CBS方法对单杂环体系C—H键解离焓的实验值评估

Assessment on Experimental Values of C H Bond Dissociation Enthalpies of Single Heterocyclic Molecular with CBS Methods

用高精度计算方法 CBS-4M,CBS-Q和CBS-QB3评估了26种单杂环分子的C-H键解离焓的实验值.结果表明,CBS-QB3方法最好,MD、MAD及RMSE分别为9.3、9.3和11.1 k J/mol.理论值与实验值的线性相关方程为y=0.928x+21.3,相关系数平方R2达0.980.通过自然键轨道分析后发现,杂原子的电负性使得五元杂环的自然电荷分布发生变化.

Three kinds of high precision computational methods,including CBS- 4M,CBS- Q and CBS- QB3,were used to evaluate C--H bond dissociation enthalpies （BDEs） of the 26 single heterocyclic molecular. The results show that CBS - QB3 method is the best one,of which the MD,MAD and RMSE are 9.3,9.3 and 1l. 1 kJ/mol respectively. Its theoretical and experimental values of linear correlation equation is y = 0. 928x ＋ 21. 3, and the correlation coefficient （R2） is 0. 980. In addition, there existes variation for the natural charge distribution of five-membered heterocycles after the natural bond orbital analysis（NBO）.