The ring-opening reaction of cyclobutene radical cation and related rearrangements

Experiments described the cyclobutene radical cation (CB)+ ring opening and its conrotatory stereochemistry in the butadiene radical cation (BD)+ product. The CB ring opening was observed in two competing pathways which resulted to cis- and trans- BD+. The 298K activation enthalpies for the two processes differed only by less than i kcal/mol. Moreover, a transition state was found to exist in the bicyclobutane radical cation conversion to CB+.