Rate constants were determined for the forward and reverse rearrangements of the Cope- related pair, trans,-trans-lJ5-cyclodecadiene (3) and trans-1, 2-divinylcyclohexane (4). The rate of 4 43 was determined from the rate of racemization of (+)-4 (the two rate constants are identical), an indirect approach necessitated by the large equilibrium constant favoring 4; the ratio of forward and reverse rate constants yielded KWI~ Q= 2 X lo4 with AGXV= 9.4 kcal ...