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

E.s.r. spectra have been recorded for CH₂CHĊHSBu ^t and HC≡CĊHSBu^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^tSĊHCH ₂Ph and CH₃OĊHCH₂Ph prefer staggered conformations.