甲苯定向硝化的理论研究  

A Theoretical Study on Selectivity for Nitration of Toluene with Nitronium

作　　者：陈丽涛[1] 肖鹤鸣[1] 肖继军[1] 

机构地区：[1]南京理工大学化学系

出　　处：《化学学报》2003年第8期1169-1174,共6页Acta Chimica Sinica

基　　金：国家自然科学基金 (No.1 0 1 760 1 2 );国防基础研究基金资助项目

摘　　要：运用密度泛函理论 (DFT)B3LYP方法 ,在 6 3 1G 基组水平上 ,全优化计算了硝酰阳离子NO+ 2 对苯和从o ,m ,p 位进攻甲苯的亲电取代硝化反应 .求得 4条反应途径上包括反应物、过渡态和Wheland中间体共 (4× 3 ) 12个反应驻点σ络合物的分子几何、电子结构、能量和IR光谱等性质 ,阐明了反应中无同位素效应的实验事实 ,求得各反应途径的活化能排序 :p >o >PhH >m 和σ络合物 (R ,TS或INT)的相对稳定化能排序 :p ArCH3 NO+ 2 >o ArCH3 NO+ 2 >m ArCH3 NO+ 2 >PhH NO+ 2 ,从而阐明了甲基对苯环致活 (或致钝 )以及增加甲苯硝化络合物稳定性的双重功能 。Four nitration trajectories of benzene and toluene with nitronium ion have been calculated. Totally twelve stationary points including four transition states were successfully located for the first time by using hybrid DFT procedure B3LYP with 6-31G* * without any assumption. Mechanistic studies on structures, atomic charges, energies and IR spectra for stationary points are presented to reveal the dual roles of incoming methyl group, which impacts on positional selectivity of electrophilic aromatic nitration. The order in activation energy for concerned nitration reactions was found as p- > o- > PhH > m-. Another order in isodesmic energy showing the relative stability of EDA complexes was derived as p-ArCH3-NO2+ > o-ArCH3-NO2+ > m-ArCH3-NO2+ > PhH-NO2+. In addition, absence of kinetic isotope effect in most electrophilic aromatic substitutions could also be suggested by our results.

关 键 词：甲苯 定向硝化 理论研究 密度泛涵理论 苯 构型 IR谱 

分 类 号：O621.2[理学—有机化学]