Abstract: Kinetic studies are reported for the Cope rearrangements of the 2-pheny1, 3- phenyl, 2-(a-naphthyl), 2-(P-naphthyl), 2, 4-diphenyl, and 2, 5-diphenyl derivatives of 1, 5- hexadiene. The results suggest that the transition state for the reaction is a biradicaloid akin to the 1, 4-cyclohexylene biradical.