Reactions of alkyl vinyl ethers catalysed by triethyloxonium hexachloroantimonate and its decomposition products, in particular antimony pentachloride
i.r. spectroscopy has been used to study the rates of disappearance of vinyl double bonds from systems containing isobutyl, phenyl, or 2-chloroethyl vinyl ethers and triethyloxonium hexachloroantimonate in dichloromethane. A fast primary reaction giving limited conversion of the alkyl vinyl ethers to oligomeric products was ascribed to catalysis by antimony pentachloride formed by the spontaneous decomposition of triethyloxonium hexachloroantimonate. Fast but limited conversion also occurred when antimony pentachloride was added to solutions containing alkyl vinyl ethers. Electronic spectra and conductivities of reacting systems and i.r., 1H n.m.r., and mass spectra of reaction products were recorded. The implications of the results with respect to the initiation, propagation, transfer, and termination steps of the overall reaction are discussed. A slow secondary reaction of alkyl vinyl ethers initiated by triethyfoxonium hexachloroantimonate was in part due to the continued generation of antimony pentachloride by decomposition of catalyst but also contained a contribution arising from catalysis by triethyloxonium ions.