Kinetics of the pinacol rearrangement of Propane-1,2-diol

Abstract

The pinacol rearrangement of propane-1,2-diol in aqueous acid gives propanal. The rate of loss of optical activity (k_α) is greater than the loss of diol (k_re) over the range of acid concentrations investigated. Also the ratio k_α/k_re decreases with the increasing acidity. A value of c. 0.5 has been obtained for the relative rates of oxygen exchange to racemization. Relative rates for the partitioning of a proposed carbocation intermediate have been calculated from these data.