By means of the electron-topologic approach, combining the methods of the pattern recognition theory and the electron and geometric description of the molecular systems under consideration, the totality of 52 sulphur-containing organic compounds is investigated. The electron-topologic activity fragment found allows to characterize correctly all the compounds of the totality and to describe successfully the influence of the structural changes in the molecular systems investigated on the garlic odor appearance.An important class of chemical compounds applied as additives for producing food flavourings is the series of sulphur-containing organic compounds possessing garlic aroma. Application of these compounds in food industry allows a considerable reduction of the valuable plant raw material. In this connection the synthesis of such compounds -flavourings with garlic aroma -is rather an actual task. At the first stage of its solution it is necessary to study the dependence of the exhibited odorant characteristics of the chemical structure.With the determination of the structure-activity relationship one may start the design of the novel compounds characterized by the found structural signs of the activity. At the final stage the directed synthesis is performed and a novel compound is investigated.In the present paper the results are given of the study of structure-odorant activity relationship for the initial sample of 52 sulphur-containing chemical com ounds. The studied series of the chemical compounds was divided into two classes, one of them (the active class g -26 molecules) including the compounds with the characteristic garlic nuance of the aroma, while the other one (non-active class -26 molecules) includes the compounds not possessing the garlic aroma.As it can be seen from Table 1 the samples of chemical compounds in both the classes are characterized by different types of molecular structures. Thus, for example, there are representatives of the acyclic, cyclic, aromatic sulphur-containing compounds, as well as the derivatives of the organic mono-, di-and trisulphides. The given consideration complicates the problem of the search of the structure-activity relationship and does not give the possibility to apply the general methods of the logico-structural analysis [I], oriented at the study of the same type of the compounds of the related structure. In this connection we have tried to use the electron-topologic method worked up earlier which proved useful at the study of the electronic and structural peculiarities of the organic compounds forming their ambergris aroma [2]. This is first of all connected with the fact that at such an approach using Y

Manifestation of the dynamic solvent effect (DSE) on the charge recombination (CR) kinetics of photoexcited donor-acceptor complexes in polar solvents has been investigated within the framework of the multichannel stochastic model. The model takes into account the reorganization of both the solvent and a number of intramolecular high-frequency vibration modes as well as their relaxation. The non-Markovian solvent dynamics is described in terms of two relaxation modes. The similarities and differences inherent to ultrafast charge transfer reactions occurring in the nonequilibrium and thermal regimes have been identified. The most important differences are as follows: (1) the DSE is strong in the area of weak exergonicity and is weak in the area of strong exergonicity for thermal reactions, whereas for the nonequilibrium reactions, the regions of strong and weak DSEs are reversed; (2) an increase in the electronic coupling value results in a decrease in the magnitude of DSE for nonequilibrium electron transfer and in its increase for the thermal reactions; and (3) the two-staged regime most clearly manifests if the reorganization energy of the relaxation modes noticeably exceeds the CR free-energy gap. With an increase in electronic coupling, the kinetics approaches the exponential regime because in the limit of strong electronic coupling, the reaction includes only single, nonequilibrium, stage.

acridine-1.9(2H,5H)dion) with quadrupolar motif has been synthesized and its stationary and transient spectra have been measured. Stationary absorption and fluorescence spectra as well as nonstationary spectra show no signs of symmetry breaking (SB) in aprotic solvents, even of high polarity. The specific features of SB are revealed in alcohol solvents through a considerable red shift of stationary fluorescence spectra and the appearance of a new excited state absorption band in transient absorption spectra. SB is due to the formation of asymmetric strong hydrogen bonds, mainly on one side of the molecule. An unexpected regularity of symmetry breaking is found in mixtures of aprotic dimethylformamide and protic methanol, where methanol acts as a fluorescence quencher. It is revealed that there is no quenching as long as the methanol concentration is less than the critical value of 9 M. This leads to the conclusion that SB in such mixtures is possible only if the concentration of the protic solvent exceeds a certain threshold value.

Control of charge transfer requires knowledge of its detailed mechanism. Due to the large number of known mechanisms, the identification of the mechanism in specific systems is a challenge so far. In this article we propose the idea of how to distinguish between thermal and nonequilibrium modes of charge recombination in excited donor-acceptor complexes. Simulations of the effect of solvent relaxation time scale on ultrafast charge recombination kinetics in photoexcited donor-acceptor complexes within the framework of the multichannel stochastic model have shown that a series of regularities inherent to the thermal and nonequilibrium charge transfer can strongly differ. Among them there are opposite regularities, for example, the dependence of the dynamic solvent effect on the free energy gap. In particular, theory predicts that in ultrafast charge recombination of excited donor-acceptor complexes the dynamic solvent effect is weak in the area of weak exergonicity and becomes stronger in the area of stronger exergonicity whereas for the thermal reactions an opposite trend is expected. Comparison of such trends with experimental data implemented in this article allowed establishing the regime in which the reaction proceeds. It is shown that observation of dynamic solvent effect in the region of strong exergonicity for ultrafast charge recombination is decisive evidence in favor of nonequilibrium mechanism.

By means of GLC-analysis on columns with different polarity phases the composition of the sulphur-containing volatiles obtained by the thermal treatment of the industrial broths and alkyl-mercaptopropanol was studied using flame-photometric detector specific for sulphur. The identification of the sulphur-containing compounds was realized using both retention indices and GLC-MS. The comparison of the composition of sulphur-containing flavour components of the industrial broth with that of its product with alkyl-mercaptopropanol was carried out.