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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2408-2417 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: AcenazulenedionesReactions of 8-methoxyheptafulvene (1) and quinones 2 give in [8+2]-cycloadditions hydroacenazulenediones 3, which are immediately transformed to acenazulenediones 4 and 5. The yields in the reaction sequence depend on the half-wave-reduction-potentials (E1/2) of 2. Only compounds 2 with E1/2 (in acetonitrile, vs s.c.e.) lower than - 0.5 V lead to cycloadducts in reasonable yields. Properties of the ground and excited states of 4 and 5 are characterized by spectroscopic methods and molecular-orbital-calculations.
    Notes: Die Titelverbindungen 4 und 5 werden über [8+2]-Cycloadditionen aus 8-Methoxyheptafulven (1) und den Chinonen 2 dargestellt. Die Ausbeuten an 4 und 5 hängen von den Halbstufen-Reduktionspotentialen (E1/2) der Chinone 2 ab. Die Cycloadditionen werden nur bei Chinonen mit E1/2 〈 -0.5 V (in CH3CN, vs SCE) beobachtet; stärker oxidierende Chinone führen zur Polymerisation von 1. Die Grundzustandseigenschaften und Eigenschaften der angeregten Zustände von 4 und 5 werden durch spektroskopische Methoden und Berechnungen charakterisiert.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 2643-2651 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Formation of Complexes and Electron Transfer Reactions of 8,8-Bis(dimethylamino)heptafulvene, Reactions with Nonacarbonyldiiron and TetracyanoquinodimethaneThe synthesis of 8,8-bis(dimethylamino)heptafulvene (2) ist described. Reaction of nonacarbonyldiiron (8) with 2 leads to the tricarbonyl(heptafulvene)iron complex 9 which is fluxional on the NMR time scale. One electron transfer occurs during the reaction of 2 and tetracyanoquinodimethane (5) forming 2+. and 5-. 2+. dimerizes to bicycloheptatrienylmethyl cation. Depending on the reaction conditions 5-. forms a complex with 5 or is reduced to 52-.
    Notes: Die Synthese von 8,8-Bis(dimethylamino)heptafulven (2) ist beschrieben. Durch die Umsetzung von 2 mit Nonacarbonyldieisen (8) entsteht der Tricarbonyl(heptafulven)eisen(0)-Komplex 9. Dieser fluktuiert in der NMR-Zeitskala. Eine Einelektronentransfer-Reaktion erfolgt zwischen 2 und Tetracyanchinodimethan (5) unter Bildung von 2+. und 5-. 2+. stabilisiert sich durch Dimerisierung. 5-. wird je nach Reaktionsbedingungen an 5 assoziiert oder reduziert zum Dianion 52-.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1154-1173 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Fulvenes with Inverse Ring Polarization, 10. Electron Rich HeptafulvenesThe synthesis and structural properties of the electron rich heptafulvenes 3a - f are described. The compounds 3 have electron donor substituents at C-8. In the case of 3f NMR-spectroscopy revealed the presence of a boat conformation with bond alternation. HMO-calculations showed that, depending on the electron donor properties, the C-8 substituents lead to a characteristic “HOMO-LUMO-GAP-NARROWING”.  -  The new compounds 3a - f have been synthesized either from derivatives of 1,3,5-cycloheptatriene-7-carboxaldehyde or from cycloheptatriene-7-carboxylic acid.
    Notes: Synthesen und Struktureigenschaften der elektronenreichen Heptafulvene 3a - f werden beschrieben. Die Verbindungen 3 haben Donorsubstituenten an C-8. Am Beispiel des Bis(dimethylamino)heptafulvens 3f wurde mit 1H-NMR gezeigt, daß die Bootkonformation vorliegt und die C — C-Bindungen Bindungsalternanz zeigen. Zur weiteren Charakterisierung des π-Systems wurde das HMO-Modell verwendet: Charakteristisch ist insbesondere die Verringerung der Energielücke zwischen den Grenzorbitalen durch die Donorsubstituenten an C-8  -  Die Verbindungen 3a - f wurden entweder aus Derivaten des 1,3,5-Cycloheptatrien-7-carboxaldehyds oder der Cycloheptatrien-7-carbonsäure synthetisiert.
