Dissociation dynamics of halotoluene ions,production of tolyl,benzyl and tropylium ([C7H7]+)ions

The dissociation rates and energetics of the loss of halogen atoms from energy-selected halotoluene ions were investigated by photoelectron photoion coincidence (PEPICO) and collisional activation (CA) mass spectrometric experiments. Dissociation onsets, determined from the dissociation rates measured as a function of the internal energy of the parent ion, revealed the formation of three C₇H₇]⁺ isomers, which were identified, on the basis of the CA data, as the tolyl, benzyl and tropylium ions. All of the ions investigated produced a mixture of isomeric ions. Only iodotoluene ions produced any tolyl product ions by a direct bond cleavage. The bromo- and chlorotoiuene ions produced mixtures of benzyl and tropyl ions. The observed two-component decay rates of the iodotoluene ions revealed the participation of a lower energy C₇H₇I]^{+ ˙} isomer in the dissociation process. The identity of this isomer is not known but it probably does not have the cycloheptatriene ion structure because considerable kinetic energy was released in this dissociation.