15min:

BRAD ROWLAND AND WAYNE HESS, Battelle Pacific Northwest National Laboratories, PO Box 999, Richland, WA. 99352, Mail Stop K2-14.

Ultraviolet photolysis of condensed-phase acetyl chloride (CH₃COCl) produces ketene (H₂C=C=O) and HCl in a 1:1 dimer complex. The reaction mechanism sharply differs from the photodissociation of gas-phase molecules which produces chlorine and acetyl radical (CH₃CO) that further dissociates to CH₃ and CO. Two mechanisms of photodissociation of condensed-phase acetyl chloride have been proposed; concerted elimination and the caged abstraction. Thermodynamic analysis, polarized IR studies, and general spectroscopic observations of the photoproducts are used to show that the photodissociation of condensed acetyl chloride follows a concerted elimination mechanism.