乙腈及其氯代物水解反应机理的理论研究

A theoretical study of the reaction mechanism of acetonitrile and chloride hydrolysis

采用密度泛函方法研究了乙腈和氯代乙腈的水解反应机理.在B3LYP/6-31++G(d,p)水平上优化了水解反应途径中的反应物、过渡态、中间体及产物的几何构型.在乙腈的水解途径中首先形成一个四元环的过渡态,对应水分子中的O原子进攻乙腈上的C原子,同时水分子上的一个H原子转移到乙腈的N原子上,形成不稳定的烯醇中间体.该中间体可以异构化为更稳定的乙酰胺,乙酰胺与另一个水分子作用,最终水解为乙酸和氨气.氯代乙腈的水解反应机理和乙腈基本一致,但其反应活化能垒比乙腈低,产物为氯代乙酸和氨气.

Density functional theory was used to study the hydrolysis mechanism of acetonitrile and chloroacetonitrile. The geometries of reactants, transition states, intermediates and products in the hydrolysis reactions were optimized at B3LYP/6 -31 ＋ ＋ G（ d, p） level. In the hydrolysis of acetonitrile, a four -membered ring transition state forms first, corresponding to the O atom of the water molecule attacking the C atom of acetonitrile, and a H atorn of the water molecule transfers to the N atom of acetonitrile to form an unstable enol intermediate. The intermediate can be isomerized to a more stable acetamide, and then the acetamide reacts with another water molecule. The final products are acetic acid and ammonia. The mechanism for the hydrolysis of chloroacetonitrile is nearly the same as that of acetonitrile, but its activation barrier is lower than that of aeetonitrile. The products are chloroacetic acid and ammonia.