3-羰基吡唑质子转移过程的理论研究.pdfVIP

第19卷第1期 化 学 研 究 V01．19 No．1 2008年3月 CHEMICAI RESEARCH Mar．2008 3-羰基吡唑质子转移过程的理论研究 陈媛丽，李宝宗 ，国永敏 (苏州大学独墅湖校区化学化工学院，江苏 苏州215123) 摘 要：采用密度泛函B3LYP／6—311G一方法，对3一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3一羰基吡唑的两种构象即syn和anti构象的稳定性以及3一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3一羰基吡唑的syn构象中N2一H型的稳定性大于N1一H型，进行质子转移时 途径(C)所需要的活化能最小(52．78 kJ／too1)，途径(a)所需要的活化能最大(200．59 kJ／mo1)；3 羰基吡唑的。 ti构象中Nl—H型的稳定性大于N2一H型，进行质子转移时途径(d)所需要的活化能最小(61．09 kJ／too1)，途径 (a)所需要的活化能最大(204．15 kJ／mo1)． 关键词：3一羰基吡唑；密度泛函理论；过渡态；互变异构体；质子转移 中图分类号：O 641．12 文献标识码：A 文章编号：1008—1011(2008)0l一0043—04 Theoretical Study on the Proton Transfer in 3-Aldehyde Pyrazole CHEN Yuan—li，LI Bao—zong ，GUO Yong—min (School Chemistry and Chemical Engineering，Suzhou University,Suzhou 215123，Jiangsu，China) Abstract：The molecular structures of 3-·aldehyde-·pyrazole tautomers with full geometry optimization were calculated by the B3 LYP method at the 6-3 1 1 G leve1．The geometry and electronic structures of the tautomers of 3-aldehyde pyrazole and their transition states were obtained．The four possible re— action pathways were investigated including：(a)intramolecular proton transfer；(b)water—assisted in— termolecular 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 N1一H form of the anti conformer was more stable than that of the N2一H form，and the process in(d)has the lowest activation energy(6 1．09 kJ／mo1)，whereas the N2一H form of the syn conformer i