5)Ir(CNR)Cl2 (10) of 1,3,4,6-tetra-O-acetyl-2-deoxy-2-isocyano-α(β)-D-glucose (CNR) as well as carbene complexes ClAuC(NHR')(NHR) (11, 12) and cis-Cl2Pt(PPh3)C-(OR')NHR (13, 14) have been prepared and characterized by their IR and NMR spectra. The structure of 10 has been determined by X-ray crystal structure analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230104
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  • 53
    Digitale Medien
    Digitale Medien
    Übergangsmetall-substituierte Acylphosphane und Phosphaalkene, XII1. - Übergangsmetall-Schwefelylid-Komplexe, XXVII2) Zur Umwandlung des Phosphaalkenyleisen-Komplexes (η5-C5Me5)-(CO)2FeP=C(SiMe3) 2 in η3-Phosphaallyleisen-Komplexe mittels Me2S(O)=CH2: Synthese und Molekülstruktur der beiden Isomeren von (η5-C5Me5)(CO)Fe{η3-P[CH(SiMe3)2](CHC=O)} (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 23-28 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphaallyl complexes / Sulfur ylides ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transition-Metal-Substituted Acylphosphines and Phosphaalkenes. XII. - Transition-Metal Sulfur Ylide Complexes, XXVIIzt - Conversion of a Phosphaalkenyliron Complex (η5-C5Me5)-(CO)2FeP=(SiMe3)2 into (η3-Phosphaallyl)iron Complexes by means of Me2S-(O)=CH2: Synthesis and Molecular Structures of Two Isomeres of (η5-C5Me5)-(CO)η5-P(CH-(SiMe3)2(CHC-0)}The transition-metal-substituted phosphaalkene (η5-C5Me5)-(CO)2FeP=C(SiMe3)2 (1) reacts with the sulfur ylide Me2S-(O)=CH2 (2) to afford the yellow η3-phosphaallyliron complex 4 with a syn-configuration in the organophosphorus ligand. In toluene solution at 40°C this complex undergoes an isomerization to the corresponding anti-configurated complex 5. Constitution and configuration of both compounds were elucidated by spectroscopic methods (IR, 1H, 13C, 31P NMR, and MS) as well as single-crystal X-ray diffraction analyses.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230106
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  • 54
    Digitale Medien
    Digitale Medien
    Diphosphabicyclobutane (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 67-69 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diphosphabicyclobutanes / Valence isomerization ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: DiphosphabicyclobutanesTwo isomeric diphosphabicyclobutanes (5,11) are obtained by treatment of the phosphaalkenes X-P = C(Ph)Tms (1a) and X - P = CTms2 (1b) (X = halogen Tms = trimethylsilyl) with 2, Mg, or Na. Both syntheses proceed by coupling of two phosphaalkene units affording, however, two different diphospha-butadiene intermediates. 4 and 10 readily undergo isomerization reactions to form the diphosphabicyclobutanes. Irradiation of the phosphaalkenes Cp* - P = C(Ph)Tms (12a) and Cp* - P = CTms2 (12b) (Cp* = C5Me5) gives rise to a different reaction pathway. Dimerization of 12a, followed by homolytic cleavage of the Cp* - phosphorus bond and intramolecular recombination produces the butterfly compound 5, whereas homolytic cleavage of the Cp* - element bond in 12 b, followed by rearrangement and intermolecular recombination, affords the diphosphabicyclobutane 11.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230113
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  • 55
    Digitale Medien
    Digitale Medien
    Mononuclear Bis(diazadiene)ruthenium(0) Complexes and the Coupling of Butadiene to a Diazadiene System (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 83-85 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diazadienes/Carbon-carbon coupling/Ruthenium(0) complexes/Ethylene complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Complexes (dad)2RuCl2 (1) (dad = diazadiene, RN = CR'- CR'=NR) are reduced to (dad)2Ru (2) which react with L = CO or ethylene to give (dad)2RuL (3,5). Reduction of 1b ( R' = H) with magnesium-butadiene or reaction of 2b with butadiene leads to a new type of C-C coupling of butadiene to one of the diazadiene ligands (6b). Addition of CO induces a rearrangement to 7b by a hydride shift.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230117
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  • 56
    Digitale Medien
    Digitale Medien
    Light-Induced Conversion of 4,6,7,8-Tetrahydro-2H-benzopyran-2,5(3H)-diones into 3,5,6,7-Tetrahydrobenzofuran-4(2H)-ones in Methanol (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 101-105 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Enol lactones, photochemistry of / Ketene photoextrusion / Ketones, photoreduction / 0-Heterocycles, photochemistry of ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photochemical conversion of 4,4,7,7-tetramethyl-4,6,7,8-tetrahydro-2H-benzopyran-2,5(3H)-dione (1) into 3,3,6,6-tetramethyl-3,5,6,7-tetrahydrobenzofuran-4(2H)-one (4) in methanol does not - as previously assumed - proceed by decarbonylation of the primarily formed acyl-vinyloxy biradical 2. This conclusion results from the finding that C-2, i. e. the CH2 group, of benzofuranone 4 stems from the solvent. Similar observations were made for other benzopyrandiones 15. A reaction sequence consisting of (a) ketene elimination from 2 with formation of 2-isopropylidene-5,5-dimethyl-1,3-cyclo-hexanedione and (b) light-induced (reductive) H . and . CH2OH addition to this intermediate followed by cyclization and dehydration to 4, is proposed for the conversion 1→4.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230121
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  • 57
    Digitale Medien
    Digitale Medien
    Synthese von Sieben- und Achtring-anellierten Pyridinen durch “inverse” intramolekulare Diels-Alder-Reaktion mit Trifluormethyl-substituierten 1,2,4-Triazinen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 133-136 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 1,2,4-Triazines / Dienophiles, side-chain / [4+21 Cycloaddition / Pyrido[2,3-e-l,4-diazepines / Pyrido[2,3-b]-1,5-diazocines ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Seven- and Eight-Membered Ring-Annulated Pyridines by “Inverse” Intramolecular Diels-Alder Reaction with Trifluoromethyl-Substituted 1,2,4-TriazinesIntramolecular [4 + 2] cycloaddition reactions with inverse electron demand of trifluoromethyl-substituted 1,2,4-triazines carrying 7- or 8-membered o-alkyne side-chain dienophiles (3,8,12) lead to the synthesis of bicyclic pyridines with annulated heterocyclic seven- (5, 9, 13-15) or eight-membered rings (19, 22, 23, 26).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230125
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  • 58
    Digitale Medien
    Digitale Medien
