Ion pair formation in the addition of protic reagents to alkynes

Abstract

The reaction of oct-4-yne with 20% trifluoroacetic acid and a variety of relatively weak nucleophiles in methylene chloride was found to produce a mixture of anion incorporated and solvent incorporated products. The rates of these reactions with a range of salt concentrations were found to be proportional to the rates of reaction of simple alkenes under similar conditions. The results are explained by the formation of an intermediate ion pair in contrast to the reactions of alkynes with bromide or iodide which proceeded by a concerted mechanism.