Conformational analysis of imidoyl radicals by electron spin resonance spectroscopy

Abstract

A series of N-t-butylimidoyl radicals, RĊNBu^t, have been prepared by the reaction of t-butoxyl radicals with the parent imines, RCHNBu^t, and their e.s.r. spectra have been recorded. The n.m.r. coupling constants, ³J(CH–CHNBu^t), in the imines are related to the e.s.r. hyperfine coupling constants, a(H_β), in the imidoyl radicals by the expression a(H_β)/G = 3.53 ³J(CHCHNBu^t)/Hz – 8.48. A similar relationship has been identified previously between the aldehydes and the acyl radicals.

These results are rationalised on the assumption that the radicals have a σ-electronic configuration, and that similar intramolecular interactions in the imines and imidoyl radicals impose on them similar conformations.