中文摘要：

运用分子轨道理论中的半经验MINDO／3，MNDO与PM3量子化学计算方法分别对松香中的枞酸分子进行几何结构优化，结果表明，3种方法预测枞酸菲环骨架内的键长、键角、两面角结果与文献值基本一致，而菲环外羧基及异丙基的键长、键角和两面角计算值与文献值有较大偏差，这是由于枞酸分子之间氢键作用以及异丙基热运动比较强烈影响的缘故。在不考虑羧基及异丙基相关的键长、键角和两面角之后，发现PM3方法计算的键长、键角与两面角的结果与文献值比较吻合，计算值与文献值的相关系数R^2分别为0．96432、0．91989和0．99912，而MINDO／3和MNDO的计算值与文献值偏差稍为大些。

英文摘要：

The optimization of geometrical structure of abietic acid was carried out by three semi - emperical molecular orbital methods of MINDO/3, MNDO, PM3. Thb results showed that, the calculated values of bond length, bond angle, dihedral angle inside phenanthrene ring of abietic acid by three methods were in agreement with the val- ues in literature, but there was large deviation between the calculated values of corresponding bond parameters of carboxyl groups together with isopropyl groups outside the phenanthrene ring and the values in the literature, because of hydrogen bond interaction in abietic acid molecules and strong thermal motion of the isopropyl groups. It was find that the calculated data of bond lengths, bond angles and dihedral angle by the PM3 methods were in good agreement with the literature data after neglecting the related bond parameter of the carboxyl and the isopropyl groups, and the square of correlate coefficient of the bond length, bond angle, dihedral angle were 0. 964 32, 0. 883 92, and 0.999 12, respectively, while the deviations by the methods of MINDO/3 and MNDO were larger.