Mass spectra of aromatic and acetylenic compounds. Part VI. The electron impact-induced rearrangements of substituted phenylacetylenes

The mass spectra of [²H₁]phenylacetylene shows 100% H/D randomisation in the molecular ion prior to expulsion of an acetylene fragment. In analogous benzene-substituted phenylacetylenes 70-100% H/D randomisation occurs in the molecular ion or some subsequent fragment. Symmetrical intermediates are proposed to account for the scrambling and it seems likely that carbon-carbon bond fission takes place prior to formation of these intermediates.