C~6~0与二氯卡宾环加成反应机理的理论研究

用半经验AM1方法研究了C~6~0与单态二氯卡宾环加成反应的反应机理。采用Berny梯度法优化得到反应的过渡态，并进行了振动分析确认。计算结果表明：二氯卡宾在C~6~0的6-6或6-5键上的加成反应均分两步进行，第一步反应物经(类)过渡态Ⅰ生成中间配合物，第二步由中间配合物经过渡态Ⅱ变为产物。6-6加成反应的活化势垒较6-5加成反应的低121kJ·mol^-^1，从反应机理和动力学角度解释了6-6加成优于6-5加成的原因。

Theoretical studies on the mechanism of cycloaddition reaction of dichlorocarbene with C~6~0

The cycloaddition reaction of dichlorocarbene with C~6~0 has been studied by using the semi-empirical method AM1. A reasonable mechanism of the reaction has been suggested. All the geometries of the stationary points on the reaction path way have been optimized by energy gradient technique and the transition states were characterized by vibration frequency analysis. The calculation results show that the reactions of dichlorocarbene with 6-6 or 6-5 bond of C~6~0 proceed via two steps: (1) Dichlorocarbene and C~6~0 form an intermediate complex with a pretty low barrier. (2) The intermediate complex forms the product C~6~0 CCl~2. After being corrected by zero-point energies the barriers are 10.59kJ·mol^-^1 of 6-6 cycloaddition and 131.56kJ·mol^-^1 of 6-5 cycloaddition reactions respectively. The reasons that dichorocarbene cycloaddition should take place across 6-6 bond rather than 6-5 bond of C~6~0 are explained from the reaction mechanism and kinetic factors.