Laser photolysis of 2-propanone, 2-butanone, 3-pentanone and 3-buten-2-one in the gas phase

Abstract

Abstract Low fluence (25 mJ.cm−2) and high fluence (180 mJ.cm−2) ArF laser (193.3 nm) photolysis of R1C(O)R2, (R1, R2 = CH3, C2H5, C2H3) afford carbon monoxide and hydrocarbons which are in the former case mostly R1-R2 alkanes and in the latter case R1-R2 alkanes along with methane, ethene and ethyne. The effect of excess of helium and hydrogen suggests that the products preferred at the high-fluence result from reactions of hot CH3· radicals, and disproportionations of C2H5· and cross disproportionation of CH3· radicals. No effect of radical scavenging [2H4]germane on the course of the low-fluence photolysis is judged to reflect high energy content of R1 and R2 radicals.