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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 16 (1995), S. 1067-1080 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Density functional calculations on several classes of organolithium compounds are described. The compounds studied include lithium bonds to carbon, oxygen, and nitrogen and are representative of most types of organolithium compounds that have appeared in the recent literature. The computational results are compared to those using MNDO, which has been shown to have some serious deficiencies in compounds involving carbon-lithium bonds, and to PM3 results, which offer some improvement over MNDO for many organolithium compounds. Most of the density functional calculations with a large basis set are in good agreement with available ab initio and experimental data. Calculated carbon-lithium bond lengths were slightly shorter than those calculated by other ab initio methods and were substantially longer than those calculated by MNDO, which is known to underestimate carbon-lithium bond lengths severely. Dimerization energies of methyllithium, calculated by DMol, were also in good agreement with those of other ab initio calculations. Lithium-nitrogen bonds in lithium amides were calculated to be slightly shorter by DMol than by MNDO, although the two methods were in qualitative agreement for this type of compound. © 1995 by John Wiley & Sons, Inc.
    Additional Material: 24 Tab.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 14 (1993), S. 809-817 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The two-step hydrolyses of substituted polyglycolic acids are modeled by the semiempirical MNDO Hamiltonian using small molecule analogs to determine the effect of the alkyl substituents on the reaction and activation enthalpies. Reaction enthalpies remain reasonably constant up to three carbons, before becoming less exothermic for large alkyl substituents. Activation enthalpies show patterns that can be explained by steric effects. © 1993 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 15 (1994), S. 241-248 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Hyaluronic acid and its derivatives are absorbable polysaccharides which are used extensively in cosmetics and as biomaterials. Two possible mechanisms of degradation, involving an oxocarbenium ion and the corresponding radical cation, are examined by modeling of the saccharide ring and the effects of various ring substituents on the two possible mechanisms. © 1994 by John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 949-960 
    ISSN: 0887-624X
    Keywords: dimethyltitanocene ; biodegradable polymers ; poly(glycolic acid) ; surface degradation ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The purpose of this research was to selectively alter the rate of surface degradation of linear aliphatic polyesters without adversely affecting their bulk properties by way of functional group transformation, where the surface ester linkages would be converted to vinyl ether functionalities with dimethyltitanocene. It has been observed that dimethyl titanocene causes surface degradation of poly (glycolic acid) without adversely affecting its bulk properties, such as Mv, bursting strength, and thermal properties The vinvl ether resulting from the conversion of the PGA ester groups was unstable under ambient conditions, and further reacted by polymer chain scissioning, as was observed from measurements of molecular weight. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1657-1663 
    ISSN: 0887-624X
    Keywords: solid electrolytes ; poly(ethylene oxide) ; poly(2vinylpyridine) ; conductive polymer blends ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(ethylene oxide) (MW 600,000)/poly(2vinylpyridine) (MW 200,000)/LiClO4 blends have been prepared by the solution blending process. The ionic conductivities of the blends containing lower weight fractions (15, 17.5, 20 and 22.5%) of poly (2vinylpyridine) initially increases as the salt content is increased, reaches a maximum at an ethylene oxide/Li+ mole ratio of 10 and decreases as the salt content is further increased. Blends, which have higher weight fractions of poly(2vinylpyridine) (25 and 35%) display different electric behavior, i.e., the ionic conductivity continously increased as the salt content is increased to an ethylene oxide/Li+ mole ratio of 2. Thermal, 7Li solidstate NMR and semiempirical MNDO molecular orbital studies indicate that this contrasting behavior may be explained by the structure and ratios of the solvates (mixed solvate or homosolvate) of LiClO4 present in the blends. © 1995 John Wiley & Sons, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Anionic polymerization of 2-vinylpyridine shows significant solvent effects on the polymer stereochemistry. Polymerization with butyllithium in tetrahydrofuran (THF) yields a largely isotactic polymer, while polymerization with butyllithium in tetramethyl-ethylenediamine (TMEDA) results in a material with nearly the same stereochemistry as radical polymerization. Semiempirical molecular orbital calculations were used to explain these solvent effects.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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