Kinetics and mechanism of the alkali catalysed condensation of <i>o</i>‐ and <i>p</i>‐methylol phenols by themselves and with phenol

Abstract

Abstract The kinetics of the alkali‐catalysed condensation of ortho and para methylol phenols, each by itself and with phenol has been studied under various experimental conditions with the help of quantitative paper chromatography. At low concentrations of the reactants and catalyst, the self‐condensation of saligenin gives mainly 3‐methylol 2′,4‐dihydroxy diphenyl methane (DPM) and that of p ‐methylol phenol 5‐methylol 2,4′‐DPM, the apparent first‐order rate constant at 80°C. and activation energy being 1.60ċ10 −5 sec −1 and 16.0 kcal./mole for the former and for the latter 1.67ċ10 −5 sec −1 and 17.3 kcal./mole However at higher concentrations, p ‐methylol phenol gives also p,p ′‐DPM, 2,4‐dimethylol phenol, and small amounts of 3‐methylol 4,4′‐DPM. When phenol and one of the methylol phenols are made to react, both the self‐condensation and the inter‐condensation take place, the former much more rapidly than the latter. A large excess of phenol is needed to suppress the self‐condensation. The apparent energies of activation for the formation of o,o ′‐, o,p ′‐ and p,p ′‐DPMs are 21.4, 18.7, and 17.0 kcal./mole respectively. Evidence is presented for the probable mode of formation of monomethylol dinuclear compounds in the alkali‐catalysed phenol‐formaldehyde reaction.