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  • 1
    Electronic Resource
    Electronic Resource
    Progress towards a generalized solvent polarity scale: The solvatochromism of 2-(dimethylamino)-7-nitrofluorene and its homomorph 2-fluoro-7-nitrofluorene (1995)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1995 (1995), S. 241-252 
    Details
    ISSN: 0947-3440
    Keywords: Polarity scale ; Solvatochromism ; Solvent polarity scale ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: More than 100 solvents and the gas phase were used to develop a solvent dipolarity-polarizability scale that combines the medium dipolarity and polarizability into a single parameter (SPP) calculated from the UV-visible spectra of 2-(dimethyl-amino)-7-nitrofluorene (DMANF) and its homomorph 2-fluoro-7-nitrofuorene (FNF). The proposed scale compares favourably for nonprotic solvents with existing solvent polarity scales including Kosower's Z, Dimroth and Reichardt's ET(30), Brooker's χR, Dong and Winnick's Py; Kamlet, Abboud, and Taft's π*, and Drago's S′ scale. When data are derived from electronic transitions, they provide an accurate description for the solvent effect in UV-Vis, IR, NMR, and fluorescence spectroscopy as well as in other chemical areas including thermodynamics and kinetics.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199519950234
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A Generalized Solvent Basicity Scale: The Solvatochromism of 5-Nitroindoline and Its Homomorph 1-Methyl-5-nitroindoline (1996)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1996 (1996), S. 1785-1794 
    Details
    ISSN: 0947-3440
    Keywords: Solvent basicity scale ; Solvent effects ; Solvatochromism ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A total of 202 organic solvents and the gas phase were placed on a solvent basicity scale for hydrogen bond acceptor based on parameter SB. The value of such a parameter can readily be determined from the UV/Vis spectrum for an appropriate acid probe (5-nitroindoline) (NI) and its non-acid homomorph (1-methyl-5-nitroindoline) (MNI). The proposed scale can advantageously substitute the more widely used solvent scales such as Gutmann's donor number (DN), the Koppel-Palm B(MeOD) scale, and the Taft-Kamlet β scale. While data for the proposed scale are derived only from electronic transitions, they are accurately descriptive of solvent basicity in both spectroscopy (UV/Vis, IR and NMR) and miscellaneous chemical areas (thermodynamic, kinetics, and electrochemistry).
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199619961112
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  • 3
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    Antarctic ozone - Meteoric control of HNO3 (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Atmospheric circulation leads to an accumulation of debris from meteors in the Antarctic stratosphere at the beginning of austral spring. The major component of meteoric material is alkaline, comprised predominantly of the oxides of magnesium and iron. These metals may neutralize the natural acidity of stratospheric aerosols, remove nitric acid from the gas phase, and bond it as metal nitrates in the aerosol phase. Removal of nitric acid vapor has been previously shown to be a critical link in the photochemical depletion of ozone in the Antarctic spring, by allowing for increased catalytic loss from chlorine and bromine.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 15; 1-4
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  • 4
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    The role of chlorine chemistry in Antarctic ozone loss - Implications of new kinetic data (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: New kinetic data yielding a slower formation rate and larger absorption cross sections of Cl2O2 are incorporated into a photochemical model to reassess the role of chlorine chemistry in accounting for the ozone reductions derived from TOMS observations in different regions of the Antarctic polar vortex during 1987. The model is further constrained by existing measurements from the Airborne Antarctic Ozone Experiment and the National Ozone Expedition II. Calculated concentrations of ClO based on the new kinetic data increase by almost a factor of two between the collar and core regions of the vortex during the second half of September. The calculated ozone reductions in the vortex core appear to be consistent with the TOMS observations in spite of the slower rate for the self-reaction of ClO.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 17; 255-258
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  • 5
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    Impact of biomass burning on tropospheric CO and OH - A two-dimensional study (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Results are presented from a 2D model of the troposphere and stratosphere which allows the derivation of a budget for CO, as well as the assessment of contributions from different sources in maintaining observed CO concentrations. Attention is given to the results of a time-dependent calculation which evaluates the impact of present-day biomass burning on CO, OH, and CH4, as well as the time constants for the system to respond to changes in the biomass source.
    Keywords: GEOPHYSICS
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  • 6
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    Chlorine chemistry in the Antarctic stratosphere - Impact of OClO and Cl2O2 and implications for observations (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Theories have been proposed to relate the reduction of O3 during Antarctic spring to catalytic cycles involving chlorine and bromine species. A necessary condition for any chlorine-catalyzed scheme is that a large fraction of the chlorine must be in the form of ClO in the lower stratosphere. It has been suggested that these high levels of ClO could be maintained by fast heterogeneous reactions, whose rates are not known at present. Model calculations based on the above mechanisms predict considerable amounts of OClO and Cl2O2, particularly during the night. Results of calculations of the diurnal variations of ClO, OClO, and Cl2O2 during Antarctic spring are presented for different cases. Results from the calculations suggest that coincident measurements of the total column abundance and diurnal variation of ClO and OClO may help constrain key aspects of the proposed chemical mechanisms. Removal of O3 by the catalytic cycle involving Cl2O2 could be as important as that involving BrO for present levels of chlorine, provided that Cl2O2 photolyzes rapidly to yield Cl and ClO2. It is shown that there is no synergy between these two cycles, since they both compete for the available ClO.
    Keywords: GEOPHYSICS
    Type: (ISSN 0094-8276); 13; 1292-129
    Format: text
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  • 7
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    Antarctic chlorine chemistry - Possible global implications (1988)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: Occurrence of heterogeneous reactions on the surface of polar stratospheric clouds (PSC) is a necessary component of the Cl-related chemical mechanisms proposed to explain the recently observed decrease of O3 during Antarctic spring. A one-dimensional model is used to assess the impact of these heterogeneous reactions on future global O3 trends if they were to occur on the global aerosol layer. The impact of these reactions on the concentration of Cl species in the present-day atmosphere is also calculated. The reaction (ClNO3 + HCl) could have a large impact on stratospheric O3. A fast rate for this reaction would greatly enhance the present concentration of ClO and reduce the abundance of HCl in the lower stratosphere. Because of the large differences between the Antarctic and global environments, the calculated global O3 trends are smaller than those calculated for Antarctica.
    Keywords: GEOPHYSICS
    Type: Geophysical Research Letters (ISSN 0094-8276); 15; 257-260
    Format: text
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