The SN2′ mechanism. Chloride ion-catalysed isomerization of α- and γ-methylallyl chloride

Abstract

The chloride ion-catalysed isomerization of α- and γ-methylallyl chloride in acetonitrile has been assigned an S_N2′ mechanism and the isotope-exchange reactions with labelled chloride ions have been assigned S_N2 mechanisms. This reaction system provides a second example of isomeric rearrangement by the S_N2′ mechanism and quantitative data for comparison with the data for the bromide ion-catalysed isomerization and isotope-exchange reactions of α- and γ-methylallyl bromide in acetone.

The two systems are closely similar in behaviour, the most significant difference being the presence of a minor concurrent elimination reaction accompanying the isomerization reaction of α-methylallyl chloride.