Some studies of base-catalysed isomerisations in the hexyne-hexadiene system

Abstract

The isomerisations of 2-hexyne, 3-hexyne and 2,3-hexadiene were repeated in order to investigate more extensively the possibility of formation of conjugated dienes during isomerisations in a solution of sodium amide in liquid ammonia. All the experimental evidence showed that no conjugated dienes were formed. 2,4-Hexadiene was found to be stable in sodium amide/liquid ammonia solution, whereas 1,3-hexadiene isomerised to 2,4,-hexadiene in the same base system. The isomerisations of 1-hexyne, 2-hexyne, 3-hexyne, 1,2-hexadiene and 2,3-hexadiene were studied in a solution of potassium t-butoxide in t-butanol. Preliminary results are in accord with a stepwise acetylene-allene-acetylene path. The rates of isomerisations appear to be pseudo first order in the starting materials under the experimental conditions. The influence of solvent on rate of reaction is briefly discussed.