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Digitale Medien

Electronic structure and polarizabilities of some heterocycles: I. Hydroxypyrazoles and related systems (1995)

Neykov, Georgi D. ; Enchev, Venelin ; Monev, Valentin ; [weitere]

Springer

Molecular engineering 5 (1995), S. 347-361

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ISSN: 1572-8951

Schlagwort(e): Polarizabilities ; pyrazolones ; hydroxypyrazoles ; tautomerism ; electronic structure ; excited states ; nonlinear optics

Quelle: Springer Online Journal Archives 1860-2000

Thema: Chemie und Pharmazie

Notizen: Abstract The (hyper)polarizabilities of different tautomer forms of hydroxypyrazoles and pyrazolones have been calculated by the finite-field procedure in the MNDO approximation and the sum of states formalism in the PPP approximation, with all singly- and doubly-excited electronic configurations in the CI method. It was shown that while in the ground electronic state the values of the (hyper) polarizabilities are not essentially different, in the first excited singlet Franck-Condon state an increase of the molecular polarizabilities of some tautomers is observed. This increase is attributed to a specific change in the electronic structure of the excited state, demonstrated by the localization of the electronic transition in the different pyrazolone tautomers. The electron-donor capabilities of phenyl-substituted hydroxypyrazoles and pyrazolones are discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF01004016

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Digitale Medien

Syntheses and Structures of 2-(O-Acylhydroxyimino)-1,3-indandiones (1987)

Minchev, Stoyan ; Nedev, Hinyu ; Enchev, Venelin

Weinheim : Wiley-Blackwell

Liebigs Annalen 1987 (1987), S. 375-376

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ISSN: 0170-2041

Schlagwort(e): Chemistry ; Organic Chemistry

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Chemie und Pharmazie

Notizen: 2-(O-Acetylhydroxyimino)-1,3-indandione (1) and 2-[O-(N-tert-Butyloxycarbonylglycyl)hydroxyimino]-1,3-indandione (2) have been synthesized by the mixed anhydrides method. The infrared and the 13C-NMR spectra, as well as the quantum chemical calculations show that this kind of active esters has the structure I.

Zusätzliches Material: 1 Ill.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1002/jlac.198719870337

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Digitale Medien

Tautomerism in 2,2′-bipyridyl-3,3′-diol (1996)

Enchev, Venelin

New York, NY : Wiley-Blackwell

International Journal of Quantum Chemistry 57 (1996), S. 721-728

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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: Three stable tautomeric forms, dienol (DE), ketoenol (KE), and diketo (DK), of 2,2′-bipyridyl-3,3′-diol BP(OH)2 were found in this study, using the semiempirical AM1 and MNDO-PM3 and ab initio (4-31G basis set) methods. All calculations were carried out without any symmetry restrictions. There is a good agreement between the ab initio calculated and experimentally obtained structural parameters for the DE tautomer. Transition structures, corresponding to the DK → KE and KE → DE processes have also been found. On the basis of the results from the present work, an asynchronous (two-step) DK → KE → DE mechanism of the IPT reaction in BP(OH)2 is proposed. © 1996 John Wiley & Sons, Inc.

Zusätzliches Material: 2 Ill.

Materialart: Digitale Medien

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