Novel eliminations of neutral fragments from ions during mass spectrometry. Part V. Evidence for cyclisation processes in the elimination of methyl from stilbene analogues

Abstract

The elimination of a methyl group from diarylethylenes (I) and 1,4-diphenylbutadiene has been investigated by ¹³C-labelling. The results show that cyclisation of the molecular ion must occur and comparisons with photochemical reactions are examined. The cyclisation of the molecular ion of 1,4-diphenylbutadiene appears to follow Woodward-Hoffmann Rules for an excited state process; the formation of tropylium from this ion is discussed.