Theoretical Study on the Reaction of Thymine with Iodomehane in the Water Phase

• 来源期刊: 结构化学
• 学科: 工学
• 关键词: 反应机制 胸腺嘧啶 水相法 计算结果 电子表格 甲基化剂 连续模型 四氯化碳
• 年，卷（期）: 2012,（2）
• 页码范围: 292-298
• 页数: 7页
• 分类号: TQ536.1|TS255.44
• 语种: 英文

摘要

The reaction mechanisms of carcinogenic methylating agent iodomethane （MeI） with keto and enol tautomers of thymine （K- and E-thymine） were studied by using the B3LYP/6-311＋G （d, p） method in water phase. The solvent effects were examined using the polarizable continuum model （PCM）. Specifically, PCM single-point calculations at the same level of theory were performed in acetone and CCl4 that represent a range in nonpolarity. The calculated results show that the reaction of K-thymine with MeI is a two-step mechanism, whereas that of E-thymine is a one-step mechanism. Our calculations reveal that K-thymine is appreciably more stable than the enol form in the water phase or in the two solvents. The K- and E-form reaction barriers are 135.6 and 222.1 kJ/mol, respectively in water phase. These findings indicate that the reactions mentioned above could not occur efficiently in biological media in the absence of catalyst. Our conclusions are in agreement with the previous studies on the reactions of guanine with methyl chloride and methyl bromide.