Solvatochromism of Heteroaromatic Compounds: VI. Comparison of the Empirical and Theoretical Approaches to Description of Solvatochromism in Nonspecific Solvation of Nitropyrazoles

The effect of nonspecific solvation on the long-wave absorption band in the UV spectra of isomeric nitropyrazoles was studied. The aprotic inert and aprotic protophilic solvents exert different spectroscopic effects. In the former solvents, the solvatochromism is mainly governed by orientation interactions, and in the latter solvents, along with the orientation interactions, the UV spectrum is appreciably influenced by the induction, polarization, and dispersion interactions, which is due to the presence of readily polarizable nonbonding electron pairs and/or a pi-electron system in molecules of such solvents.     

Trimethylsilylazoles Chemistry

In the review are summarized and analyzed the data on synthesis, chemical and physico-chemical characteristics of C- and N-trimethylsilylazoles. A special attention is paid to Dondoni reagent (2-trimethyl- silylthiazole) extensively used in the asymmetric synthesis.     

Reactions of terminal acylacetylenes with thiocarbohydrazones

The reactions of terminal acylacetylenes with thiocarbohydrazones give 2-(2-acyl-vinyl)thiocarbohydrazones or 2,2-bis(2-acylvinyl)thiocarbohydrazones depending on the reagent ratio. Benzoylacetylene reacts with thiocarbohydrazone ofp-dimethylaminobenzaldehyde to formS-[2-(p-dimethylaminobenzoyl)vinyl]isothiocarbodihydrazone. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2083–2085, October, 1998.     

Determination of electron affinity of carbonyl radicals by means of negative ion mass spectrometry

Appearance energies of [M-H](-) ions from carbonyl compounds R-CO-R' (R,R' = H, CH(3), NH(2), OH) have been measured by means of negative ion mass spectrometry in resonant electron capture mode. Values of electron affinity of the corresponding radicals, CH(2)&dbond;C(X)O, NH&dbond;C(X)O and O&dbond;C(X)O, have been determined. Copyright 1999 John Wiley & Sons, Ltd.     

Vicarious Nucleophilic Substitution of Hydrogen in Nitro-substituted Pyrroles, Azoles, and Benzannelated Systems Based on Them. (Review)

Published data on the participation of nitro-substituted pyrroles, azoles, and their benzannelated derivatives in vicarious nucleophilic substitution are reviewed.     

Investigation of benzimidazoles. III—transmission of the substituent effects in 2-substituted 1-methylbenzimidazoles studied by 13C nuclear magnetic resonance

The influence of substituents on the ¹³C NMR chemical shifts of 2-substituted 1-methylbenzimidazoles has been investigated. The electronic effects of the substituents are transmitted to C-4 and C-7 mainly by the resonance mechanism, and to C-5, C-6 and N-CH₃, by approximately equal contributions of the resonance and inductive components. A critical analysis of the share in the transmission of substituent effects through the ‘pyridine-type’ and ‘pyrrole-type’ nitrogen atoms is given.     

Calculation of the electron structures and electronic spectra of 3-chloro- and 3-amino-1,2,4-triazole derivatives

3-Chloro- and 3-amino-1,2,4-triazole derivatives were subjected to a theoretical study by means of quantum-chemical calculation by the Pariser-Parr-Pople method. The experimentally observed electron transitions were assigned. The Cl atom and the NH₂ group in the 3 position of 1,2,4-triazole subject the electron system of the heteroring to substantial perturbation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 698–700, May, 1977.