METHANE LOSS IN THE INFRARED MULTIPHOTON DISSOCIATION OF ACETIC-ACID

The infrared multiphoton dissociation (IRMPD) of acetic acid was studi ed by photofragment translational spectroscopy. Carbon dioxide and met hane were observed for the first time as products from dissociation un der collisionless conditions. The product translational energy distrib ution for this channel peaks well away from zero, which supports a fou r-center transition state. A previously observed channel, resulting in the formation of ketene and water, was verified. The average translat ional energy release for the former channel was measured to be 26.4 kc al/mol, and a value of 18.6 +/- 2 kcal/mol was obtained for the dehydr ation channel. With a laser fluence of 12 J/cm(2), decarboxylation acc ounts for roughly 35% of the total dissociation yield.