Proton transfer reactions of C 2H 4[rad]+ : the bond energy D(C 2H 3−H)

Abstract

Reactions of C 2H 4 + with a series of molecules having different proton affinities were studied with a selected-ion flow tube in order to bracket the proton affinity (PA) of the C 2H 3 radical. Since the proton transfer reactions were studied only in the forward direction, the PA values were obtained from correlations between the efficiency of proton transfer and the overall reaction thermochemistry. Reactions with CH 3OH and CClH 2CN were particularly relevant and yielded PA(C 2H 3) = 182.2 ± 1 kcal mol −1 at 298K. A thermochemical cycle leads to the bond energy D 298(CH 2CHH) = 110.9 ± 1 kcal mol −1, in excellent agreement with recent data based on negative ion acidity experiments.