1970 Volume 27 Issue 304 Pages 530-536
The reactions of hydroxymethylated 2-methoxy-4, 6-diamino-s-triazines (MMT) molecules in an acidic aqueous solution were studied kinetically. The average molar number of formaldehyde (F) combined (n) of MMT was 1.49 (Sample I) and 1.53 (Sample II), respectively. The reaction consisted of both the dissociation reaction of methylol groups and the condensation (methylene bond formation) reaction of methylol with amino groups. From the previous paper, however, as the dissociation reaction might be negligibly small compared with the condensation reaction in the initial stage of the reaction, the reaction was carried out in the range where the dissociation reaction might be negligible.
The condensation reaction obeyed the second order reaction untill ca. 12.7% of na (the initial concentration of methylol groups, a: the initial concentration of MMT (mol/l) for Sample I and 11.5% for Sample II had reacted.
The maximum value (kmax) of the rate constant (k) was obtained at [H3O+] =[H2O) /K1 (K1: the equilibrium constant of the reaction between MMT and acid)], and k was proportional to [H3O+] in a certanin range of pH where K1[H3O+]/[H2O]<<1 was maintained. In the case of the reaction where na and the concentration of added HCl were constant, kmax and k increased with the increase of “n”. These results were in agreement with those of the previous paper.
The activation energy (E) caluculated for the reaction of Sample II was 17.7kcal/mol, and it was approximately equal to E for the reaction of MMT having “n”=0.889-1.185.
