中文摘要：

用密度泛函理论（DFT）B3LYP方法，在6-311＋G^＊基组下，对3-羟基哒嗪及其CH3，NO2和Cl取代衍生物分子醇式和酮式结构互变异构化反应进行了研究，优化化合物的几何构型，寻找反应的过渡态，通过振动分析和内禀反应坐标（IRC）分析加以证实，计算了反应的活化能．结果表明，3（2H）-哒嗪酮及其带取代基的衍生物不论是单体，还是相对应的二聚体，比其相对应的异构体能量低，表明在通常情况下是以3（2H）-哒嗪酮及其衍生物形式稳定存在的，这与前人通过实验数据对3-羟基哒嗪互变异构体的比率进行预测的结果是一致的．根据计算结果讨论了异构化反应的机理．

英文摘要：

Density functional theory B3LYP method at the 6-311 ＋G^＊ basis set was used to investigate the mechanism of tautomerism between enol form and keto form of 3-hydropyridazine as well as its methyl, nitro or chloro derivatives, with the geometric structures of reactants, transition states and products optimized completely. In addition, the transition states have been explored and proved by vibration analysis and intrinsic reaction coordination analysis, and meanwhile, the total energies and reaction activation energies have been calculated. The results showed that the most stable isomers are compounds with the structure of 2-hydropyridazin-3-one or its derivatives compared with the other corresponding isomers, which was in good agreement with the previous reports that predicted the ratio of isomers by experimental data. The mechanism of the isomerization was discussed on the basis of the theoretical values.