To confirm the hierarchy of rates, renant > rred > rox(Ra,Sa), we determined each rate separately under conditions matching as closely as possible the operating conditions of the motor. The rate of enantiomerization, renant, (i.e., the rate of interconversion of (Ra)-4a and (Sa)-4a) was estimated from the barrier to rotation about the equivalent biaryl axis of the Mosher's ester derivative (S)-6a in a mixture of D2O and DMSO: renant((S)-6a) = 9.4 x 10 -1 • [4a] mM.s -1