Pulsed Infrared Laser Inducement of Multiple Reaction Channels in Ethyl 3-Cyclohexene-1-carboxylate

Article abstract of DOI:10.1021/j100226a010

The pulsed CO2 laser-induced reaction of ethyl 3-cyclohexenecarboxylate, a large organic ester with two reaction channels differing by ca. 13 kcal mol^-1 in threshold energies, was studied over the 0.02-0.20-torr pressure range.The absorbed laser energy and the reaction probabilities were measured as functions of laser energy, laser intensity, and added bath gas.The reaction product ratio was very dependent on the incident laser energy but almost independent of the laser pulse duration (intensity) at constant fluence.The dependence of the product ratio on the absorbed energy was satisfactorily explained for low fractional reaction by a postpulse model using RRKM rate constants and a broad distribution function (simulated as a Boltzmann distribution) with mean energy equal to the absorbed laser energy.In addition to implying that the internal energy is randomly distributed prior to reaction, the model implies that all, or nearly all, of the molecules absorb the laser energy.Addition of bath gas significantly lowered the reaction probability but had only a minor influence on the product partitioning ratio; these results were also interpreted satisfactorily by the model calculations.The laser-driven secondary reaction of the ethyl acrilate product, even for single-pulse experiments, is important.