Ab Initio calculations on the isomerization of the dimethylene cyclobutene and 1,2,4,5-hexatetraene radical cations to the benzene structure

Ab initio calculations at the MRCI//ROHF/6-31G** level suggest that stable C₆H₆ radical cations formed from dimethylene cyclobutene and 1,2,4,5-hexatetraene either retain the structure of the parent neutral molecule or isomerize to the benzene structure. The previous suggestion from photodissociation experiments that part of the ions from dimethylene cyclobutene isomerize to the 1,2,4,5-hexatetraene structure is not supported by the present results.