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应用密度泛函B3LYP/6-311++G~(?)法得30种羧酸分子的优势构象,再计算羧酸-水构成的氢键复合物,获得优势构象和复合物的结构参数,并将这些参数与羧酸pKa值相比。羧基C-O键长、羧基氢自然键轨道电荷以及复合物的氢键键长和结合能等参数,与羧酸pKa实验值具有良好的线性关系。以水为探针分子获得氢键复合物结构参数的方法,可预期在预测其它含有酸性基团化合物酸性的强弱方面推广应用。
The dominant conformations of 30 kinds of carboxylic acid molecules were obtained by density functional theory B3LYP / 6-311 ++ G ~ (?) Method. Then, the hydrogen bond complex composed of carboxylic acid and water was calculated to obtain the dominant conformation and the structural parameters of the complex, These parameters are compared to the pKa value of the carboxylic acid. Carboxyl C-O bond length, carboxyl hydrogen bond orbital charge as well as the hydrogen bond length and binding energy of the complex and other parameters, and the carboxylic acid pKa experimental values have a good linear relationship. The method of using water as a probe molecule to obtain structural parameters of hydrogen bonding complexes can be expected to be widely used in predicting the acidity of other acidic group-containing compounds.