The isomerization of 1-methylcyclopropene: A multichannel unimolecular reaction induced by overtone excitation

Abstract

The distribution of products resulting from the isomerization of gas phase 1-methylcyclopropene (1) induced by C–H stretch overtone excitation has been studied in a search for mode specific effects. Quantum yields for the disappearance of 1 have been determined as a function of the total pressure of a mixture of 1 and methylenecyclopropane and of the added bath gases SF6 and Ar using a combination of intracavity dye laser photolysis and end product analysis by gas chromatography. These data, together with the ratios of the yields of the major isomerization products, are adequately reproduced by RRKM theory and a weak collisional energy transfer model: no evidence for mode specificity is obtained. The experimental data demonstrate the importance of inefficient collisional energy transfer but allow some conclusions to be drawn concerning the applicability of RRKM theory which are not strongly dependent upon the details of the energy transfer model.