An electron spin resonance study of 1-alkylthioallyl, 3-alkylthiopropynyl, and alkylthioalkyl radicals: an examination of spin delocalization by alkylthio groups

Abstract

E.s.r. spectra have been recorded for CH_–2CHĊHSBu^t and HCCĊHSBu^t. The hyperfine splitting constants indicate that considerable spin density is delocalized onto the SBu^t group. This group is a more effective acceptor of spin than alkyl, hydroxy, or alkoxy substituents, and comparable with that of an ethynyl substituent. The barrier to rotation about the C_α–S bond in AdSĊH₂ is greater than that about the C_α–O bond in AdOĊH₂ as a consequence of greater spin delocalization onto sulphur than onto oxygen. The mechanism of reaction of t-butoxyl radicals with sulphides is discussed. The Bu^tSĊHCH₂OCH₃ radical exists in an eclipsed conformation whereas Bu^tSĊHCH₂Ph and CH₃OĊHCH₂Ph prefer staggered conformations.