Cyclization of Pseudoionone to β-lonone: Reaction Mechanism and Kinetics

Cyclization of pseudoionone (PI) to beta-ionone is an important reaction used in the synthesis of vitamin A and in perfumery. Though the reaction is used for commercial production, its mechanism and kinetics are not known, and the same holds for the optimal performance of the process. This paper deals with experimental investigations of reaction mechanism and kinetics. The inherent characteristics of the reaction such as heat of reaction, thermal stability, and reactants/products distribution in biphasic (sulfuric acid-toluene) system was investigated experimentally. To overcome the mass transfer limitations, the intrinsic kinetics was studied in a batch reactor using a solvent (1-nitropropane) miscible with the reactant and the homogeneous catalyst. It was revealed that the reaction consists of two steps with the first being rapid, while the second is relatively slower. Therefore, the kinetics of only the second step was investigated which was observed to be first order with an activation energy of 65 kJ/mol.