Hydrogen Migration and Vinylidene Pathway for Formation of Methane in the 193 nm Photodissociation of Propene: CH3CH=CH2 and CD3CD=CD2

Photodissociation channels and the final product yields from the 193 nm photolysis of propene-h 6 (CH 2 = CHCH 3 ) and propene-d 6 (CD 2 =CDCD 3 ) have been investigated, employing gas chromatography, mass spectroscopy, and flame ionization (GC/MS/FID) detection methods. The yields of methane as well as butadiene relative to ethane show considerable variations when propene-h 6 or propene-d 6 are photolyzed. This suggests significant variances in the relative importance of primary photolytic processes and/or secondary radical reactions, occurring subsequent to the photolysis. Theoretical calculations suggest the potential occurrence of an intramolecular dissociation through a mechanism involving vinylidene formation, accompanied by an ethylenic H-migration through the π-orbitals. This process affects the final yields of methane-h 4 versus methane-d 4 with respect to other products. The product yields from previous studies of the 193 nm photolysis of methyl vinyl ketone-h 6 and -d 6 (CH 2 =CHCOCH 3 , CD 2 =CDCOCD 3 ), alternative precursors for generating methyl and vinyl radicals, are compared with the current results for propene.