取代基对水合5-羟基异噁唑质子转移影响的理论研究  

Theoretical study the substituent effect on proton transfer for the hydrated 5-hydoxyisoxazole

作　　者：易平贵[1] 梁永宏[1] 曹晨忠[1] 

机构地区：[1]湖南科技大学化学化工学院,湖南湘潭411201

出　　处：《计算机与应用化学》2006年第4期313-316,共4页Computers and Applied Chemistry

基　　金：国家自然科学基金(20173050);国家科技攻关计划专题子项(2004BA308A22-1);湖南省自然利学基金(04JIY40010)资助项目

摘　　要：在RHF／6-31G水平上,考察了三水合5-羟基异嗯唑(HIO·3H2O)及其3-位取代衍生物的基态质子转移反应。优化并计算了HIO·3H2O及其它水合衍生物和质子互变异构体的几何构型和振动频率分析,并用QTS2方法获得质子转移过程的过渡态。进一步根据统计热力学原理及过渡态理论,研究了该体系质子互变异构体之间相互转化的热力学及动力学性质。计算结果表明,在所研究的异(?)唑化合物中,吸电子取代基的醇式结构比酮式结构稳定,反应的速率较快;而供电子取代基的酮式比醇式结构稳定,质子转移的能垒较高。该研究对选择适当5-羟基异嗯唑的衍生物作药物合成中间体及取代基对质子转移的影响方面具有重要意义。Theoretical investigation on intermolecular proton transfer of the hydrated 5-hydroxyisoxazole （HIO·3H2O） and its derivatives by hydroxide wire was performed. The molecular geometries of HIO·3H2O and its derivatives were optimized and the viberation analysis were carried out at the HF/6-31G＊ level considering the model isolated. Transition states for the tautomeric processes were located by using the Synchronous Transit Guided Quasi-Newton （STQN） methods. The thermodynamic and kinetic parameters of the proton transfer reactions were also studied based on the calculated results statistical mechanics and transition state theory. The predicted results showed that the enol form is more stable than its keto form for the electron drawing substituents and its reaction barrier is lower, however, the keto form is stable for the electron donating substituents and its reaction barrier is higher than that of HIO·3H2O. This researeh will facilitate to choose the proper derivatives of 5-hydroxyisoxazole as a mediate to synthesize the drug, and it is important to study the subsituent effect on the proton transfer.

关 键 词：ab INITIO 5-羟基异噁唑 质子转移 过渡态 互变异构 

分 类 号：O641.121[理学—物理化学]