2-氨基吡啶气相氟代反应的密度泛函理论研究

采用量子化学方法,运用密度泛函理论(DFT)B3LYP方法,在6-311G*基组水平上,以2-氨基吡啶为起始反应物,全优化计算了亚硝酰阳离子NO~+对2-氨基吡啶中氨基进攻的重氮化反应及氟硼酸根阴离子BF_4~-对吡啶重氮正离子进攻的席曼反应的机理,搜索到整个反应过程中的过渡态结构,得到了反应路径并通过IRC验证,并对各反应中间体、过渡态和产物进行分子几何构型优化、振动频率分析和标准热力学函数计算.通过计算,搜索到的过渡态均为环状结构,与配位插入反应类似,利于原子间化学键的断裂及新键的形成;通过热力学及动力学计算,重氮化-席曼反应是剧烈的放热反应,与实验结果相吻合.

The theoretical study on mechanism of gas phase fluorination of 2-aminopyridine

The mechanism of gas phase fluorination of 2-aminopyridine leading to 2-fluoropyridine was studied using the density functional theory (DFT) method at the B3LYP/6-311G* level. The pathways of both diazoreaction of 2-aminopyridine with nitrosyl cation (NO~+) and Schiemann reaction of diazo cation with fluoborate ion (BF_4~-) were calculated without any assumption. The geometrical parameters of transition states (TS) and intermediates (IM) were optimized. Intrinsic reaction coordinate (IRC) was also performed to obtain further credible features. Frequency analyses of all the stationary points were calculated at the same basis sets. The calculation results revealed that the transition states have ring structure, similar to coordinated-inserted reaction, which are propitious to the rupture and formation of chemical bonds. The reaction was proved to be an exothermic reaction by dynamic and thermodynamic which agrees with experimental results.