Studies on formaldehyde resins, 25. Kinetic study on the hydroxymethylation of melamine by means of HPLC

The kinetics of hydroxymethylation of melamine (2,4,6-triamino-1,3,5-triazine) with formaldehyde to form N-(hydroxymethyl)melamine (2,4-diamino-6-hydroxymethylamino-1,3,5-triazine) was investigated in aqueous hydrogen phosphate/phosphate buffer solutions in the range of pH 10,51 to 12,20 at 20°C, determining unreacted melamine by means of HPLC. As a result, this reaction is subject to a general base catalysis, and the second order rate constant k is expressed by k = k′ + k_A ? [A^?] + k[A^?]²/[HA] (or k [A^?][OH^?]), where HA and A^? denote acid and basic constituents of the buffer, and k′ is the rate constant in unbuffered media. This rate equation is compared with those reported previously.