J . Am. Chem. SOC.1983, 105, 5124-5729
5124
reactions. We were also able to show the C4H4+*cluster ion in acetylene is >90% cyclic isomer and the C4H4+-ion from methylene-2,3-dimethylcyclopropaneis 12 f 10% cyclic isomer. Also, the C4H4+*ion originating from the metastable reaction of benzene parent ion is 82 f 10% cyclic C4H4+-.Finally, it was possible to infer that linear C4H4+.reacts very much faster than cyclic C4H4+ewith acetylene. 2. The ion chemistry of I-C4H4+*reacting with acetylene was explored by using the tandem ICR. The total rate constant for reaction of 1-C4H4+*was measured to be (3 f 1.5) X cm3/s. The rate constant for the cyclic isomer with acetylene was immeasurably slow (
