The reaction of 1, 1-diphenylethylene (DPE) and CF3SO3H was studied in dichloroethane at 30ŶC by stopped-flow/rapid-scan spectroscopy. The formation of the monomer cation was a fairly clean second-order process with the rate constant of 3400 M蜢1 s蜢1. The absence of the dimer cation in the early stage of the reaction was confirmed by rapid quenching (CH3ONa in CH3OH) of the reaction mixture. The monomer cation was slowly converted into a cyclic dimer product (indanic dimer) in a few hours. Linear dimers could not be detected even after prolonged reaction. These results are in sharp contrast with those of Evans and coworkers who observed the exclusive formation of the linear dimer (in benzene with a variety of acidic catalysts). The 舠autosolvated舡 dimer cation proposed by Sigwalt and coworkers could not be observed in our experiments.
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