PRODUCTION AND DECOMPOSITION OF LARGE ALKYL RADICALS

Large alkyl radicals and their unimolecular decomposition products are generated and detected by molecular beam photodissociation-photoioniz ation mass spectrometry. Alkyl radicals are prepared by photodissociat ion of the corresponding haloalkanes in the core of a free jet expansi on. Collisional cooling in the expansion stabilizes the primary produc ts and minimizes secondary reactions. The photolysis products are dete cted by photoionization with coherent vacuum ultraviolet radiation. Th is technique permits large (greater than or equal to C-6) n-alkyl radi cals and their subsequent low-energy decomposition reactions to be stu died. The n-heptyl and 5-methyl-1-hexyl radicals are found to decompos e by both C-C and C-H bond dissociation pathways. Direct beta(C-C) bon d dissociation is only a minor process, indicating that radical isomer ization precedes C-C and perhaps C-H bond dissociation.