    Additional Material: 6 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1777-1786 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cross Conjugated Enolates: Structure Characterization of Two Lithium HeptafulvenolatesWhen deprotonated, N,N-dimethylcycloheptatriene-7-carboxamide (2a) and cycloheptatriene-7-carboxylic acid (2c) yield the amide anion 4a and the acid dianion 4c. Due to the NMR spectra, 4a and c show in the range 600-700 nm three and two signals, respectively. The spectra are temperature and solvent dependent. The THF-solution of 4c is paramagnetic. The structures of the organolithium compounds are discussed.
    Notes: Die bei der Deprotonierung von N,N-Dimethylcycloheptatrien-7-carboxamid (2a) und Cycloheptatrien-7-carbonsäure (2c) entstehende Lithiumverbindung 4a und Dilithiumverbindung 4c werden spektroskopisch charakterisiert. 4a und c sind Heptafulvene, d. h. das Lithium ist am Sauerstoff lokalisiert. Die Elektronenspektren von 4a und c im Bereich 600-700 nm zeigen drei bzw. zwei Banden, deren Intensitäten von der Lösungsmittelzusammensetzung und der Temperatur abhängen. Die Lösung von 4c in Tetrahydrofuran ist paramagnetisch. Die Strukturen der lihiumorganischen Verbindungen werden diskutiert.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 99-118 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cycloheptatrienes and Norcaradienes1): Relation between Hindrance of Rotation about the C-7-C-8 Bond and StructureIn order to elucidate factors responsible for substituent effects on cycloheptatriene-norcaradiene equilibria, the imidazolidinylium compound 12a and b, and the spiro molecules 13a and b are investigated. The synthesis of 12a starts from 7-cyanocycloheptatriene (14). Bisalkylation of dilithium heptafulvenediolate 17 affords 13. Compounds 12 and 13 are characterized by cycloadditions (→ 15, 22). Concerning the equilibrium 12a ⇌ 12b no norcaradiene could be traced by NMR. At room temperature 13a and b form a fast and dynamic equilibrium with [13a]:[13b] = 42:58. Thermodynamic parameters are given. The crystal structures of the compounds were determined by X-ray analysis. Both compounds are cycloheptatrienes with boat stereochemistry. The carbonyl group in 13a is exo, the cation substiuent in 12a is endo.
    Notes: Cycloheptatrien-7-ylimidazolidin-2-ylium-tetrafluoroborat (12a) wurde aus 7-Cyancycloheptatrien (14) und Aziridinium-tetrafluoroborat synthetisiert. Spirocycloheptatrien 13a und Norcaradien 13b entstehen durch cyclisierende Alkylierung des Dilithium-heptafulvendiolats 17. Mit Dienophilen bilden 12 und 13 die Polycyclen 15 und 22. NMR-Untersuchungen schließen einen nennenswerten Anteil von Norcaradien 12b im Gleichgewicht mit 12a aus. Dagegen stehen bei 284 K Cycloheptatrien 13a und Norcaradien 13b mit 42:58 im Gleichgewicht [ΔΔH0(NCD—CHT) = -1 kcal/mol, ΔΔS0(NCD—CHT) = -3 cal/Grad. mol]. Nach der Röntgenstrukturanalyse liegt 12a im Kristall in der Bootform mit endo-ständigem 7-Substituenten vor; von 13a ⇌ 13b ist im Kristall nur die Cycloheptatrienstruktur 13a mit exo-ständiger Carbonylgruppe stabil.
    Additional Material: 8 Ill.
