取代苯甲酸羧基上H和O原子的部分电荷与Hammett常数之间的线性关系

Linear Relationship Between the Partial Charges of H and O Atoms in Carboxyl of Substituted Benzoic Acid and the Hammett Constants

采用密度泛函分析了取代苯甲酸中羧基上的H1原子和2个氧原子O2和O3的电荷与取代基的Hammett常数之间的线性关系.比较了不同密度泛函和电荷计算方法B3LYP/6-311G*/(NBO,Mulliken),(BLYP,BP,PWC)/DNP/(Hirshfeld,Mulliken)对上述线性相关系数的影响.结果表明,BLYP/DNP/Hirsh-feld方法的计算精度高且计算速度快.使用BLYP/DNP/Hirshfeld方法计算了70个取代苯甲酸的部分电荷,发现H1,O2和O3原子的电荷与取代基Hammett常数σp和σm之间的线性相关系数可达到0.98以上,其中O2的电荷和Hammett常数的线性相关性最好.O2的电荷值可以作为Hammett常数的替代,用于结构性能定量分析,也可以用于预测取代基的Hammett常数.

The linear dependence between the partial charges of HI, O2 and O3 atoms in carboxyl of substituted benzoic acid and Hammett constants was analyzed by density functional theory（DFT）. Different density functional and partial charge computation methods [ B3LYP/6-311G＊/（ NBO, Mulliken）, （ BLYP, BP, PWC）/DNP/（ Hirshfeld, Mulliken） ] were used to evaluate the above linear relationship. It was found that BLYP/DNP/HirshfeId had high accuracy and high computational speed. Seventy substituted benzoic acid com- pounds were computed. The results show that the linear correlation coefficient between the partial charges of HI, O2 and O3 atoms and σp and σm is higher than 0.98. The best linear relationship occurred between the partial charge of O2 atom and Hammen constant. The partial charge of O2 atom could be used as substitute of Hammett constant in the quantitative structure property analysis and to predict Hammett constant.