Unimolecular processes in vibrationally highly excited cycloheptatrienes. II. Steady-state photoisomerization

Abstract

The steady‐state unimolecular photoisomerizations of cycloheptatriene, 7‐methyl‐cycloheptatriene, and 7‐ethyl‐cycloheptatriene have been studied at wavelengths between 238 and 289 nm. The reactions proceed via vibrationally highly excited electronic ground state molecules. The specific rate constants k (E) for the unimolecular aromatizations and H‐atom shifts are derived and compared with statistical calculations. Absolute values of the average step sizes <ΔE≳ for energy transfer of highly excited molecules are obtained via calibration of Stern–Volmer curves against specific rate constants from thermal isomerization experiments.