The aldol condensation of acetone with acetophenone

Abstract

The kinetics and equilibria involved in the aldol condensation of acetone, acting as carbon acid, and acetophenone have been studied in aqueous alkaline solution. The enone isolated is the E isomer. The reactions are all first order in hydroxide, with rate and equilibrium constants (defined for E-enone as initial compound) of: k12 = (5.55 ± 0.17) × 10−6 M−1 s−1, k21 = (8.00 ± 0.40) × 10−6 M−1 s−1, K21 = (1.44 ± 0.55) (ketol to E-enone), K24 = 0.160 ± 0.033 (ketol to Z-enone), K32 = (1.89 ± 0.26) × 10−3 M−1 (acetone plus acetophenone to ketol), k23 = 0.180 ± 0.005 M−1 s−1, k32 = (3.41 ± 0.49) × 10−4 M−2 s−1. There is an equilibration of the two enones in base that is faster than hydration to the ketol: k14 = (3.14 ± 0.84) × 10−5 M−1 s−1; k41 = (2.81 ± 0.61) × 10−4 M−1 s−1; K14 = 0.112 ± 0.019. To analyze the behavior of the enone:ketol equililbrium system in acid we simultaneously fitted analytical data for all three species (E-enone, Z-enone, and ketol) to a kinetic model, so that the rate constants were determined by the best fit to all of the data for an experiment.