吡啶钅翁取代基效应的从头算研究

为寻找取代基效应与吡啶电子结构的关系，以吡啶Weng——水复合体为模型，应用从头算6-31G*基函数计算了43个包括邻、间、对位三组吡啶Weng化合物的电子结构。结果得到：⑴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；⑵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顾子相邻的H原子净电荷可描述诱导/场效应。⑶上述量化指数可用于描述取代吡啶Weng的酸性。

A QUANTUM CHEMICAL STUDY ON SUBSTITUTE EFFECTS OF PYRIDINIUM

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.