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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+.

The adenine-thymine (AT) base pair geometry and transition state energy for double proton transfer resemble that of the imino-enol tautomer. The relaxation of geometry causes a decrease in the AT base pair energy and enhances A and Tz interaction enthalpy to levels 60% higher than that of canonical base. The small energy barrier and absence of zwitterionic A+T- and A-T+ structures are responsible for the AT component stability.

C4H6*+ potential energy surfaces (PES) were investigated using the UMP2 methodology in combination with UHF and B3LYP methods. The study expected to focus on the pathways for the C4H6*+ association and fragmentation processes. It was observed that the third C4H6*+ isomer possessing a methyl group, 1-butyne radical cation, needed a much higher activation. The most stable C4H5+ isomer was the methylcyclopropenium cation which may be formed readily from the methylcyclopropene radical cation.