    Synthesen und Strukturen neuer Komplexes des 2,2′-Bipyridins mit Niob, Molybdän, Wolfram und Rhenium in hohen Oxidationsstufen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 271-276 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Niobium complexes / Molybdenum complexes / Tungsten complexes / Rhenium complexes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Syntheses and Structures of New 2,2′-Bipyridine Complexes of Niobium, Molybdenum, Tungsten, and Rhenium in High Oxidation StatesExchange of oxo for chlorine ligands by means of hexamethyl-disiloxane provides an easy and effective synthesis of the oxo halides (bipy)MVOCl3 (bipy = 2,2′-bipyridine, C10H8N2; M = Nb, 1c; Re, 2c; W, 3c) and (bipy)MVIO2Cl2 (N = Mo, 6a;W, 6b). Starting from ReCl5 the structurally (X-ray) characterized byproduct (bipy)ReIVCl4 (2b) is also formed. Dirhenium heptaoxide (7) is converted into the complex (bipy)ReVIIO3Cl (8) upon treatment with chlorotrimethylsilane in the presence of 2,2′-bipyridine, thus being now easily available a key compound in rhenium chemistry. The new imido complexes of composition (bipy)MoVI(NR)2Cl2 [R = C(H3)3, 9a; C6H5, 9b] are accessible from 6a and the corresponding silylated amines. The rhenium and tungsten complexes 2b and 6b, resp., exhibit octahedral structures in the crystal, with that of 6b being distorted as a result of different ligands and intermolecular contacts.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230208
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  • 59
    Digitale Medien
    Digitale Medien
    Ungewöhnliche Reaktion eines Diazaphosphetidinthions mit Trimethylsilylazid (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 289-292 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diazaphosphetidinethione / Trimethylsilyl azide / Migration, methyl group, trimethylsilyl group ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Unusual Reaction of a Diazaphosphetidinethione with Trimethylsilyl Azide2-Dimethylamino-1,3-dimethyl-1,3-diaza-2-phosphetidine-4-thione (1) and trimethylsilyl azide do not react with formation of the expected phosphane imine 2. Instead, (a) addition of trimethylsilyl azide to the °C=S group of 1, (b) sulfurization of the phosphorus atom of 1 and formation of the racemic thiophosphoryl compound 3 (as a result of intramolecular methyl/trimethylsilyl migration) take place. For 3 two pairs of diastereomers are discussed, which have been studied by 1H-, 13C- and 31P-NMR spectroscopy, and through a 1H-13C NMR correlation.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230211
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  • 60
    Digitale Medien
    Digitale Medien
    Photo Diels-Alder Additons, V1 1,4-Photoadditions of α-Morpholinoacrylonitrile to 1-Acylnaphthalenes (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 315-319 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Cycloadditions, regio- and stereoselective, light-induced / 1,4-Ethanonaphthalenes / Captodative alkenes / Di-π-methane rearrangement ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photoexcited 1-naphthaldehyde (1a), 1-acetonaphthone (1b), and 1-naphthophenone (1c) add α-morpholinoacrylonitrile (2a) in a [4 + 2] mode with exceptional regio- and stereoselective formation of only one diastereomer of the two possible regioisomeric 1,4-dihydro-1,4-ethanonaphthalene adducts. An independently formed 1,2-adduct 4 was detected and isolated in very low yield, 4 is thermally and photochemically (313-nm, excitation) cleaved into the starting materials with no indication of direct interconversion into 3b. Compound 3b is stable towards 313-nm radiation, but is efficiently isomerized to give the dihydrobenzosemibullvalene 7 upon 254-nm excitation. - All observations point to the first excited triplet state as the starting point for the 1,4-additions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230216
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  • 61
    Digitale Medien
    Digitale Medien
    Stereochemistry of Dewar Benzenes - Molecular Structures Influenced by Electronic and Steric Effects (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 345-350 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Dewar benzene, derivatives, molecular structures of / Substituent effects on molecular structure ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The molecular structures of the four Dewar benzene derivatives 4-7 were determined by means of X-ray diffraction. The central C1-C4 bonds are extremely long. The carboxylate groups on the bridgehead carbon atoms of 4, 5, and 7 are in optimal orientation for an electronic interaction with the central bonds having high p-character. Therefore the central bonds in 4, 5, und 7 (1.602-1.612 Å) are even more elongated than in 6 (1.563 Å). Repulsion between tert-butyl groups causes bond lengthening and structural deformations. The sp2-hybridized carbon atoms are pyramidalized. From structural comparison of Dewar benzene derivatives a strong correlation between the length of the central bond and the folding angle of the four-membered rings can be derived. A new rule has been established for the thermal stability of Dewar benzene derivatives.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230220
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  • 62
    Digitale Medien
    Digitale Medien
    Neue wasserlösliche makrobicyclische Großhohlräume (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 375-379 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Cyclophanes / Hostguest chemistry / Macrocyclic compounds / Phanes / Supramolecular chemistry ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: New Watersoluble Macrobicyclic CavitiesThe watersoluble macrobicyclic compounds 1, 3, 5a, and 5b have been synthesized for the first time bearing large endolipophilic cavities of different sizes and shapes. They were studied with respect to their interactions towards lipophilic guest compounds. The “in/out” isomerism of the hitherto largest endolipophilic cavities 4a, 4b, 5a, and 5b has been investigated by 1H-, 13C-NMR spectroscopy and FAB mass spectrometry. The absence of significant 1H-NMR high-field shifts in hostguest studies is attributed to the rigidity of cavities 1 and 3, whilst the isomeric cavities 5a and 5b contain very large openings. Orientational fluorescence spectroscopy investigations, however, suggest hostguest interactions of the isomers 5a and 5b with ammonium 8-anilino-1-naphthalenesulfonate (8,1-ANS).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230224
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  • 63
    Digitale Medien
    Digitale Medien
    Elektrophile β-Bromierung und nucleophile α-Methoxylierung α,β-ungesättigter Carbonylverbindungen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 399-404 
    Details
    ISSN: 0009-2940
    Schlagwort(e): β-Halovinyl ketones / β-Halovinyl aldehydes / α-Alkoxyvinyl ketones ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Electrophilic β-Bromination and Nucleophilic α-Methoxylation of α,β-Unsaturated Carbonyl CompoundsOximes 29a, b, semicarbazones 11a-d, dimethylhydrazones 4, and [3-methyl-2(3H)-benzothiazolylidene]hydrazones 23a-c of unsaturated aldehydes and ketones are brominated at the β-carbon by an addition-elimination sequence (→ 21a,b, 13a-d, 7, and 27c, respectively). When unsaturated ketone hydrazones are treated with bromine and methanol the α-methoxy-β-bromo derivatives 35a-c are obtained, which after hydrolysis and hydrobromic acid elimination give α-methoxy substitution products 36a-c of the starting compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230227
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  • 64
    Digitale Medien
