Effect of aromatic donor upon sensitized cis–trans isomerization of but-2-ene

Abstract

Benzene molecules with fluoro- and trifluoromethyl-substituents have been used to sensitize the cis–trans isomerization of but-2-ene in the gas phase at 25 °C and various exciting wavelengths. For most compounds studied, the decay ratio of the olefin triplet to cis- and trans-ground-states was found to be unity, in agreement with published reports, but for two disubstituted benzenes, the cis–trans isomerization was shown to predominate over the trans–cis. The results are discussed in relation to the triplet energy levels of the aromatic molecules and mechanisms of sensitized isomerzation proposed previously.