Kinetics and mechanism of the alkali‐catalysed addition of formaldehyde to dihydroxydiphenyl methanes

The kinetics of the alkali‐catalysed addition of formaldehyde to dihydroxydiphenyl methanes (DPMs) has been studied by quantitative paper chromatography. The order of reactivity of the three DPMs is found to be o.p′‐ > p.p′‐ > o.o′‐DPM. The low reactivity of o.o′‐DPM is explained on the basis of formation of a chelate ring in its singly ionised form, resulting in the fixation of the negative charge on the O. Equimolecular quantities of p.p′‐DPM and formaldehyde (concentrations 0.04 M) react in presence of NaOH (0.006 M) to give 3‐methylol‐4.4′‐DPM. Under similar conditions o.p′‐DPM gave 3‐methylol‐2.4′‐DPM, 5‐methylol‐2.4′‐DPM and 3‐methylol‐2′.4‐DPM and o.o′‐DPM gave 3‐methylol‐2.2′‐DPM and 5‐methylol‐2.2′‐DPM. The individual rate of formation of each of the products is determined. These rates are compared with those of other reactions in the phenol‐formaldehyde reaction, and their relative importance in the overall reaction is discussed.