    Digitale Medien
    Electron-Density Distribution in the Bonds of a Dewar Benzene Derivative (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 341-343 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Difference electron densities / Dewar benzene, derivative ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: We determined the difference electron densities [X-X] in the bonds of a Dewar benzene derivative from low temperature X-ray data (94 K). The density maxima on all bonds are significant. The central bond with an internuclear distance of 1.594 Å has a strong bending character. From the difference densities a bending angle of 28° can be derived.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230219
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  • 65
    Digitale Medien
    Digitale Medien
    Zur Stereoselektivität der intramolekularen Diels-Alder-Reaktion von 1,7,9-Decatrien-3-onen zu Octalonderivaten (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 363-374 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diels-Alder reaction, intramolecular / 1,7,9-Decatrien-3-ones / Octalone derivatives / Siloxycyclopropanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Stereoselectivity of Intramolecular Diels-Alder Reactions of 1,7,Q-Decatrien-3-ones to Octalone Derivatives2-Alkenyl-substituted 2-siloxycyclopropanes 1 and 2 serve as protected enone equivalents and are converted into key building blocks 5-8 in excellent yields. After desilylation and ring cleavage these compounds provide 1,7,9-decatrien-3-ones 9-12, which undergo smooth intramolecular Diels-Alder reaction at room temperature or approximately 100°C. The resulting octalone derivatives 13-16 are formed with exclusive or preferred cis connection of the rings. The relative configurations of the cycloadducts are secured by equilibration experiments and NMR spectroscopy (selective proton decouplings). For 11 → 15 and 12 → 16 the cis selectivitiy can remarkably be enhanced by trifluoroacetic acid catalysis. This high noninduced diastereoselectivity is caused by the endo approach of the reactive molecular sites, whereas the configuration of the third stereogenic centre (C-2) is determined by the folding of the linking carbon chain. Preference of a boat conformation with equatorial ester group endo-Beq may be assumed and appears to be general for intramolecular cycloadditions of such trienones. This effect as well as the influence of further substituents at the diene or dienophile portion on stereoselectivity and the reactions of other model compounds are discussed.
    Zusätzliches Material: 8 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230223
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  • 66
    Digitale Medien
    Digitale Medien
    Novel Access to Polyazamacrocycles: Non-Template Cyclization of Terephthalaldehyde and Aliphatic Polyamines (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 405-406 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Polyazamacrocycles / Cyclization, non-template / Terephthalaldehyde / Polyamines ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Non-template [2+2] condensation of terephthalaldehyde with bis(3-aminopropyl)amine and N,N'-bis(3-aminopropyl)-1,2-diaminoethane leads to macrocyclic systems that can be reduced and derivatized further, whereas a similar reaction with bis(2-aminoethyl)amine leads to polymeric material only.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230228
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  • 67
    Digitale Medien
    Digitale Medien
    Deuterierte Bicyclo[3.2.0]heptan-2-one und ihre NMR-Spektren (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 411-412 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Bicyclo[3.2.0]heptan-2-one, deuterated ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Deuterated Bicyclo[3.2.0]heptan-2-ones and their NMR Spectra[3,3-2H2]-, [6,7-2H2]-, [6,6-2H2]-, and [7,7-2H2]bicyclo[3.2.0]heptan-2-ones were prepared, starting from 2-cyclopenten-1-one (1). Using these derivatives, the 13C- and 1H-NMR spectra of bicyclo[3.2.0]heptan-2-one (2) have been assigned.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230230
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  • 68
    Digitale Medien
    Digitale Medien
    Die Borierung von Lactamen und Harnstoffen mit einem Amino-imino-boran (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 455-458 
    Details
    ISSN: 0009-2940
    Schlagwort(e): N-Boryl lactams / Isourea, triborated / Isothiourea, triborated /N/O Borotropism / Calculations, MNDO ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Contribution to the Chemistry of Boron, 201. - Boration of Lactams and Ureas by an Amino-Imino-BoranePyrrolidon reacts with (tert-butylimino)(2,2,6,6-tetramethylpiperidino)borane (1) to give the N-borated lactam 2. Diketopiperazine behaves similarly. It is borated on both of its N atoms to form 3. Urea and 1 give access to the O,N,N′-triborated isourea derivative 4, which contains the structural unit of a ketiminoborane. The diborated carbodiimide 10 is ultimately obtained from 1 and thiourea via the triborated isothiourea derivative 9. MNDO calculations have been used to estimate the relative thermodynamic stabilities of O/N borotropes of carbonic acid amides and lactams. They demonstrate that the O isomers gain in stability by increasing the size of N substituents.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230307
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  • 69
    Digitale Medien
    Digitale Medien
    Lithium-Verbindungen eines Chlorsilanols und von Fluor-funktionellen Siloxanolen; Reaktionen und Kristallstrukturen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 449-453 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Lithium salts / Chlorosilanol / Fluorosilanolates ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Lithium Compounds of a Chlorosilanol and of Fluoro-Functional Siloxanols; Synthesis and Crystal StructuresThe lithiated disilanol (CMe3)2Si(OH)2 (1) serves as a starting material in the reaction with halosilanes for the stepwise construction of siloxanols (4, 5, 7). 4 and 7 react with n-C4H9Li to give the lithium compounds 6 and 8, respectively. 6 crystallizes in hexane as a trimer with planar three-coordinated lithium, bonded to two Si-O atoms and one Si - F atom. 8 reacts in THF with LiF elimination to give cyclotrisiloxane 9. The chlorosilanol 2 is prepared by hydroxy-chlorine exchange in 1 with PCl5. The stable lithium derivative of 2 (3) forms a dimeric THF adduct with tetrahedral lithium.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230306
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  • 70
    Digitale Medien
    Digitale Medien
