Gas‐phase ion–molecule reactions of thioic and dithioic acid derivatives. Condensation reactions with alkenes and alkynes

A Fourier transform–ion cyclotron resonance study of thioacyl compounds as binary mixtures with unsaturated hydrocarbons has revealed that thioacetylium ions CH 3 CS + generated by electron fragmentation fail to thioacyl‐ate even the most reactive aromatic hydrocarbons. Among the hydrocarbons studied, only 3‐hexyne and 2,4‐dimethyl‐2,5‐hexadiene were observed to react with CH 3 CS + . Apart from proton‐transfer reactions, the major ionic reaction of thioesters with arenes, alkynes and alkenes is condensation of the molecular ion of one component, usually the ester, with a neutral molecule of the other, resulting in the cleavage of the SC alkyl bond of the thioester. The nature of this reaction is discussed and a possible mechanism is suggested.