A Hydrogen-Roaming Pathway for Formation of Methane in the 193 nm Photodissociation of Propene; CH3CH=CH2 and CD3CD=CD2

Published

October 16, 2008

Author(s)

Yi-Lei Zhao, Allan H. Laufer, Joshua Halpern, Askar Fahr

Abstract

Photodissociation channels and the final product yields from the 193 nm photolysis of propene-h6 (CH2=CHCH3) and propene-d6 (CD2=CDCD3) 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-h6 or propene-d6 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 intra-molecular dissociation through a H-roaming mechanism, involving the ethylenic H- (or D-) atom that likely interacts through the p-orbitals with the methyl group of the precursor to form methane. This process affects the final yields of methane-h4 versus methane-d4 with respect to other products.The product yields from previous studies of the 193 nm photolysis of methyl vinyl ketone-h6 and d6 (CH2=CHCOCH3 , CD2=CDCOCD3), alternate precursors for generating methyl and vinyl radicals are compared with the current results for propene.

Citation

Journal of Physical Chemistry A

Pub Type

Journals

Keywords

effects, isotope, mechanism, photodissociation, propene

Citation

Zhao, Y. , Laufer, A. , Halpern, J. and Fahr, A. (2008), A Hydrogen-Roaming Pathway for Formation of Methane in the 193 nm Photodissociation of Propene; CH₃CH=CH₂ and CD₃CD=CD₂, Journal of Physical Chemistry A (Accessed October 12, 2025)