Abstract: The photochemistry of 5, 5-diphenyl-l, 3-~ yclohexadiene was investigated for comparison with that of l-methylene-4, 4-diphenyl-2-cyclohexene in order to determine the effect of a molecular free rotor on the reaction multiplicity. In contrast to the 4, 4-diphenyl diene, whose triplet proved totally unreactive, the. 5, 5-diene triplet rearranged smoothly via a di-a-methane mechanism. This difference is attributed to a free rotor effect in which the ...
