Ten meta- and para-substituted benzoic acids with substituents N+(CH3)3, CH2N+(CH3)3, CH2Py+, CH2SO2CH3 and PO(OCH3)2 were synthesized. Dissociation constants of these acids were determined in five solvents (water, ethanol, methanol, N,N-dimethylformamide, dimethyl sulfoxide) at 25 °C. Dissociation constants of benzoic acid derivatives with other substituents H, CH3, NHCOCH3, OCH3, F, Cl, Br, I, COCH3, CN, NO2, SO2CH3 were taken from the literature (calibration set). Substituent constants σm, σp, σI, σR, and σi for substituents N+(CH3)3, CH2N+(CH3)3, CH2Py+, CH2SO2CH3, and PO(OCH3)2 were calculated by nonlinear and PLS (partial least-square method with latent variables) calibration in three correlation models using the calibration set. Nonlinear regression appears more suitable and more universal than PLS calibration. The advantage of nonlinear regression is its independence on possibly missing data in the given solvent, evaluation of precision (standard deviation), the accessibility of necessary software, and easy calculation. However, in contrast to PLS calibration, this procedure fails in calculation of substituent constants with description of properties of substituents (substituent constants σI, σR). The obtained values of substituent constants are in good agreement with those published in the literature.
合成了十种带有取代基N+ (CH3) 3、CH2N+ (CH3) 3、CH2Py+、CH2SO2CH3和PO (OCH3) 2的苯甲酸类衍生物。在25°C下,测定了这些酸在五种溶剂(水、乙醇、甲醇、N,N-二甲基甲酰胺、二甲基亚砜)中的解离常数。从文献中选取了其他取代基为H、CH3、NHCOCH3、OCH3、F、Cl、Br、I、COCH3、CN、NO2、SO2CH3的苯甲酸衍生物的解离常数(校准集)。通过非线性和PLS(偏最小二乘法)校准,在三个相关模型中计算了取代基N+ (CH3) 3、CH2N+ (CH3) 3、CH2Py+、CH2SO2CH3和PO (OCH3) 2的取代基常数σm、σp、σI、σR和σi。非线性回归比PLS校准更适用和更普遍。非线性回归的优点是不依赖于给定溶剂中可能缺失的数据,可以评估精度(标准偏差),易于计算所需的软件和易于计算。然而,与PLS校准相比,这种方法在描述取代基特性(取代基常数σI、σR)时失败。得到的取代基常数值与文献中发表的值相符。