在分子图的邻接矩阵基础上提出了一个新的连接性指数 mX ,该指数易于计算 ,对饱和烷烃有较高的结构区分能力 .mX与 85种链烷烃的标准生成焓、标准熵、标准生成自由能和沸点关联 ,相关系数多在 0 99以上 ,属于良好模型 ,能较好地反映化合物的结构特征 . A new connectivity index, mX, is proposed based on the adjacency matrix of the molecular graph, which is easy to calculate and has a high ability of structural differentiation for saturated alkanes. The standard enthalpies of formation, standard entropies and standard productions of mX and 85 kinds of paraffins The correlation between free energy and boiling point is more than 0 99, which is a good model and can well reflect the structural characteristics of the compounds.