Irkutsk State University

Using dipole moments as an example, we study the possibilities of calculating the properties of open-shell systems (radicals) using methods based on the third-order algebraic-diagrammatic construction approximation for the electron propagator and the second-order intermediate state representation formalism (ADC(3)/ISR(2)), designed to treat processes associated with electron detachment and attachment. For the purpose of calculating neutral radicals with an unpaired electron ( S = 1/2 ), the IP and EA variants of the method are applied to the corresponding anion and cation with closed electron shells. This allows calculations to be performed based on the restricted Hartree–Fock method and eliminates problems associated with the use of the unrestricted Hartree–Fock method for open shells in the direct consideration of radicals, such as poor convergence of the iterative process, spin contamination of the wave function, and doubling of the number of molecular orbitals. The dipole moments of the radicals NH _2^∙ , CN ^∙ , NO _2^∙ , OH ^∙ , HO _2^∙ , FO ^∙ , SF ^∙ , ClO ^∙ , CH ^∙ , NO ^∙ , and PO ^∙ in their ground states are calculated. The results obtained are in good agreement with the available experimental data.

The article presents a quantum-chemical analysis of the mechanism of formation of dispiroketals from 2-methylcyclohexanone and phenylacetylene in a superbasic KOH/DMSO medium. The conformations of the starting ketone, the formation pathways of intermediate products and isomers, and the energy barriers of the key stages were studied by the B2PLYP-D2/6-311+G**//B3LYP/6-31+G* methods. It was established that the reaction occurs in three stages: nucleophilic ethynylation of ketone, formation of semiketal, and intramolecular O-vinylation. The rate-determining process is the two-stage process of addition of the second ketone molecule and subsequent O-vinylation. Of the eight possible diastereomers, only three are localized (SSSS, RSSR, SSSR), the final ratio of which is 7 : 2 : 1. The predominance of the SSSS isomer is associated with the thermodynamic stability and kinetically advantageous formation of the preceding alkoxide ion.

The kinetic and thermodynamic characteristics of the formation of dicyclohexyl disulfide from chlorocyclohexane and sodium disulfide both in the presence and absence of iodide ions were calculated by quantum-chemical methods. When estimating the free energy of dissociation of sodium sulfide for mechanism calculations, a combined approach B2PLYP-D3/6-311+G(2df,2p)//B3LYP/6-31+G(d) with geometry optimization within the IEFPCM continuum model was chosen. It is shown that the reaction does not proceed via the SN1 mechanism because of the greatly increased free energy during the formation of the cyclohexyl cation from both chloro- and iodocyclohexane. It is demonstrated that the rate-limiting step of the reaction is the SN2 substitution of the chloride ion in chlorocyclohexane. The free activation energy of substitution of chlorine by the iodide ion is 1.0 kcal/mol lower than that by the sodium disulfide anion. The interaction of the sodium disulfide anion with iodocyclohexane, in turn, occurs with a barrier 1.9 kcal/mol lower than with chlorocyclohexane. The lower activation barriers involving iodine explain the increase in the reaction rate of dicyclohexyl disulfide formation from chlorocyclohexane and sodium disulfide after the addition of potassium iodide to the reaction mixture.

The features of coastal full upwelling in August–September 2004 have been revealed based on the results of processing and joint analysis of high-frequency water temperature measurements at two moorings located in the southwestern part of Lake Baikal and reanalysis of the wind situation and surface currents using successive IR satellite surveys by the maximum cross-correlation method. Quantitative estimates of changes in the thermal structure at coastal and deep stations, the rate of rise and fall of water, and spatial and temporal variability of heat content have been obtained. The duration of minimum temperatures at the underlying horizons of the active layer during the upwelling period is 11–15 days, with a longer and more intense effect being manifested in the coastal zone.

This analysis of the general processes in the localized migration of lithium from the mantle according to the Romanyuk–Tkachev model as the ultimate mutual interaction between mantle plumes in Northeast Asia and in the Mongolia–Okhotsk slab through intermediate upper crustal magma chambers rests on the examination of mutual locations of intrusive bodies in the basement and in the sedimentary cover of the Siberian craton and of localization regions (as proved by drilling) containing commercial rare-metal brines with anomalously high concentrations of lithium in the natural reservoirs of the zone of retarded water exchange in the sedimentary cover of the major Angara–Lena artesian basin. It is shown how the region of brine occurrence that has anomalous lithium concentrations overlies in space the ring anomaly formed by the emplacement of a large pluton of the (hypothetical) Paleoproterozoic Baikal–Taimyr orogenic belt in the Early Proterozoic basement. On the other hand, a group of large deposits of lithium-bearing brines in the sedimentary cover (an analogue of an “ore field”) localizes in the band between the apical part of the giant Usolsky Sill to the west and the Baikal-Patomsky Folded Region (BPFR) foreland to the east. We are discussing the likely role played by large paleohydrothermal systems of magma bodies in the formation of lithium haloes, in the process of its subsequent transfer of hydrothermal fluids, and concentration in naturally occurring brines beneath thick deposits of Cambrian salts.