The Mechanism of the Alkaline Fusion of Benzenesulfonic Acid.

Benzenesulfonic acid-1-14C was fused with potassium hydroxide at 320—350°C for five minutes. The phenol obtained was then degraded as usual, and the distribution of carbon-14 in the phenol was determined. Practically all the 14C activity was found at the 1 position of the phenol, which means that there is no migration of the 14C originally labeled at the position 1 or the benzenesulfonic acid. Benzenesulfonic acid was also treated with potassium hydroxide enriched with 18O. The resulting phenol was found to be incorporated, with the same concentration of 18O as that of the 18O enriched water used. The results show that the mechanism of the reaction is of a simple SN2 type and not of the elimination-addition type involving the benzyne intermediate, while there was no oxygen migration in the reaction.