Nanosecond laser flash photolysis of 1-anisyl-2,2-diphenylvinyl bromide in acetonitrile and acetic acid

Abstract

Nanosecond time-resolved spectroscopy shows that intermediates are produced upon laser flash excitation of 1-anisyl-2,2-diphenylvinyl bromide in acetonitrile and in acetic acid media. In acetonitrile optical absorption and electrical conductivity studies show the intermediacy of vinyl cations. In pure acetic acid no free ions are formed on laser flash excitation. The presence of polar additives in acetic acid is necessary for transient vinyl cations to appear. The cation is formed in parallel with a short-lived species, which is tentatively assigned as a radical pair or a tight ion pair. The least amount of additive necessary to produce a detectable quantity of vinyl cations depends on the nature of the additive. The quenching of the intermediate cations in acetonitrile and acetic acid media with bromide and acetate ions displays selectivity in agreement with the selectivity observed in steady-state irradiations.