Gas-phase unimolecular reactivity of C3H7O+ cations: A combined mass spectrometric molecular orbital study

The unimolecular dissociations of the two isomeric ions [CH3CH2CHOH](+) (1) and [CH3CH2OCH2](+) (2) were re-examined. Molecular orbital calculations conducted at the MP2/6-31G*//HF/6-31G*+ZPE level were used to characterize the corresponding potential energy profile, The experimental data were completed by a Fourier transform ion cyclotron resonance spectrometric investigation on the system [CH2H](+)+C2H4 and by a study of various metastable [C3H7O](+) ions, The isomerization pathway of lowest energy connecting 1 and 2 involves two ion-neutral complexes between protonated formaldehyde and ethene. The isomerization 1 reversible arrow 2 is typically a complex mediated reaction since the key step consists simply of the reorientation of the two partners [CH2OH](+) and C2H4 inside the ion-neutral cage. The model is demonstrated to account for the H-D exchange observed during the dissociation of variously deuterated species. (C) 1997 by John Wiley & Sons, Ltd.