影响烷烃辛烷值高低的结构因素

STRUCTURAL FACTORS AFFECTING OCTANE NUMBER OF PARAFFIN

利用量子化学方法计算了40种不同结构C5～C10烷烃分子的电荷分布、前线轨道能量、偶极矩、表面积、体积等反映烃类分子微观特征的电子结构参数和几何结构参数,同时计算了这些烷烃不同类型的拓扑指数。采用遗传函数算法(GFA)对这些烷烃的马达法辛烷值与结构参数之间的关系进行了回归分析,建立了物理意义明确的烷烃辛烷值与其结构参数之间的定量关系方程。该方程揭示了烷烃分子前线轨道间隙和分子表面积是影响其辛烷值高低的主要结构因素。分子前线轨道间隙越低,分子表面积越小,烷烃的辛烷值越高。依据这2个结构参数,利用构建的关系方程,可以对烷烃的辛烷值进行较为准确地预测。方程相关系数平方为0.882,交叉检验相关系数平方为0.848,表明方程具有较强的预测能力。

Various structural and electronic descriptors of 40 paraffin of C5～C10,such as charge distribution,HOMO and LUMO Eigenvalues,dipole,molecular surface area,molecular volume,etc.,were calculated by using quantum method,and different kinds of topological descriptors were calculated as well.GFA method was selected to elucidate the relationship between the structure of paraffin and their motor octane numbers.As a result,a quantitative equation with clear physical meanings was set up,which showed that LUMO-HOMO gap and molecular surface area of paraffin were the two main structural factors for their octane number.The narrower the LUMO-HOMO gap,the higher the octane number,and the smaller the molecular surface area,the higher the octane number.With these two structural descriptors,the established equation could be used to properly predict motor octane number of paraffin with the square of correlation coefficient of 0.882 and the square of cross-validated coefficient of 0.848,which means that the equation has a quite strong predictability for the octane number of paraffin.