On the loss of ethylene from [C3H7O]+ ions of structure documentclass{article}pagestyle{empty}begin{document}$ {rm CH}_{rm 3} {rm CH}_{rm 2} mathop {{rm CHOH}}limits^{rm + } $end{document}

The results of some ³C and ²H labelling experiments plus some measurements of reaction thermochemistry and translational energy releases, permit a significant simplification of the mechanistic pathways by which [C₃H₇O]⁺ ions of structure fragment by loss of C₂H₄. The relationships between these ions and some of their isomeric forms are explored and clarified.