Publication costs assisted by the Petroleum Research Fund Ethyl radicals, formed by photolysis of azoethane, react with nitric oxide by successive addition to yield nitrosoethane and triethylhydroxylamine. Nitrosoethane is the sole product until the nitric oxide concentration has been reduced to very low levels, at which time the addition reaction to form the triethylhydroxylamine takes place in competition with the combination and disproportionation reactions of ethyl radicals. In the absence of ethyl radicals, or in experiments with initial nitric oxide concentrations above 6%, the dimerization of nitrosoethane is observed. Kinetic analysis of the data subsequent to depletion of nitric oxide affords an evaluation of specific reaction rates for the addition of ethyl radicals to monomeric nitrosoethane and for the reversible dimerization of monomeric nitrosoethane. The ionization potential of monomeric nitrosoethane was determined from a study of the photolytic growth rate dependence of CdT-NOon electron energy.

1335were the dominant mechanism.23 This prediction is related to the observation reported in the single-pulse shock tube study of the Hz + Dz exchange that the rate depended more strongly on the concentration of Dz than on H2.21,24 In the temperature range 1050-1200"K, the rate of Dz with CzNz was found to be faster than that of HZ with CzN2 although the rate decreased with increasing tempera t~r e .~~ According to VEC, the important species is CzNz" and not H2U or D2U. Consequently, there should be a decrease in the rate constant as expected from the normal isotope effect when D:l rather than Hz is reacting with CzN2. The magnitude of the isotope effect, A D J A H~, calculated from collision theory, is listed below for both atomic and VEC mechanisms. H,, D, + CN -HCN, DCN + H, D 0.73 (15) H, D + C2N2-HCN, DCN + CN 0.715 (16) Darryl Olivier who helped maintain the equipment, and Professors Robert Flurry and Peter Politzer for fruitful discussions. We appreciate very much a critical review of the manuscript by Professor S. H. Bauer. Publication costs assisted by The U. S. Atomic Energy Commission and The Petroleum Research FundThe photolysis of hexafluoroazomethane in the visible fluoromethyl radicals at near room temperature. The products of the photolysis are nitrogen, hexafluoroethane, perfluorotetramethylhydrazine, and perfluorohexamethyl-and near-ultraviolet regions of the spectrum has been well studiedz-? and often used8-12 as a convenient source of tri-