Unusual lability of intramolecular coordination bond O→Si <Emphasis Type="Italic">N</Emphasis>-(trifluorosilylmethyl)succinimide

According to IR spectroscopy data and ab initio quantum chemical computations, a novel representative of intracomplex organosilicon compounds — N-(trifluorosilylmethyl)succinimide (I) possesses an anomalously high sensitivity to medium effects. Coordination bond O→Si of the compound I is strong in the solid phase and polar medium, and weak in its isolated molecules. Geometric parameters calculated for the molecule I in polar medium correspond to X-ray diffraction data.     

Biotransformation of Aspen Lignin by the Fungus Trametes villosus

Quantitative ¹ H and ¹³ C NMR spectroscopies demonstrate that biotransformation of aspen wood by the fungusTrametes villosusresults in oxidation and destruction of lignin with cleavage of C-C alkyl-alkyl bonds in side chains and partial demethoxylation in addition to cleavage of lignocarbohydrate bonds. New C _ar -O-C bonds form while lignin is being destroyed at alkyl-alkyl bonds. Cleavage of rings and destruction of C _ar -C bonds was not observed.     

Molecular Structure of Complexes with Bifurcated Hydrogen Bond: III. Solvate H-Complexes Formed by Trifluoromethanesulfonamide and Its Cyclic Dimer

According to the data of IR spectroscopy, dielcometry, and B3LYP/6-31G* quantum-chemical calculations, trifluoromethanesulfonamide homoassociates in weakly basic protophilic media are converted into 2 : 1 solvate H-complexes. Cyclic trifluoromethanesulfonamide dimer decomposes in heteroassociate with dioxane with a composition of 1 : 3. Cyclic trifluoromethanesulfonamide dimer with dioxane forms a 1 : 4 H-complex with bifurcated (three-center) hydrogen bond involving the bridging hydrogen atom of the NH group (NH?O).     

Formation and conversions of terplexes in quenching of triplet state of p-chloranil by durene

Interaction of the triplet state of chloranil with durene in dioxane leads to the formation of short-lived polar complexes with a 11 composition (exciplex) and a 12 composition (terplex). One of the channels for destruction of the terplex is proton transfer between its counterions.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1295–1299, June, 1990.     

Solvatochromism of heteroaromatic compounds: XXIX. Configurational isomerism of H complexes of phenols with amides and esters

Phenol and amides and esters in carbon tetrachloride form an H complex with an OH n bond, whose configurational isomers differ from each other by the direction of the hydrogen bond and, as a result, by the value of the spectral shift. Structural details of such configurational isomers and solvatochromism of their IR absorption bands are discussed.     

Geometric factor in prototropic reactions of neutral and charged radicals

Conclusions The difference between the rate constants of thermodynamically favorable proton-transfer reactions between NH- and OH-containing radicals and heterocyclic bases and those diffusion-controlled reactions is due to the reactivity anisotropy of the reagents.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 31–34, January, 1989.     

Solvatochromism of Heteroaromatic Compounds: XIV. 5-Amino-1-methyl-4-nitropyrazole and Its Analogs

The solvatochromism of H complexes of 5-amino-1-methyl-4-nitropyrazole and 2-nitroaniline derivatives in aprotic protophilic media was described on a quantitative level with the aid of Kamlet-Taft empirical parameters. Specific solvation affects only one of the two long-wave bands, namely that corresponding to an electronic transition involving orbital electron density transfer from the H-bound nitrogen atom. When such transfer does not occur, which is typical of the second transition, specific solvatochromic effect is either weak or absent.