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Digitale Medien

L'utilisation d'orbitales localisées dans l'étude théorique des molécules (1974)

Leroy, Georges ; Peeters, Daniel

Springer

Theoretical chemistry accounts 36 (1974), S. 11-24

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ISSN: 1432-2234

Schlagwort(e): Localized orbitals ; Unsaturated hydrocarbons ; Transferability of localized orbitals

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract The systematical study of the localized orbitals and their properties has been extended to the unsaturated hydrocarbons. The six simplest alkenes have been studied and fairly good transferability of the bond orbitals and their associated matrix elements may be pointed out. The influence of the neighbourhoods as well as the relative orientation of the bonds is discussed. These results lead to the use of a simple parametric procedure expressing the molecular orbitals as a combination of bond orbitals (LCLO-SCF-MO). This procedure is applied to saturated and unsaturated hydrocarbons, even conjugated hydrocarbons may be treated. Some original applications show that the results obtained by our procedure are comparable with the full ab initio calculations.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00549146

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2

Digitale Medien

Etude théorique de la molécule de diazométhane (1974)

Leroy, Georges ; Sana, Michel

Springer

Theoretical chemistry accounts 33 (1974), S. 329-338

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ISSN: 1432-2234

Schlagwort(e): Diazomethane

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract In this work we have calculated the electronic structure of diazomethane using Hehre's Gaussian-70 program with STO-3G and 7s 3p atomic basis sets. We have also estimated some thermodynamic properties of this compound. The theoretical results allow us to propose a description of the chemical bonds in CH2N2.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00551160

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3

Digitale Medien

Calculations on the Polymerization Process of Some 1,1-Disubstituted Cyclopropanes: I. The Initiation Step (1998)

Peeters, Daniel ; Leroy, Georges

Weinheim : Wiley-Blackwell

Liebigs Annalen 1998 (1998), S. 1397-1402

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ISSN: 1434-193X

Schlagwort(e): Polymerization process ; Ab initio calculations ; 1,1-Disubstituted cyclopropanes ; Polymerization enthalpies ; Transition state ; Energy barriers ; Chemistry ; General Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: Ab initio calculations on the initial steps of the polymerization process of 1,1-dicyano-, -difluoro- and -di-methyl-substituted cyclopropanes are presented. Polyme-rization enthalpies determined by model calculations show the thermodynamic feasibility of the process. The reaction mechanism of the first step is further discussed by considering initiation by various species such as Hq, OHq, and CH3q (q = +, 0, -). Transition structures and energy barriers are obtained for all species, allowing discussion of the reaction mechanism and an estimation of the kinetic feasibility. The Hartree-Fock structures at the 6-31+G(d, p) level have been fully optimized and electron correlation has been introduced at the MP2 level for some selected reaction mechanisms.

Materialart: Digitale Medien

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4

Digitale Medien

A theoretical approach to the thermochemistry of the polymerization of some derivatives of the monomers CH2=X (X = CH2, NH, O) (1997)

Leroy, Georges ; Dewispelaere, Jean-Pierre ; Wilante, Claude ; [weitere]

Weinheim : Wiley-Blackwell

Macromolecular Theory and Simulations 6 (1997), S. 729-739

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ISSN: 1022-1344

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: In this work, we have calculated the thermodynamic parameters of the polymerization of some derivatives of the species CH2=X (X = CH2, NH, O), using ab initio methods of quantum chemistry and the usual formalism of statistical thermodynamics. It is shown that the Gibbs functions ΔGp°(l, c) corresponding to CH2=NOCH3, CNCH=NCN, CF2=O and all the percyano derivatives are largely positive which indicates that the spontaneous (radical or ionic) chain polymerization of these monomers is thermodynamically prohibited.

Zusätzliches Material: 8 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mats.1997.040060404

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5

Digitale Medien

A theoretical approach to the thermochemistry of radical and anionic polymerizations of various unsaturated monomers (1996)

Leroy, Georges ; Dewispelaere, Jean-Pierre ; Benkadour, Hanan ; [weitere]

Weinheim : Wiley-Blackwell

Macromolecular Theory and Simulations 5 (1996), S. 269-289

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ISSN: 1022-1344

Schlagwort(e): Chemistry ; Polymer and Materials Science

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie , Physik

Notizen: In this work, we have calculated the thermodynamic parameters of the first steps of the free radical and anionic polymerizations of various unsaturated monomers, using ab initio methods of quantum chemistry. The enthalpies and entropies of polymerization were estimated assuming that they correspond to those of the model reaction A = B(p) + HABAH(p′) → HABABAH(p′) where p and p′ stand for the physical state of the considered species. The enthalpies of polymerization were rationalized using the equation ΔH0p = -ΔΣ NABEAB + SE(A = B) + SE(HABAH) - SE(HABABAH) where NAB is the number of A — B bonds, EAB the corresponding bond energy, - ΔΣ NABEAB the variation of the sum of the bond energy terms, and SE(X) the thermodynamic stabilization energy of compound X. The preferential mode of polymerization of each monomer was derived from the enthalpies of the initiation and initial propagation steps of the two types of polymerization. Thus, we were able to make some comments concerning the feasibility of the polymerization of the monomers under consideration.

Zusätzliches Material: 12 Tab.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/mats.1996.040050208

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6

Digitale Medien

All-electrons band structure of Polyene (1971)

André, Jean-Marie ; Leroy, Georges

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 5 (1971), S. 557-563

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ISSN: 0020-7608

Schlagwort(e): Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: In this work, we report an all-electron SCF-LCGO-CO computation for the ground state wave-function of an infinite polyenic chain. This work demonstrates that ab initio calculations on the electronic structure of polymers become actually feasible. Our results are compared with previously obtained semi-empirical ones.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/qua.560050509

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