直接键连原子间的NMR偶合常数的自然杂化轨道研究

THE STUDY OF THE MUCLEAR SPIN－SPIN COUPLING CONSTANTS BETWEEN DIRECTLY BONDED ATOMS BY NATURAL HYBRID ORBITALS Ⅳ ^(13)C－^(15)N and^(13)C－^(19)F Nuclear Spin－Spin Coupling Constants^1J_(CN) and ~1J_(CF)

首次报道了直接计算偶合常数￣１Ｊ＿（ＣＮ）和￣１Ｊ＿（ＣＦ）的线性关系式，结果表明，￣１Ｊ（ＣＮ）和￣１Ｊ＿（ＣＦ）主要由成键原子的轨道杂化作用和键极性这两种结构因素所决定，且偶合相互作用中的Ｆｅｒｍｉ接触项仍是最主要的．为从简单价键理论角度解释并计算Ｊ＿（ＣＮ）和Ｊ＿（ＣＦ）的值提供了简便直观的方法．

The good relationships are presented which permit efficient calculation of the ^(13)C－^(15)N^(13)C －N and (13)C－^(19)F nuclear spin－spin coupling constants. The method is applied withwith the CNDO／2olecular orbital approximation and natural hybrid orbitai schemeto a number of substituted hydrocarbons．Generally good agreement with theexperimental data supports the idea that the hybridization and bond polarity，and theFermi contact term are do minant factors in determining carbon－nitrogen and carbon－fluorine spin－spin coupling constants across one bond．This pennitsus to interpret and calculate the ~1J_(CN) and ~1J_(CF) values based on he simple valenee bondtheory.