MRCISD studies of the dissociation of vinylhydroperoxide, CH2CHOOH: there is a saddle point.

Multireference ab initio methods are used to investigate the dissociation of vinylhydroperoxide CH(2)CHOOH into vinyl oxide and hydroxide radicals. In contrast to some previous studies, which claim the reaction has no saddle point, our calculations confirm that the dissociation is associated with a kinetic barrier (transition state). We further propose the existence of a hitherto undiscovered radical-radical complex on the reaction path. The computed reaction energetics are used to estimate VHP dissociation rates, and the results are discussed in the context of atmospheric ozonolysis pathways. Qualitative aspects of the dissociation of larger, substituted vinylhydroperoxides are also discussed.