Nonequilibrium Unimolecular Decomposition of Ethylene

Some of the experimental data in the literature on the nonequilibrium decomposition of ethylene have been examined in the light of calculations using a simple Rice–Ramsperger–Kassel–Marcus treatment. An activation energy of approximately 80 kcal mole−1 is indicated for the molecular elimination of hydrogen. Of the energy available to the products of the initial processes by which excited ethylenes are formed, the fraction retained by ethylene does not appear to be constant, as was previously concluded using the classical RRK theory of unimolecular reactions. In the case of ethylene produced in the photolysis of 3-methyldiazirine, an alternative explanation for the limiting yield of acetylene at low pressure is offered, based upon an arbitrary energy distribution selected to match the experimental data.