    Chemistry of the Heterocyclic Pseudobasic Amino Alcohols, XXXVIII Ring-Chain Tautomerism of Pyrimido[6,1-a]isoquinolines (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 493-498 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Pyrimido[6,1-a]isoquinolines / Pseudobases, heterocyclic / Ring-chain tautomerism ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: In basis media, 4-substituted pyrimido[6,1-a]isoquinolin-2-imine hydrochlorides (4) constitute an equilibrium system involving the tautomeric forms characteristic of pseudobases 5, 6, 7 and the anhydro base 9. In aqueous solution in the pH range 7-13 the ammonium hydroxide form 5 is present. Between pH 13 and 14 the pseudobase 6 probably arises from this by covalent binding of the hydroxy group. 6 is then converted to the more stable imino type anhydrobase 9. Ring cleavage of 4 by excess alkali or of 9 by a small amount of water gives 1-(acylamidinomethylen)isoquinolines 7. Compounds 7 and 9 are stable in the solid state or in aprotic solutions but revert to cation 5 in dilute protic solutions.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230315
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  • 71
    Digitale Medien
    Digitale Medien
    [2.2](2,6)- and [2.2](2,5)Pyrazinophanes: Synthesis and Molecular Structure (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 523-533 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Hofman 1,6-elimination / Pyrazine derivatives / [2.2]Pyrazinophanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title compounds 1-3 and their methyl derivatives 4-7 were synthesized 2,11-dithia[3.3]pyrazinophanes 24-26 or by Hofmann 1,6-elimination of the appropriate [(5-methyl-2-pyrazinyl)methyl]trimethylammonium hydroxides followed by dimerization of the generated 2,5-dihydro-2,5-dimethylenepyrazines. α-Chlorination of the methylpyrazines 8-10 with N-chlorosuccinimide gave the required precursors 11, 12, 14, 17 and 18. The results of the X-ray structure determinations for 1-4 and 7 which indicate an unequivocal isomer assignment are discussed with regard to steric strain in these molecules. The electronic spectra of the pyrazinophanes 7-7 are reported and compared with those of the parent methylpyrazines.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230319
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  • 72
    Digitale Medien
    Digitale Medien
    Asymmetric Induction in the Wittig-Still Rearrangement of Ethers Containing an Allylic Stereocenter - Diastereocontrol by Allylic Nitrogen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 555-563 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Kew Words: Asymmetric induction / Alcohols, homoallylic, diastereoselective synthesis of / γ-Amino alcohols, diastereoselective synthesis of / Hydrogen bonding / [2,3] Sigmatropic rearrangement / Wittig rearrangement ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The stereochemistry of Wittig-Still rearrangements under the influence of an allylic stereogenic center attached to Bn2N or RNBoc groups is studied. Rearrangements are subject to stereocontrol through asymmetric induction. Stannylated allyl ethers 13 with Z double bonds give syn-configuration amino alcohols 15 exclusively (ds 〉95 : 〈 5 - 〉 99.8 : 〈 0.2). Stannanes of E configuration 14 lead to 15 less selectively (syn :anti = 46 : 54 - 92 : 8). X-ray structural data are provided for amino alcohol syn-15b and for the bis(carbamate) 17.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230323
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  • 73
    Digitale Medien
    Digitale Medien
    Hetero-π-Systeme, 181 Hochsubstituierte 2,4-Di-tert-butyl-1-boracyclohexadiene (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 505-511 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Borabenzene / Sandwich complex / Steric crowding ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hetero π-Systems, la. - Highly Substituted 2,4-Di-tert-butyl-l-boracyclohexadienesBoracyclohexadiees 14 and 16 with three bulky groups should be ideal starting materials for the preparation of kinetically stabilized borabenzene derivatives. They are formed by substitution reactions of anion 11, which itself is derived from 2,4-di-tert-1-methoxy-1-bora-2,5-cyclohexadiene (10) by lithiation. Reaction of lithium compound 11 with ferrous chloride provides the sandwich-type complex 12. As shown by X-ray structure analysis, 12 has C2 symmetry with the boron atoms in a syn arrangement in staggered conformation, an unusal feature for borabenzene complexes. Exchange of the methoxy group in the trimethylsilylated substance 16 leads to compounds 18a, 18b, 18c, 18d. Pyrolyses of the various precursors are described.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230317
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  • 74
    Digitale Medien
    Digitale Medien
    Synthese angularer Tetraquinane durch Photo-Thermo-Metathese diastereomerenreiner Benzochinon-Tetrahydropentalen-Addukte (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 549-554 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Metathesis, photo-thermo / Tetraquinanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis of Angularly Annulated Tetraquinanes by Photo-Thermo Metathesis of Diastereomerically Pure Adducts Between Benzoquinone and TetrahydropentalenesA retrosynthesis is presented for an angularly fused tetraquinane, the central step of which is the photo-thermo metathesis of a tetrahydropentalene - benzoquinone adduct. A sequence of Michael addition/condensation reaction gives the 3-methyl- l-phenyl-1,2-dihydropentalene (2) in 70% yield from benzalacetone and cyclopentadiene. Reaction with lithium aluminum hydride lead to a 1.0: 1.0:0.8 mixture of the 1,2,3,4-tetra-hydropentalenes 4a and 4b and the 1,2,3,5tetrahydropentalene 5. This reaction is highly diastereoselective (d.s. 〉 96%) and provides the cis compounds exclusively. Diels-Alder cycloadditon of 4a, b and 5 to benzoquinone also proceeds highly stereoselectively. The adducts 7a, b and 8 may be separated by fractional crystallization. Their relative configuration can be determined by means of 2D-COSY and NOE experiments. The endo arrangement is demonstrated by the photoreactivity of the cycloadducts. Gas-phase thermolysis (700°C/0.05 Torr) of the cage molecules 9a and 9b (from irradiation in benzene) gives the angularly annulated tetraquinanes 10a and 10b in 95 and 88% yield, respectively.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230322
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  • 75
    Digitale Medien
    Digitale Medien
    Zur Reaktion des Diphosphenyl-Komplexes (η5-C5Me5)(CO)2Fe - P=P - Aryl (Aryl = 2,4,6-tBu3C6H2) mit elektronenarmen Alkenen. Röntgenstrukturanalyse des Diphosphetans (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 733-738 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Diphosphene complexes / 1,2-Diphosphetanes ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Transition-Metal-Substituted Diphosphenes, XVIII1). - On the Reactivity of the Diphosphenyl Complex (η5-C5Me5)(CO)2Fe - P=P - Aryl (Aryl = 2,4,6-tBu3C6H2) with Electron-Deficient Alkenes. X-ray Analysis of the Diphosphetane The transition-metal-substituted diphosphene (η5-C5Me5)(CO)2Fe - P=P - Aryl (1) reacts with fumarodinitrile (2a) to give the 1,2 diphosphetane all-trans- as the result of a [2 + 2] cycloaddition. Similarly, compound 1 is converted by either dimethyl fumarate (2b) or dimethyl maleate (2c) into the same cycloadduct all-trans- (3b). Diphosphetane 3a was completely characterized by a single-crystal X-ray analysis.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230414
