3-羰基吡唑质子转移过程的理论研究  

Theoretical Study on the Proton Transfer in 3-Aldehyde Pyrazole

作　　者：陈媛丽[1] 李宝宗[1] 国永敏[1] 

机构地区：[1]苏州大学独墅湖校区化学化工学院,江苏苏州215123

出　　处：《化学研究》2008年第1期43-46,51,共5页Chemical Research

基　　金：国家自然科学基金资助项目(20673075);江苏高校国家级有机化学重点学科培育点经费资助项目

摘　　要：采用密度泛函B3LYP/6-311G**方法,对3-羰基吡唑几何构型进行了全自由度优化,获得了它们的几何结构和电子结构.计算并考察了3-羰基吡唑的两种构象即syn和anti构象的稳定性以及3-羰基吡唑进行结构互变的质子转移过程的四种可能途径:(a)分子内质子转移;(b)水助质子转移;(c)同种二聚体双质子转移;(d)异种二聚体双质子转移.计算结果表明3-羰基吡唑的syn构象中N2-H型的稳定性大于N1-H型,进行质子转移时途径(c)所需要的活化能最小(52.78 kJ/mol),途径(a)所需要的活化能最大(200.59 kJ/mol);3-羰基吡唑的an-ti构象中N1-H型的稳定性大于N2-H型,进行质子转移时途径(d)所需要的活化能最小(61.09 kJ/mol),途径(a)所需要的活化能最大(204.15 kJ/mol).The molecular structures of 3-aldehyde-pyrazole tautomers with full geometry optimization were calculated by the B3LYP method at the 6-311 G＊ ＊ level. The geometry and electronic structures of the tautomers of 3-aldehyde pyrazole and their transition states were obtained. The four possible reaction pathways were investigated including： （a） intramolecular proton transfer; （b） water-assisted intermolecular transfer; （c） isomerization by double-proton transfer in the dimer and （d） intermolecular proton transfer via the complex formed. The results of the calculation indicated that the N1-H form of the anti conformer was more stable than that of the N2-H form, and the process in （d） has the lowest activation energy（61.09 kJ/mol）, whereas the N2-H form of the syn conformer is more stable than that of the N1-H form and the process in （c） has the lowest activation energy（52.78 kJ/mol）. It was likely that the hydrogen bonds formed in the complexes played an important role in proton transfer processes in the latter three reaction pathways.

关 键 词：3-羰基吡唑 密度泛函理论 过渡态 互变异构体 质子转移 

分 类 号：O641.12[理学—物理化学]