Relative Reactivities of Alkyl Chlorides under Friedel‐Crafts Conditions

Competition experiments have been performed to determine the relative reactivities of 23 alkyl chlorides toward allyltrimethylsilane in the presence of catalytic amounts of ZnCl 2 .The k rel scale spans over 11 orders of magnitude from 1‐adamantyl chloride (least reactive) to bis( p ‐methoxyphenyl)methyl chloride (most reactive compound). A fair correlation between the alkylating ability and the S N 1 reactivity in solvolysis reactions is found, thus providing a quantitative basis for our long‐standing working hypothesis that Lewis acid‐catalyzed additions of alkyl halides to CC multiple bonds only yield 1:1 products if the reactants ionize faster than the products. Trityl chlorides do not follow this correlation and are 10 5 times less reactive than predicted from their S N 1 reactivities.