AbstractThe 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.
摘要 研究了脲和甲醛在两种成分的摩尔比为 1:1 和 1:2 时的缩合反应。对这些反应进行了比较，发现它们与纯的一缩脲和二缩脲的缩合反应类似。在中性介质中，通过在 65°、75° 和 85°温度下测量，两种反应的活化能值均为 21 千卡/摩尔；然而，1:2 比例缩合反应比 1:1 缩合反应慢三倍。在酸性介质中，发现纯酸催化作用是真实的，pH 值为 3 至 5 之间的反应速率与氢离子浓度成正比；酸性缩合反应的活化能约为 8-10 千卡。在较高的 pH 值下，热反应和酸催化反应同时发生，缩合速率表达式中的氢离子浓度指数似乎小于 1。给出了缩合产物的分析测定值，并指出了该反应可能的动力学方案。
