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.