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  • 1
    Electronic Resource
    Electronic Resource
    Calorimetric study of the anomeric effect in 2-carboethoxy-1,3-dithianes (1994)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 7 (1994), S. 561-566 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpic contribution to the anomeric effect in r-2-carboethoxy-trans-4,trans-6- and r-2-carboethoxy-cis-4,cis-6-dimethyl-1,3-dithianes was determined by reaction-solution calorimetry. The enthalpy of solution of both isomers in pure p-dioxane and the enthalpy of solution and isomerization in the same solvent and in the presence of trifluoroacetic acid were experimentally measured. From these results the corresponding enthalpies of isomerization in solution were calculated, and were found to be ΔHax→eq = -0·16 ± 0·04 kcal mol-1 (-0·67 ± 0·18 kJ mol-1) and ΔSax→eq = -2·68 ± 0·1 cal K-1 mol-1 (-11·2 ± 0·4 J K-1 mol-1). The slightly negative ΔH term nevertheless reflects a substantial anomeric effect owing to the countervailing steric effects in the axial isomer. The significant entropy loss in the equatorial isomer was explained in terms of intramolecular electrostatic effects. The results are in agreement with those obtained from NMR studies of the conformational behaviour of 2-carboethoxy-5-methyl-5-aza-1,3-dithiacyclohexane.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610071007
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  • 2
    Electronic Resource
    Electronic Resource
    Brønsted coefficients and the theory of acid-base catalysis of proton transfers from carbon acids (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 95-109 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The intersecting-state model previously used to interpret proton transfers in ground and excited states and enzyme catalysis was applied to the general acid-base catalysis of carbon acids. The results are consistent with the predictions published for these systems and provide a new physical meaning for the Brønsted coefficients. It is shown that in addition to the linear free energy effect, the Brønsted coefficients are also influenced by the tightness of the transition states and by electronic effects. The model suggests that the increased reactivity of carbon acids towards proton transfer in non-hydrogen-bonding solvents is caused by an added electronic effect on the thermodynamics of the reactions. The curvatures of the Brønsted plots are interpreted in terms of an entropic contribution to the position of the transition state.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030206
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  • 3
    Electronic Resource
    Electronic Resource
    Structure of 1,2,6-thiadiazine 1,1-dioxides (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 470-476 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio theoretical calculations were carried out on the three tautomers, NH, OH and CH, of 1,2,6-thiadiazine 1,1-dioxides. Different basis sets were employed in order to obtain an adequate description of these cyclic sulphamide derivatives. A coherent picture is obtained which includes relative stability of tautomers (NH 〉 CH 〉 OH), non-planarity of NH and CH tautomers and electronic distribution (Boys' localized orbitals).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030709
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  • 4
    Electronic Resource
    Electronic Resource
    Binding of lithium ion isotopes with redox-active macrocyclic and macrobicyclic crown ethers (1992)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 5 (1992), S. 711-714 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Three anthraquinone-containing crown ether macrocycles and one macrobicycle were reduced coulometrically to their corresponding anion radicals under vacuum. The resulting anion radical solutions in CH2CL2 were stirred with an excess of a solid 6LiClO4-7LiClO4 mixture of known isotropic composition in order to form the appropriate Li+ complexes. After equilibration, the solution was separated from the excess solid and the [6Li+]/[7Li+] ratio was determined by atomic absorption spectrometry. The values were converted into the corresponding separation factors (α) after division by the original composition ratio of the solid mixture. The values were in the range 1.04-1.18. Except for one compound, 2, all of the reduced systems studied exhibited a much larger α value than the 1.057 reported for 12. crown-4 at 0° C in a liquid-liquid extraction system.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610051013
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  • 5
    Electronic Resource
    Electronic Resource
    AB initio MO study of the halogen cation basicities of some organic bases (1991)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 4 (1991), S. 177-191 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Hartree - Fock calculations were performed to investigate the structure and relative stabilities of complexes between halogen cations and first- and second-row bases. It is shown by means of both a qualitative perturbation molecular orbital treatment and a topological analysis of the electronic charge density that second-row bases present enhanced halogen cation basicities compared with first-row bases. In this respect the results predict that although the fluorine cation basicity of water is smaller than its proton affinity, the fluorine cation basicities of SH2, thioether, phosphine and trimethylphosphine are considerably higher than their proton basicities. Similarly, phosphine and trimethylphosphine should have chlorine cation basicities greater than their proton affinities, in contrast with ammonia and trimethylamine. The results also show that fluorine and chlorine cation basicities are more sensitive to methyl substitution than proton affinities.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610040309
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  • 6
    Electronic Resource
    Electronic Resource
    Letters to the editor (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 635-640 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380421
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  • 7
    Electronic Resource
    Electronic Resource
    Gas-liquid mass transfer in stirred tanks (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1768-1772 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690361121
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  • 8
    Electronic Resource
    Electronic Resource
    Estimation of surface tension of pure fluids using the gradient theory (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 753-760 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The modified van der Waals theory of interfaces (gradient theory) is used with the equations of state of Peng-Robinson and Mohanty-Davis to predict surface tensions of various nonpolar, quadrupolar, slightly polar and polar substances as a function of temperature. The influence parameter of the gradient theory is estimated as 0.785ab2/3 in terms of the attractive and repulsive van der Waals parameters using the Lennard-Jones potential. The predictions made with the Mohanty-Davis equation of state agree better with experimental data than those made with Peng-Robinson, even for nonpolar fluids.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380512
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  • 9
    Electronic Resource
    Electronic Resource
    Removal of VOCs from groundwater using membrane-assisted solvent extraction (1994)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 40 (1994), S. 166-177 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A membrane-assisted solvent extraction (MASX) system coupled to a membrane-assisted distillation stripping (MADS) system for use in decontaminating ground-water is evaluated. Volatile organic compounds (VOCs) in the groundwater are extracted in the MASX unit using a sunflower oil solvent. In the MADS unit, VOCs are stripped from the sunflower oil, which is recycled to the MASX unit. Thermodynamic data for the sunflower oil-water-VOCs system were measured. The results were used along with published membrane mass-transfer data to design MASX and MADS modules.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690400119
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  • 10
    Electronic Resource
    Electronic Resource
    Lone-pair charges and structural effects (1990)
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 3 (1990), S. 255-259 
    Details
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The lone-pair charge, Qlpf, of a base B is a (theoretically calculated) measure of the amount of charge on the lone pair of B that binds to an acid Av (v = 0, 1) in an acid-base reaction. It is shown how they can be used for the quantitative study of structural effects on gas-phase proton affinities, vertical ionization potentials and hydrogen-bonding basicities.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/poc.610030408
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