Investigations of structure and conformation. Part 11. Electron spin resonance spectra of sulphur- and oxygen-conjugated radicals derived from 1,3-dithiolan, 1,3-oxathiolan, and related compounds

Abstract

A variety of radicals with two α-heteroatom substituents (two sulphurs, a sulphur and an oxygen, and two oxygens), as well as in some cases an α-phenyl substituent, have been obtained by reaction of the parent compounds with Bu^t O· generated photochemically. E.s.r. spectra confirm that sulphur exerts a significant delocalizing effect (spin withdrawing parameter ca. 19%), and that when sulphur and oxygen α-substituents are both present the bending effect of the latter dominates. Two oxygen atoms at the radical centre induce significant bending except when a phenyl substituent is also conjugated with the unpaired electron; these effects are analysed on the basis of INDO and Hückel–McLachlan molecular orbital calculations.

Conformational effects in the sulphur-containing radicals are also reported.