Reactivity and structure of alkyl vinyl ethers. Part III. Kinetics and mechanism of dichlorocarbene addition reactions

Abstract

The reaction of a series of alkyl vinyl ethers (ROCHCH₂) with dichlorocarbene (generated by reaction of potassium t-butoxide with chloroform) has been studied. Products were characterised as the appropriate dichlorocyclopropyl ethers. Competition experiments showed that the relative rates of reaction varied for a series of alkyl groups (R) in the order t-butyl (2·43), isopropyl (1·56), ethyl (1·20), methyl (1·03), isobutyl (1·00), 2-chloroethyl (0·48). On this scale, cyclohexene had a relative rate of 0·94. The order of reactivity is approximately parallel with that observed previously for acid-catalysed hydrolysis and it is suggested that the transition state for the carbene reaction involves the oxygen atom directly.