Positive ion fragmentation mechanisms of some simple aldehydes and epoxides and trimethylene oxide

The metastable ion spectra of ethylene oxide, acetaldehyde, acetaldehyde-d4, propylene oxide, propionaldehyde and trimethylene oxide are presented. They reveal no reason to suppose that electron-impact-induced isomerisation of oxide to aldehyde structure occurs, although many spectral features are common to various members of this set. The spectra of phenylacetaldehyde and styrene oxide are compared, and the more plausible possibility of partial isomerisation in this case is discussed.