Dissociation of fluorotoluene molecular ions: A theoretical study

Abstract

The potential energy surfaces (PESs) for the isomerizations and dissociations of the α-, o-, m-, and p-fluorotoluene molecular ions were determined using density functional theory molecular orbital calculations. Rice–Ramsperger–Kassel–Marcus model calculations were carried out to understand the kinetics of the isomerizations and dissociations based on the PESs obtained. Kinetic analysis showed that the interconversion among the four molecular ions was much faster than the dissociations at low energies. The main product was a mixture of the fluorotropylium and p-fluorobenzylium ions formed by the loss of H in the dissociation of all of the molecular ions investigated. At high energies, the α-fluorobenzylium ion was another important product in the dissociation of the α-fluorotoluene ion. A fluorine substitution effect on the C–H bond dissociation energy was observed, which was well explained by the valence bond theory.