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  • 76
    Digitale Medien
    Digitale Medien
    Ein neuer Zugang zu enantiomerenreinen β-Lactamen aus α-Aminosäuren durch präparative Anwendung der Isonitril-Nitril-Umlagerung (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 635-638 
    Details
    ISSN: 0009-2940
    Schlagwort(e): β-Lactams / Isonitrile-nitrile rearrangement / α-Amino acids ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: A New Approach to Enantiomerically Pure β-Lactams from a-Amino Acids by Applying the Isonitrile-Nitrile Rearrangement(S)-Phenylalanine (1) was converted into (S)-3-benzyl-2-azetidinone (8b) by a multistep reaction sequence. The key step of this approach is a stereospecific isonitrile-nitrile rearrangement (3 → 4) by flash pyrolysis, which may be performed in 20-g batches of 3. An improved procedure for the preparation of (S)-Phenylalaninol (2a) is described.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230333
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  • 77
    Digitale Medien
    Digitale Medien
    Masthead (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990) 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230401
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  • 78
    Digitale Medien
    Digitale Medien
    Alkinverbrückte Vierkerncluster durch Expansion von Dreikernclustern (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 677-684 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Cluster expansion/Clusters, alkyne-bridged tetranuclear/Framework isomerism ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Alkyne-Bridged Tetranuclear Clusters by Expansion of Trinuclear ClustersUnder photochemical activation Fe2(CO)9 is a suitable reagent for the expansion of alkyne-bridged trinuclear clusters 1-7 (Fe3, FeCo2, FeNi2, RuCo2, FeCoNi, RuCoNi, RuCoMo) to the corresponding tetranuclear clusters 9-15 containing Fe(CO)3 building blocks. The analogous incorporation of RhCp building blocks was possible by heating RhCp(CO)2 together with the alkyne-bridged Fe3, FeCo2, RuCo2, RuCoMo, and RuCoW clusters 1, 2a, 4, 7, and 8. The resulting clusters 16-20 with octahedral M4C2 frameworks showed framework isomerism in two cases [RuFeCo2 (11a, b) and RuCoMoRh (19a, b)]. Crystal structure determinations were performed for the Fe4 and Fe3Rh clusters 9, 16 as well as for both isomers 19a, b of the RuCoMoRh cluster.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230405
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  • 79
    Digitale Medien
    Digitale Medien
    Wasserstoffübertragungen, 15 Zum Ablauf der Dehydrierung von Dihydroarenen durch Chinone (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 627-633 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Hydrogen transfer / Dehydrogenation of dihydroarenes / Isotope effects / Quinones, dehydrogenation with chloranile ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hydrogen Transfer Reactions, 15lI. - On the Transition State in the Dehydrogenation of Dihydroarenes by QuinonesIn the hydride abstraction from 1,2-dihydronaphthalene by o-chloroanile the regioselectivity correlates with the stability of the carbenium ions as shown by both kinetic tests and reactions of isotopomeric hydrogen donators. - The temperature dependence of primary isotope effects does not correspond with any of the categories for the transition state as proposed by Kwart2). This was examined for 1,4-cyclohexadiene and 9,10-dihydroanthracene by a Bell correction and the parameters of activation (AH/AD und [ΔEA]D/H). A VAT mechanism3) is proposed to explain both these results and the large primary isotope effects.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230332
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  • 80
    Digitale Medien
    Digitale Medien
    TiCl4/NaI - A Novel, Efficient Reagent for Mild Reduction of the N - O Bond in Amine N-Oxides and Nitrones (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 647-648 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Titanium, low-valent / Amine N-oxides / Deoxygenation ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Heteroaromatic N-oxides and nitrones were readily and selectively deoxygenated to the corresponding bases or imines in excellent yields with the TiCl4/NaI reagent system.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230336
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  • 81
    Digitale Medien
    Digitale Medien
    Optical Resolution of [2,2]Paracyclophanes by High-Performance Liquid Chromatography on Tris(3,5-dimethylphenylcarbamates) of Celllulos and Amylose (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 841-845 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Resolution, optical / Stationary phase, Chiral / Anylose carbamates / Celluslose carbamates / [3.2]Paracyclophanes, functionalized ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Optical resolution of 22 [2,2]paracyclophane derivatives was examined by high-performance liquid chromatography (HPLC) using tris(3,5-dimethylphenylcarbamates) of cellulose and amylose as chiral stationary phases. Most compounds were completely separated into enantiomers at least on one of the stationary phases. The preparation of hte new cyclophane derivatives 10, 11, 12, 14, 16, and 19 as wel as a new procedure for the synthesis of 4-fluoro-[2,2]paracyclophane (3) are described.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230432
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  • 82
    Digitale Medien
    Digitale Medien
    Pentamakrocyclische Tris-Kronen. - Selektive Bindung von Kationen, Anionen und Neutralverbindungen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 859-867 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Crown compounds / Host-guest chemistry / Macropentacyclic compounds / Phanes / Supramolecular chemistry ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Pentamacrocyclic Tris-Crown Hosts. - Selective Binding of Cationic, Anionic, and Neutral Guest CompoundsThe tris-crown host compounds 1-4 were synthesized for the first time. The X-ray crystal structures of 2 and of the 1:3 complex of 1 and KSCN were determined. Whereas in the free crown 2 a less well preorganized molecular cavity is encountered, in the complex of 1 with KSCN one potassium ion is bound to each crown ether unit. One of the three SCN- anions is situated in the interior of the cavity and in addition is disordered in such a way as to be bound to the K+ using partially the S atom of the SCN- ion. Organic guest molecules like 1,2-, 1,3-, 1,5-, 2,6-, and 2,7-naphthalenediol as well as β-naphthol in acidic water solution are bound selectively in the interior of the cavities of the host molecules 2 and 3, but not by 1 and 4, the cavities of which seem to be too small and too large, respectively. In contrast, the binding of α-naphthol and of smaller phenolic guest molecules like phenol, resorcinol, pyrocatechol, phloroglucinol, pyrogallol, and 1,2,4-trihydroxy-benzene with the host 1-4 is much less pronounced (1H- NMR highfield shifts).
