取代羧酸pK_a的分子树拓扑研究

Molecular Tree Topological Research on pK_a Values of Substituted Carboxylic Acids

基于非氢原子i的酸性点价(δai)建构分子树拓扑指数(mT)及其分支指数(mTC)和叶指数(mTx),并提出表征诱导效应的叶指数(mT′x).通过最佳变量子集算法获得38种羧酸的pKa与0TC、1TC、0T′x的回归方程:pKa=3.0352-1.25700T′x-0.15540TC+0.07811TC,R=0.9766.通过Jackknife法检验,该模型具有总体稳健性.优于文献的七元最佳回归模型(R=0.957),与其分子力学方法(CoMFA)结果(R=0.988)较为接近.结果表明,所建拓扑指数是合理的,具有科学性基础.

Based on acidic point valence (δ~a_i) of non-hydrogen atom i, a novel molecular tree topological index (^(m)T) is constructed, together with its branch indices:trunk index (^(m)T_(C)) and leaf index( (^(m)T_(x))),and leaf index (^(m)T′_(x)) with characteristic inductive effect. A satisfactory linear equation between the ^(0)T_(C),^(1)T_(C),^(0)T′_(x) and pK_a of 38 substituted carboxylic acids is performed by using Leaps-Bounds follows:pK_a= 3.035 2-1.257 0 ^(0)T′_(x)-0.155 4()^(0)T_(C) +0.078 1()^(1)T_(C),R=0.976 6.Forthermore,a modified jackknifed test has been performed to validate the general stability of the model, showing that its correlativity is higher than that obtained by 7 variables relationship model (in which R=0.957), and close to that of CoMFA (in which R=0.988) found in the literature. The results from the present model prove that the indices are reasonable.