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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。
At the RHF / 6-31G level, the ground state proton transfer reactions of 5-hydroxyisoxazole trihydrate (HIO · 3H2O) and its 3-substituted derivatives were investigated. The geometric configurations and vibrational frequencies of HIO · 3H2O and other hydrated derivatives and proton tautomers were optimized and calculated. The transition state of proton transfer process was obtained by QTS2 method. According to the statistical thermodynamics principle and the transition state theory, the thermodynamic and kinetic properties of the interconversion of proton tautomers in this system were also studied. The calculated results show that the alcoholic structure of the electron-withdrawing substituent is more stable than that of the ketonic structure and the reaction rate is faster in the iso-azole compounds studied. The ketonic structure of the electron-donating substituent is more stable than the alcohol structure, Proton transfer energy barrier higher. This study is of great importance in the selection of appropriate derivatives of 5-hydroxyisoxazole for drug synthesis intermediates and substituents on proton transfer.