The reaction of phenol with formaldehyde: II. The ratio of ortho‐ and para‐hydroxymethylphenol in the base‐catalyzed hydroxymethylation of phenol.

A kinetic study of the first step in the reaction of phenol and formaldehyde, the formation of ortho‐ and para‐hydroxymethylphenol, is described. It is found that when using NaOH or KOH as a catalyst under weakly alkaline conditions (pH = 8.5‐10.5) at 30° C, the para‐position in the phenolic nucleus is nearly twice as reactive as the ortho‐position (the ortho/para ratio being 1.10). Interesting effects are observed in more strongly alkaline media (pH = 10.5‐13.5), inter alia a sharp decrease in the ortho/para ratio with increasing value of pH. When other hydroxides are used, an increasing value of the ortho/para ratio is found with the hydroxides of K, Na, Li, Ba, Sr, Ca and Mg, respectively. Probably chelate formation occurs in the transition state for ortho substitution.