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230435
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  • 83
    Digitale Medien
    Digitale Medien
    Radikalische Cyclisierung von Dienen, III Radikalische Cyclisierung von (R)-(-)-Carvon - Über den Einfluß von Charge-Transfer-Wechselwirkung auf den spezifischen Drehwert (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 901-905 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Radical-type cyclisation / Bicyclo[3.2.]octan-3-one, enantiomerically pure / Charge-transfer interactions ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Radical-Type Cyclisation of Dienes, 111. - Radical-Type Cyclisation of (R)-( - )-Carvone - On the Influence of Charge- Transfer Interactions on the Optical RotationUnder the conditions of radical cyclisation, a 1:1 diastereomeric mixture of (1R,2S,5R,R)-(+)- (2a) and (1R.2S,5R,6S)-(+)-6-methoxy-2,6-dimethylbicyclo[3.2.1]octan-3-ones (2b) is obtained from (R)-(-)-carvone in 70% yield. the configuration fo 2a and 2b were confirmed by X-ray structure analyses of their hydrazones 2d and 2e. The regio- and stereoselectivity of the radical cyclisation of 1 to 2a and 2b are discussed. The high value of the specific rotation [-555] of 2d is traced back to charge-transfer interactions between the endo-standing methoxy group at C-6 as electron donor and the dinitrophenyl-hydrazone group as electron acceptor.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230441
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  • 84
    Digitale Medien
    Digitale Medien
    Notizen / Notes Phosphorverbindungen ungewöhnlicher Koordination, 43 Hochfunktionalisierte λ3-Phosphinine aus 5,5-Dimethoxycyclopentadienen und einem kinetisch stabilisierten Phosphaalkin (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 935-937 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Key Words: Phosphaalkines / Diels-Alder reaction / λ3-Phosphinines ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Phosphorus Compounds with Unusual Coordination, 43. - Highly Functionalized λ3-Phosphinines from 5,5-Dimethoxycyclopentadienes and Kinetically Stabilized Phosphaalkyne1,2,3,4-Tetrachloro-5,5-dimethoxycyclopentadiene (5) is transformed into the λ3-phosphinine 10 by reaction with the phosphaalkyne 6; the bicyclic compound 7 is assumed to be the intermediate of the process. In an analogous way the reaction 14 + 6 yields the isomeric λ3-phosphinines 15 and 17.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230445
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  • 85
    Digitale Medien
    Digitale Medien
    “Tuning” CH/CC Bond-Activation Processes of Branched Amines by Choosing the Appropriate Gas-Phase Transition-Metal Ion (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 939-941 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Key Words: Transition-metal ions / Bond activation, CH and CC / Tandem mass spectrometry / Amines, aliphatic ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The mechanisms of the deceptively similar gas-phase chemistry of amine complexes RC(CH3)2CH2NH2/M+ (R = H, CH3 M = Fe, Co, Ni) are uncovered by the use of deuterium-labeled compounds. It is demonstrated that the details of CH/CC bond-activation reactions are strongly metal-ion-dependent, as is the product distribution itself.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230446
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  • 86
    Digitale Medien
    Digitale Medien
    Ein Cyclobutadiencarboxylat als Hetero-1,3-dien bei Diels-Alder-Reaktionen mit 2H-Azirinen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 927-933 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Cyclobutadiene / [4 + 2] Cycloaddition / 2H-Azirine / Bridgehead olefins ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Antiaromatic Compounds, 26 - A Cyclobutadienecarboxylate as a Hetero-1,3-diene in Diels-Alder Reactions with 2H-AzirinesThe cyclobutadienecarboxylic ester 1 adds 2H-azirines (2a-1) to yield the oxaazatricyclic compounds 4a-f. Under thermolysis conditions cleavage of isobutylene and formation of tricyclic ketones occurs (4a, c-e → 7a-d). The Dear pyridone 11 arises from the photolysis of 7a. The structures of compounds 4b and 11 are confirmed by X-ray crystal structure analyses.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230444
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  • 87
    Digitale Medien
    Digitale Medien
    Beiträge zur Chemie der Halogensilan-Addukte, 20. Hexakoordinierte Verbindungen von Trichlorsilanen. - Darstellung, Kristall-und Molekülstruktur von RSiCl3·bipy (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 945-951 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chlorosilanes ; hexacoordinated/Silicon complexes ; octahedral ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Hexacoordinated Compounds of Trichlorosilanes. - Preparation, Crystal and Molecular Structure of BSiCl3·bipyThe octahedral Si complexes CHCl2SiCl3·bipy (1), CCl3SiCl3·bipy (2), and Cl3SiCCl2SiCl3·bipy (3) are obtained by the reaction of the respective trichlorosilanes and 2.2′-bipyridine (bipy). Their composition is independent of the initial ratio of the components. X-ray structure determinations show the Si atoms of all three complexes to be octahedrally coordinated with the substituted methyl groups in axial positions. The configurations represent structures of least steric hindrance assuming spheric substituents and demonstrate the usefulness of this structural model for solid compounds (in contrast possibly to dissolved compounds) even for substitutents deviating strongly from this assumption. Bond lengths and angles agree with the presence of hexacoordinated complexes. Deviations from expected values are interpreted in terms of considerable steric interactions. 3 represents a case of strongly hindered coordination requiring interesting steric adjustments.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230502
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  • 88
    Digitale Medien
    Digitale Medien
    Metal Ion Binding by Amino Acids. Potassium Hydrogen L-Glutamate Monohydrate K(L-GluH)·H2O (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1001-1004 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Amino acid complexes ; L-Glutamate complexes ; Hydrogen L-glutamate complexes ; Potassium hydrogen L-glutamate ; Hydrogen bonding ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The title compound is obtained by neutralization of aqueous solutions of L-glutamic acid with potassium hydroxide, and crystallization from aqueous methanol. The compound shows a pH of 7 in water at ambient temperature and an optical rotation [α]20D of -4.30 (c = 3.0). In the crystal (orthorhombic, space group P212121) the potassium ion is in a distorted trigonal-prismatic environment of six oxygen atoms of four different amino acids and of the water molecule. No nitrogen coordination is observed. Through the bridging function of some of the α-carboxylate oxygen atoms (O1, O2) and through complexation of the metal through the γ-carboxylate groups (O3), a layer-coordination polymer, with strings of potassium ions running parallel, is formed. The layers are cross-linked by hydrogen bonds involving the ammonium and γ-carboxylate functions as well as the water molecule.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230512
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  • 89
    Digitale Medien
    Digitale Medien
    Darstellung, Struktur und Stereoisomerie von 1,3-Di-tert-butyl-1,3,2,4-diazadistibetidinen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 975-978 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 1,3,2,4-Diazadistibetidines, 1,3-di-tert-butyl- ; Geometrical isomers ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis, Structure, and Stereoisomerism of 1,3-Di-tert-butyl-l,3,2,4-diazadistibetidinesStarting from 1,3-di-tert-butyl-2,4-dichloro-1,3,2,4-diazadistibetidine a series of 1,3,2,4-diazadistibetidines [R-SbN-ttBu]2 with R = OMe (2), OPh (3), OtBu (4), N(Tms)2 (5), P(Tms)2 (6), Me (7), and tBu (8) has been synthesized. The NMR spectra prove most of the reaction products to be mixtures of geometrical isomers. The structure of trans-tetra-tert-butyldiaza-distibetidine 8a was confirmed by X-ray structure determination.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230507
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  • 90
    Digitale Medien
    Digitale Medien
    Synthese und Reaktionen von 2-Pyridylphosphan, 2-C5NH4-PH2 (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 989-993 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphane ; 2-pyridyl- ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and Reactions of 2-Pyridylphosphane, 2—C5NH4-PH2By reduction of diethyl 2-pyridylphosphonate (1) with LiAlH4 2-pyridylphosphane (2) is accessible in ≍80% yield. H/D exchange experiments and acid/base exchange reactions between 2 and PhPHLi or Ph2PLi show (2) to be a stronger pH acid than PhPH2 and Ph2PH. Silylation of the lithium phosphides 2-C5NH4-PRLi (R — H, SiMe3) with Me3SiCl affords the corresponding silyl derivatives 2-C5NH4-PR2 with CH3I or CH2Cl2 yields the mono- or bidentate secondary phosphanes 2-C5NH4-PHMe (6) and 2-C5NH4PHCH2PH-2-C5H4N (5), respectively. On treatment of 2 with CH3I or HCl the pyridinium salts [(2-C5NH4R)PH2]+X- (R — H, Me; X= Cl, I) are formed. However, coordination of 2 to transition metals in low oxidation states occurs by the phosphorus atom. Addition of the PH bonds in 2 to the activated C—C double bonds in acrylic acid esters, mesityl oxide, cinnamnic acid esters, and dimethyl vinylphosphonate leads to chiral P,N hybrid ligands with functional groups in the alkyl side chain.
