ELECTRON AND PROTON-TRANSFER REACTIONS OF SIMPLE ALDEHYDE AND KETONE RADICAL CATIONS AND THEIR ENOL AND DISTONIC ISOMERS

The reactivity of the keto and enol isomers of the acetaldehyde and ac etone radical cations and the keto, enol and distonic isomers of the p ropanal radical cation was examined in the gas phase by using Fourier- transform ion cyclotron resonance mass spectrometry. The results obtai ned show that these radical cations do not readily undergo isomerizati on within a gas-phase collision complex. Further, the ions favor elect ron transfer to proton transfer whenever the former reaction is thermo dynamically accessible. This reaction can occur either directly by abs traction of an electron by the radical cation or indirectly by a more complex mechanism that is likely to involve energetically favorable pr oton and hydrogen atom transfers within the ion-molecule complex (a H/H-. shuttle). The above knowledge can be utilized in the differentiat ion of the keto, enol, and distonic isomers of simple carbonyl-contain ing radical cations. (C) 1997 Elsevier Science B.V.