ELECTRON STRUCTURE OF RADICALS OF SULFOXYLIC ACID ESTERS

Abstract

The density functional theory B3LYP/6-311++G(3df,3pd) has been used to optimize the geometry of homologues of a series of sulfoxylic acid ester radicals and to obtain the electron density distributions of the first nine compounds. The hydrogen bond presented in the initial molecules of the unbranched esters of sulfoxylic acid between the hydrogen of the second carbon atom of the alkyl chain (from the ester bond) and the oxygen of the hydroxyl group of the sulfur-containing fragment (-C(Н)H-CH2-O-S-ОН) and the corresponding cycle are not observed in the radicals. The fragmentation of the structures into topological groups of CH3, CH2, and (-O-S-O)● has been proposed and their electron integral characteristics are presented including charges, unpaired electron density, energy, and volume. The steric effect of the fragment (-O-S-O)● has been established and its inductive effect has been considered based on the groups charge parameters changes triggered by an increase in the hydrocarbon chain. The scale of group electronegativities of the studied homologues has been constructed by comparing the charges of topological groups. The fact that the radical center corresponds to the fragment (-O-S-O)● has been demonstrated by the spin density delocalization results (having the largest fraction on the sulfur atom (0.57), slightly less fraction on the oxygen atom with a free valence (0.32) and an insignificant fraction on oxygen atom using the ether bond (0.10)). The increment value of the total energy contributed by the CH2 group of each subsequent homologue of the series under the study has been estimated. It is 103260 kJ/mol. The evaluation of the “standard” value of the groups’ total electron energy and the use of their relative energy (ΔE(R)) for comparing with ΔE(R) of molecules and radicals of other homologous series have been described. A decrease in the volumes of the two closest to the sulfur-containing fragment CH2 groups caused by an outflow of electron density from them toward the fragment (-O-S-O)● has been noted.