Dissociation dynamics of phenetole cations by photoelectron photoion coincidence.

The dissociation rates of phenetole ions have been measured as a function of the ion internal energy by the method of photoelectron photoion coincidence spectrometry. The loss of ethylene to produce the phenol ion is the only dissociation pathway from its onset at 9.17 eV up to at least 12 eV. An activation energy of 1.64 ± 0.06 eV with an assumed activation entropy of + 18 ± 4 cal/mol-K is derived from fitting the statistical theory decay rates to the measured rates. The transition state energy lies ∼ 1 eV below the thermochemical dissociation limit to the C2H 5 (+) + C6H5O · products. It is thus unlikely that an ion-radical complex is involved in the production of the phenol ion.