Electron spin resonance studies of γ-irradiated lithium alkyls. The methylene anion

Abstract

Exposure of methyl lithium to ⁶⁰Co γ-rays at 77 K gave a radical having a 1:2:1 triplet e.s.r. spectrum characteristic of ·CH^–₂ anions. The perdeuterated compound gave a singlet due to ·CD^–₂ anions. Similarly, ethyl lithium gave a quintet due to (CH₃ĊH)^– anions and isobutyl lithium gave a poorly resolved multiplet assigned to EtĊMe^– anions. No evidence for the tautomeric change (CH₃ĊH)^–→(CH₂[graphic omitted]CH₂)^– could be obtained. The fall in the β-proton hyperfine coupling on going from CH₃CH₂(26 G) to CH₃CH^–(21 G) is explained in terms of a decrease in hyperconjugation.