DFT studies on the cascade rearrangement reactions of the cubylcarbinyl radical

DFT (U)B3LYP calculations with the 6‐311 + G** basis set were carried out to investigate the mechanisms of cascade rearrangement reactions (involving eight reaction channels) of the cubylcarbinyl radical (radical 1 ). The rate constant for each reaction step was calculated on the basis of the conventional transition state theory. The reaction channel from radical 1 to the 4‐(4‐methylenecyclobut‐2‐enyl) radical is preferred kinetically, while the reaction channel from radical 1 to the 1‐homocubyl radical is unfavorable. The mechanism of the conversion from radical 1 to the tricyclic dienes radical, which is experimentally uncertain, is predicted to be a stepwise process with the methylenesecocubyl radical as an intermediate instead of a concerted reaction. The energy barrier and rate constant of the initial reaction step are evaluated to be 2.8 kcal/mol and 3.0 × 10 10  s −1 , respectively, in excellent agreement with the corresponding experimental values. Copyright © 2010 John Wiley & Sons, Ltd.