Theoretical studies on the mechanism of cycloaddition reaction of dichlorocarbene with C-60

The cycloaddition reaction of dichlorocarbene with C-60 has been studied by using the semi empirical method AM1. A reasonable mechanism of the reactio n has been suggested, All the geometries of the stationary points on the re action path way have been optimized by energy gradient technique and the tr ansition states were characterized by vibration frequency analysis. The cal culation results show that the reactions of dichlorocarbene with 6-6 or 6-5 bond of C-60 proceed via two steps: (1) Dichlorocarbene and C-60 form an i ntermediate complex with a pretty low barrier. (2) The intermediate complex forms the product C60CCl2. 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 dichorocar bene cycloaddition should take place across 6 - 6 bond rather than 6 - 5 bo nd of C-60 are explained from the reaction mechanism and kinetic factors.