分别利用密度泛函、从头算分子轨道方法及半经验分子轨道AM 1法对 2 溴乙酸气相热消除反应的机理进行了理论研究 .结果表明 ,虽然用三种不同的方法得到的结果有一定差异 (如反应势能面上各驻点的几何构型、反应的活化能 ) ,但研究得到的反应机理是一致的 ,即反应分两步进行 .其中 ,具有五元环过渡态的第一步反应为速控步骤 ,与实验工作者所建议的机理相符 . The mechanism of heat elimination reaction of 2-bromoacetic acid gas was studied theoretically by means of density functional theory, ab initio molecular orbital method and semi-empirical molecular orbital AM 1 method. The results show that although the results obtained by three different methods are different (Such as the geometry of the stagnation point on the potential surface of the reaction, the activation energy of the reaction), but the reaction mechanism obtained is consistent, that is, the reaction proceeds in two steps, of which the first reaction with the five-membered ring transition state For speed control steps, consistent with the experimental workers suggested mechanism.