Mass spectrometric investigation of phenylthiovinyl chlorides

Three isomeric phenylthiovinyl chlorides (β-, E and Z, and α-) have been examined under EI and FI conditions with particular attention paid to the fragmentation leading to [C₈H₇S]⁺ ions via loss of Cl˙. Kinetic energy release data, MIKE and CAD MIKE spectra obtained with these precursors, as well as with model compounds, suggest the thioacylium ion PhCH₂CS⁺ as the predominant structure observed for the [C₈H₇S]⁺ species in all cases examined. A comparison is made with the solution behaviour of incipient β-thiovinyl carbenium ions, which are known to rearrange to the S-bridged thiirenium structure.