    Zusätzliches Material: 3 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230510
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  • 91
    Digitale Medien
    Digitale Medien
    Präorganisierte Bis-ethine: Molekulare π-Pinzetten? (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1097-1103 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Bond formation, C-C ; Iron complexes ; Macrocycles ; Molecular tweezers ; Naphthalenophane ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Preorganized Bis-ethynes: Molecular π-Tweezers?1,8-Bis[(arylethynylphenyl)]naphthalenes of type V (e.g. 10, 11) and 1,8-bis[(arylethenylphenyl)]naphthalenes (6, 6a, 7, 7a) were synthesized for the first time. In contrast to the known 1,8-bis(arylethynyl)naphthalenes VI their “stereologs” 10 and 11 are thermally stabile. Yet they react with pentacarbonyliron to yield dinuclear transition metal complexes of the type 12, 13, i.e. a strained cyclophane macrocycle is formed by C-C bond formation. The X-ray analysis of the di-tert-butyl compound 11 shows that the peri substituents diverge, but with increasing distance from the naphthalene skeleton one of the arylethynyl units is bent to the opposite direction (Figure 2). The question whether the new molecular skeleton V can be viewed as molecular tweezers is discussed: as the hydrocarbons react irreversibly with transition metal carbonyls, they may rather be taken as “tweezers for single use”.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230524
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  • 92
    Digitale Medien
    Digitale Medien
    Synthese und Eigenschaften kalamitischer Flüssigkristalle aus desoxygenierten Kohlenhydrat-Derivaten (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1129-1135 
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    ISSN: 0009-2940
    Schlagwort(e): Deoxy sugars ; Glycosyl cyanides ; Liquid crystals, chiral, thermotropic ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Synthesis and Properties of Calamitic Liquid Crystals from Deoxygenated Carbohydrate DerivativesTreatment of the L-arabino- and Llyxo-configurated glycals 1 and 7 with trimethylsily cyanide leads to the formation of the anomeric nitriles 2, 3 and 15, 17, respectively. The configurational assignments are based on hydrogenated products such as 6 or 8 and 10. Depending on the configurations of the olefinic nitril sugars, various hydrogenation results are observed using palladium/charcoal or the Wilkinson catalyst. Methanolysis provides the corresponding methyl esters. The preparation of liquid-crystalline derivatives follows the classical route. In comparing the properties of these saccharide-based liquid crystals with the corresponding cyclohexane derivatives, the dominant influence of the anomeric effect on the tendency for phase formation can be observed. Some of the novel derivatives show highly twisted cholesteric and wide blue phases.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230528
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  • 93
    Digitale Medien
    Digitale Medien
    Photochemical Dehydrogenation, Ring Contraction, and Ring Expansion of Hydrogenated Derivatives of Benzoxazino-benzoxazine, Quinoxalino-quinoxaline, and Bibenzothiazole (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1149-1154 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Photochemistry ; Benzoxazino-benzoxazines ; Quinoxalino-quinoxalines ; Bibenzothiazoles ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The photochemical properties of the title compounds have been investigated and compared. The benzoxazino-benzoxazine derivatives 1 are photochemically converted into hydrogenated oxazole derivatives. In some cases this ring contraction is accompanied by a dehydrogenation reaction whereby the heterocyclic ring system becomes aromatic. Hydrogenated quinoxalino-quinoxalines also undergo a photodehydrogenation reaction and become aromatic. However, a ring contraction yielding the imidazolyl system does not take place. The only investigated sulfur-containing analog has different properties. The stable form is the bibenzothiazole 23 which contains a five-membered heterocyclic ring system. Photochemically 23 rearranges under ring expansion to give the benzothiazino-benzothiazine 24.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230531
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  • 94
    Digitale Medien
    Digitale Medien
    9,10-Phenanthrenocyaninatoeisen(II) (PhcFe) und axial koordinierte Isocyanid-Komplexe (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1105-1110 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 9,10-Phenanthrenocyaninatoiron(II) ; Isocyanide complexes ; Porphyrin derivatives ; Semiconductors, organic ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: 9,10-Phenanthrenocyaninatoiron(II) (PhcFe) and Axially Coordinated Isocyanide Complexes9,10-Phenanthrenocyaninatoiron(II) (PhcFe) is synthesized from 9,10-dicyanophenanthrene (3) and pentacarbonyliron. PhcFe exhibits similar spectroscopic properties (UV/VIS and Mößbauer spectra) and similar oxidation potentials as 1,2-Naphthalocyaninatoiron(II) (1,2-NcFe) and Phthalocyaninatoiron(II) (PcFe). Isocyanides RNC (R = tBu, cHx, Bzl, Me2Ph) react with PhcFe to form the corresponding bisaxially substituted 9,10-phenanthrenocyaninatoiron(II) compounds 4-7. Reaction of PhcFe with 1,4-diisocyanobenzene (dib) yields the bridged complex [PhcFe(dib)]n.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230525
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  • 95
    Digitale Medien
    Digitale Medien
    (E,Z) Equilibria, 12. Differential NMR Shielding by Phenyl, Assigned from Chemical Labelling and (Z,E) Equilibration (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1137-1141 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Allyl anion ; Differential NMR-shielding ; Schiff's bases ; Stereoselective substitution ; Isomerization, (Z,E) ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Unequivocal NMR assignments of the (E,Z) isomeric pairs 3 and 8 are possible by (Z,E) equilibration. Deprotonation of 2-methyl-1-phenylpropene (1) with n-BuLi under any conditions gives only a single allyl-metal derivative 2. Methylation of the latter gives the isomer (Z)-3, while deuteriolysis leads to the isotopically labelled derivative 6 of the olefin 1; this Proves the NMR assignments for 1 as well as the endo configuration of 2. The phenyl group gives rise to a differential shielding effect on the γ-carbon nuclei in methyl and methylene gropus along a CC double bond (ca, 7 ppm), and this effect is comparable to that along a CN double bond as in 8. The nitrile function in 5c is much less effective.
