5-甲基胞嘧啶互变异构体热力学稳定性及质子迁移机理的理论研究  

Theoretical Study on Thermodynamic Stability of Tautomers and Proton Transfer Isomerization of 5-Methylcytosine

作　　者：靳玲侠[1] 杨佳红[1] 李琛[1] 闵锁田[1] 魏雅雯[2] 

机构地区：[1]陕西理工学院化学与环境科学学院陕西省催化基础与应用重点实验室,陕西汉中723001 [2]长安大学出版科学研究所,陕西西安710064

出　　处：《化工技术与开发》2016年第6期1-5,65,共6页Technology & Development of Chemical Industry

基　　金：中央高校基金资助项目(310850160322);陕西省教育厅专项科研基金项目(16JK1153);陕西理工学院科研基金资助项目资助(SLGQD14-10;SLGKYQD2-13)

摘　　要：采用密度泛函理论,在B3LYP/6-31++G//B3LYP/6-31G基组水平上对5-甲基胞嘧啶互变异构体及质子转移机理进行了研究,获得了10种5-甲基胞嘧啶互变异构体及12个异构化过渡态,并获得了互变异构过程的反应焓、活化能、活化吉布斯自由能和质子转移反应的速率常数等性质。计算结果表明,5-甲基胞嘧啶各互变异构体的相对热力学稳定性为:M1>M3>M4>M5>M6>M2>M7>M8>M9>M10。其中氨-酮式结构M1能量最低,稳定性最高;亚氨-烯醇式结构M10相对能量最高,稳定性最低。在5-甲基胞嘧啶的异构化过程中,部分异构体之间可以相互转化,其中键旋转较质子迁移所需活化能较低,反应较易实现。由氨酮式M1通过分子内质子迁移及键旋转异构转化共有6条反应通道,其主通道(5)速控步骤的活化能为163.81 k J·mol^(-1),反应较难实现。The stability and tautomerism mechanisms of 5-methylcytosine had been investigated by the B3LYP/6-31++G//B3LYP/6-31G level of theory. 10 tautomers and 12 transition states were located and a variety of possible reaction pathways were probed. The reaction enthalpies, activation energies, activation free energies and the rate constants of tautomerism were also obtained. The results showed that the order of the thermodynamic stability of tautomers was:M1>M3>M4>M5>M6>M2>M7>M8>M9>M10. The amino-keto form was the predominant isomer. 6 reaction pathways from amino-keto to other isomers were found by intramolecular proton transfer and tautomerisms process. The main pathway (5) associated with the activation energy was 163.8 kJ/mol, which was of no advantage to the reaction.

关 键 词：5-甲基胞嘧啶 密度泛函理论方法 互变异构 过渡态 

分 类 号：O642[理学—物理化学]