The problem of the azatropylium ion: Hydrogen elimination from the molecular ion of γ‐picoline

Comparison of the mass spectrum of γ‐picoline with that of analogues, specifically deuterated in the methyl group, the ring or both, has shown that the molecular ion loses the α,β and methyl hydrogen atoms (ω‐hydrogen') in the ratio 1.43: 1: 1. 13. The same trend is found for the elimination of HCN from the molecular ion. Moreover, a value of 1.52 is found for the isotope effect, expressing the favoured loss of H over D, irrespective of its position.