    Zusätzliches Material: 1 Tab.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230529
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  • 96
    Digitale Medien
    Digitale Medien
    Künstliche molekulare Anion-Wirte. Die Synthese eines chiralen bicyclischen Guanidinium-Salzes als funktionalisierte Ankergruppe für Oxo-Anionen (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 907-915 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Molecular recognition / Anion host compound / Guanidmiun salt / Chiral synthesis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Artificial Molecular Anion Hosts. Synthesis of a Chiral Bicyclic Guanidinium Salt Serving as a Functionalized Anchor Group for 0x0 AnionsStarting from 1-asparagine, the synthesis of the S,S-bis(hydroxymethyl)-substituted bicyclic guanidinium salt 3 is described, which is obtained in 20% overall yield with a diastereomeric excess de 〉 98%. The guanidinium compound 3 may serve as a binding module in the enantioselective recognition of oxo anions in polytopic abiotic receptors.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230442
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  • 97
    Digitale Medien
    Digitale Medien
    Masthead (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990) 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230501
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  • 98
    Digitale Medien
    Digitale Medien
    Diphosphinonitrenium and -phosphenium Cations, Jahn-Teller Distorted Allyl Systems (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 971-973 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Calculations ; Jahn-Teller distortion ; Nitrenium ; Phosphenium ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Ab initio calculations at SCF, MCSCF, and ACPF level were performed on a series of the phosphenium- and nitreniumcation family. These show that they possess an allylic π-system with 4 electrons, which is distorted from planarity when the terminal groups of the allylic system are PR2 (R — H) fragments. The distortion is such as to adopt C2 symmetry, and is the consequence of Jahn-Teller distortion via mixing of the energy highest π2 orbital with an energetically low lying δ* orbital. The latter interaction is only operative if a symmetry breaking from C2v to C2 symmetry occurs. The importance of Jahn-Teller distortion on the biradical character in these systems is investigated by correlation calculations.
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230506
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  • 99
    Digitale Medien
    Digitale Medien
    Lineare Oligophosphaalkane, XXV. Synthese von Ph2P—CH2—PH2 und (ph2P—CH2)2PH durch Phosphinomethylierung von PH3 unter Phasentransferkatalyse (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 995-999 
    Details
    ISSN: 0009-2940
    Schlagwort(e): Phosphine ; Phosphinomethylation ; Phase-transfer catalysis ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Linear Oligophosphaalkanes, XXV1. - Synthesis of Ph2P—CH2—PH2 and (Ph2P—CH2)2PH by Phosphinomethylation of PH3 with Phase-Transfer CatalysisAlkylation of Ph2PH with CH2Cl2 under phase-transfer conditions in the system dichloromethane/toluene/water affords Ph2P-CH2Cl in high yields. Depending on the reaction conditions employed Ph2P-CH2Cl reacts with PH3 in the two phase system under phase-transfer catalysis (nBu4NCl) to yield the tertiary-primary methylenebis(phosphane) Ph2P-CH2-Ph2 (2) or the PH functional triphosphaalkane Ph2P-CH2-PH-CH2-PPh2 (3), respectively. Metallation of 2 and 3 with RLi (R = nBu, tBu) and subsequent reaction with Me3siCl yields the silyl derivatives 2e and 3b, respectively. The analysis of the 1H- 13C- and 31P-NMR spectra is reported.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230511
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  • 100
    Digitale Medien
    Digitale Medien
    Organosubstituierte 1,6-Dioxa-2-sila-5-bora-3-cycloalkene - Herstellung und Charakterisierung (1990)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 123 (1990), S. 1013-1028 
    Details
    ISSN: 0009-2940
    Schlagwort(e): 1,2,5-Azasilaboroles, organo-2,5-dihydro- ; Dihydroxyalkanes(arenes) ; 1,6-Dioxa-2-sila-5-bora-3-cycloalkenes ; Regio- and stereoisomers ; Metathesis, BO ; Chemistry ; Inorganic Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Organosubstituted 1,6-Dioxa-2-sila-5-bora-3-cycloalkenes - Preparation and Characterisation1)The cis-alkenes ROSi(CH3)2C(R) = C(C2H5)B(C2H5)OR (R = CH3: 11; C2H5: 12; C6H5: 13) are prepared from CH3NSI[CH3)2C(R)=C(C2H5)BC2H5 [R = CH3: A; R = C(CH3) = CH2: B] with the monohydroxy compounds ROH (R = CH3, C2H5, C6H5). A or B react with aliphatic dihydroxy compounds HO—R′—OH [R′ = —CH2CH2—: 1; —CH(CH3)CH2—: 2; —CH(CH3)—CH(CH3)—: 3; —C(CH3)2C(CH3)2—: 4; —(CH2)3: 5; —(CH2)4—: 6] to give 8-, 9-, and 10-membered ring compounds OSi(CH3)2C(R) = C(C2H5)OR′ [15a,b, 16/16′, meso/rac-17a, D-17a,b, 18, 19, (20)n]. A is initially cleaved at the SiN bond with formation of 14 Compound 15a crystallises as the 16-membered (15a)2 [X-ray structure analysis). The aromatic dihydroxy compounds catechol (7), resorcinol (8), 2,3-dihydroxynaphthalene (9), 1, 8-dihydroxynaphthalene (10) react with A to form 21 to 24, but mainly by protolytic BCvinyl fission to give the 2,5-dihydro-1,2,3-dioxaboroles (e.g. 7f1, 9f1, 10f1) and the acyclic boron-free compounds 7f′3, 9f3, 10f3. The MS and NMR (1H, 11B, 13C, 29Si) data of the new compounds are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/cber.19901230514
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