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  • 6
    Publication Date: 2019-06-28
    Description: Improved knowledge of the Earth's gravity field was obtained from new and improved satellite measurements such as satellite to satellite tracking and gradiometry. This improvement was examined by estimating the accuracy of the determination of mean anomalies and mean undulations in various size blocks based on an assumed mission. In this report the accuracy is considered through a commission error due to measurement noise propagation and a truncation error due to unobservable higher degree terms in the geopotential. To do this the spectrum of the measurement was related to the spectrum of the disturbing potential of the Earth's gravity field. Equations were derived for a low-low (radial or horizontal separation) mission and a gradiometer mission. For a low-low mission of six month's duration, at an altitude of 160 km, with a data noise of plus or minus 1 micrometers sec for a four second integration time, we would expect to determine 1 deg x 1 deg mean anomalies to an accuracy of plus or minus 2.3 mgals and 1 deg x 1 deg mean geoid undulations to plus or minus 4.3 cm. A very fast Fortran program is available to study various mission configurations and block sizes.
    Keywords: GEOPHYSICS
    Type: REPT-307
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  • 7
    Publication Date: 2019-06-27
    Description: Geoids computed from GEOS-3 altimeter data are compared with gravimetric geoids computed by various techniques for 30 x 30 deg areas in the Tonga Trench and the Indian Ocean. The gravimetric geoids were calculated using the standard Stokes integration with the Molodenskii truncation procedure, the modified Stokes integration suggested by Ostach (1970) and Meissl (1971) with modified Molodenskii truncation functions, and three sets of potential coefficients including one complete to degree 180. It is found that the modified Stokes procedure with a cap size of 10 deg provides better results when used with a combined altimeter terrestrial anomaly field data set. Excellent agreement at the plus or minus 1 m level is obtained between the altimeter and gravimetric geoid using the combined data set, with the modified Stokes procedure having a greater accuracy. Coefficients derived from the 180 x 180 solution are found to be of an accuracy comparable to that of the modified Stokes method, however to require six times less computational effort.
    Keywords: GEOPHYSICS
    Type: Bulletin Geodesique; 54; 2, 19; 1980
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  • 8
    Publication Date: 2019-06-28
    Description: Ellipsoidal correction terms have been derived for geoid undulation computations when the Stokes equation using gravity anomalies in a cap is combined with potential coefficient information. The correction terms are long wavelength and depend on the cap size in which its gravity anomalies are given. Using the regular Stokes equation, the maximum correction for a cap size of 20 deg is -33 cm, which reduces to -27 cm when the Stokes function is modified by subtracting the value of the Stokes function at the cap radius. Ellipsoidal correction terms were also derived for the well-known Marsh/Chang geoids. When no gravity was used, the correction could reach 101 cm, while for a cap size of 20 deg the maximum correction was -45 cm. Global correction maps are given for a number of different cases. For work requiring accurate geoid computations these correction terms should be applied.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research; 86; Nov. 10
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  • 9
    Publication Date: 2019-06-28
    Description: The computation of accurate geoid undulations is usually done combining potential coefficient information and terrestrial gravity data in a cap surrounding the computation point. In doing this a spherical approximation is made that can cause the errors that were investigated. The equations dealing with ellipsoidal corrections developed by Lelgemann and by Moritz were used to develop a computational procedure considering the ellipsoid as a reference surface. Terms in the resulting expression for the geoid undulation are identified as ellipsoidal correction terms. These equations were developed for the case where the Stokes function is used, and for the case where the modified Stokes function is used. For a cap of 20 deg the correction can reach -33 cm.
    Keywords: GEOPHYSICS
    Type: NASA-CR-164440 , REPT-308
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  • 10
    Publication Date: 2019-06-28
    Description: Geoid undulations derived from Doppler satellite positioning are compared with corresponding values derived from terrestrial and satellite information using three different procedures. Doppler undulations are compared with uncorrected gravimetric undulations, and systematic differences of 1.6 m and 0.4 m are found for western and eastern U.S. stations, respectively. The systematic difference of 1.6 m was reduced to 0.1 m when terrain-related corrections were applied. Undulations computed from a spherical harmonic expansion to degree 180 yielded standard deviations only slightly poorer than the combined data. A more systematic difference in the western than in the eastern stations remained.
    Keywords: GEOPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 89; 1105-111
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