Conclusions It was not possible to measure the rate of hydrogen abstraction from either allene or 1, 3-butadiene because of both the larger rate of the addition reaction and the weaker decrease in the rate of the addition reaction in comparison with the reaction of ethylene. However, an upper limit of about twice the predicted rate for H abstraction from ethylene can be inferred from these data. The reactions of the three olefins ethylene, 1, 3- ...