Réactions de condensation de formaldéhyde et d'urée

The condensation reaction of urea and formaldehyde was studied in a molar ratio 1:1 and 1:2 of both components; the reaction always proceeds by a second‐order mechanism. These reactions were compared and found analogous to the condensations of pure mono‐ and dimethylolurea. In neutral medium, by measuring at 65, 75, and 85° the value obtained for the energy of activation was 21 kcal./mole for both reactions; the 1:2 ratio‐condensation reaction is nevertheless three times slower than the 1:1 condensation. In acidic medium, a pure acid catalytic effect was found to be true, and the rates of the reaction between pH 3 and pH 5 were proportional to the hydrogen‐ion concentration; the activation energy was evaluated at about 8–10 kcal. for the acidic condensation reaction. At higher pH values, both reactions, thermal and acid‐catalytic, occur together, and the exponent to the hydrogen‐ion concentration in the expression of the rate of condensation appears to be smaller than unity. Analytical determinations of the condensation products are given and a likely kinetic scheme for the reaction is indicated.