Formaldehyde equilibria: Their effect on the kinetics of the reaction with phenol

The kinetics of the base catalyzed hydroxymethylation of phenol by aqueous formaldehyde are influenced strongly by the equilibria among the hydrated forms of formaldehyde, and among the hydrates and the alcoholic function of the products. Apparent peculiarities in the kinetics of the system and seemingly anomalous solvent effects are shown to be due to erroneous formulation of the previously accepted rate expression. The correct expression is: Rate = k[Pi−] [F]m, where Pi− is phenoxide ion, F is unreacted formaldehyde, and m is the fraction of formaldehyde in the form of monomeric hydrate. Formaldehyde tied up in equilibria as αω‐poly(oxymethylene) diols, and hemiformals of the hydroxymethylphenols, constitutes a potential source of formaldehyde and is detected by the usual analytical procedures, but does not contribute to the rate of the hydroxymethylation reaction.