吡啶鎓取代基效应的从头算研究

A QUANTUM CHEMICAL STUDY ON SUBSTITUTE EFFECTS OF PYRIDINIUM

为寻找取代基效应与吡啶电子结构的关系 ,以吡啶钅翁—水复合体为模型 ,应用从头算 6-31G 基函数计算了 4 3个包括邻、间、对位三组吡啶钅翁化合物的电子结构 .结果得到 :( 1)取代基与吡啶环连接的原子的净电荷Qx1可描述取代基的共轭效应 ;( 2 )与邻、间位的取代基相邻的H原子净电荷 ,与对位取代吡啶N原子相邻的H原子净电荷可描述诱导 /场效应 ;( 3)

To study the relationships between substitute effects and electronic structures of pyridines, the calculations at ab initio 6-31G * level were performed for 43 substituted pyridinium-H 2O complexes which include three groups such as otho-,meta-,and para- substituted pyridiniums The results show the following: (1) resonance effects respond well to the net charge at the atom of substitute connected to pyridine ring; (2) inductive effects for otho-, meta- substituted pyridinums respond well to the net charge at the hydrogen adjacent to substitute, and inductive effects for para- substituted pyridines respond to the net charge at the hydrogen adjacent to N atom; (3) these quantum chemical indexes can be used to describe the influence of substitute effects on acidness of substituted pyridinium. The results are close to that which were obtained by DSP method.