单参数法估算取代吡啶的电离常数和分配系数

Forecast pK_a and logP Values of the Substituted Pyridine by Natural Atomic Orbital Charges

用密度泛函理论（DFY）和B3LYP／3—21G基组，优化了24种已知取代吡啶类分子结构，发现吡啶环上氮原子的自然原子轨道电荷（NBO）值与其实验电离常数（10gK）值和正辛醇一水分配系数（10ge）之间均存在较好的线性关系（R。=0．98，恐=0．88）。计算了10种未知logKa／]ogP值的多取代吡啶化合物的NBO参数，代入拟合出的单参数线性方程，发现与流行软件ACDLab6．0预测得到的多取代吡啶的logKa／logP值接近，相关系数R在0．80～0．90之间，相对偏差在1％～3％之间。

Using the density functional theory （DFT） and B3LYP/3 -21G level group, optimization of the molecular structure of 24 - substituted pyridines, it was found on the pyridine ring nitrogen atom natural atomic orbitals charge value （NBO） and its experimental ionization constants values （ logKa ） and n - octanol - water partition coefficient （ logP）, there was a good linear relationship （R1 = 0. 98, R2 = 0. 88 ）. 10 kinds of unknown logKa/logP value of multi - substituted pyridine compounds NBO parameters were substituted into the fitted one -parameter linear equations. It was found that polysubstituted with popular software ACD Lab 6.0 was close to the forecast pyridine logKJlogP values, with the correlation coefficient R between 0. 80 ~ 0. 90 and the relative deviation between 1% -3 %.