Unimolecular photochemistry of alkanethiols studied by photodissociation-photoionization mass spectrometry

Abstract

Unimolecular photodissociation of isomeric alkanethiols in the C 3 to C 8 size range was studied by using photodissociation-photoionization mass spectrometry. Photodissociation was performed with 193- and 248-nm radiation. The primary products were photoionized with coherent vacuum ultraviolet radiation and detected in a time-of-flight mass spectrometer. Three basic reaction channels were observed: C-S, C-C, and S-H bond dissociation. The branching ratios for fragmentation through these channels were found to be strongly dependent upon molecular structure and photodissociation wavelength. All compounds gave intense products of C-S bond dissociation. Photoionization and secondary fragmentation characteristics of the primary products suggested that complete statistical partitioning of the excess internal energy did not occur