Alkaline hydrolysis of cinnamaldehyde to benzaldehyde in the presence of β‐cyclodextrin

Abstract A facile, novel, and cost‐effective alkaline hydrolysis process of cinnamaldehyde to benzaldehyde under rather mild conditions has been investigated systematically in the presence of β‐cyclodextrin (β‐CD), with water as the only solvent. β‐CD could form inclusion complex with cinnamaldehyde in water, with molar ratio of 1:1, so as to promote the reaction selectivity. The complex has been investigated experimentally and with computational methods. 1 H‐NMR, ROESY, UV–Vis, and FTIR have been utilized to analyze the inclusion complex. It shows that the equilibrium constant for inclusion (Ka) is 363 M −1 , and the standard Gibbs function for the reaction, Δγ G (298 K), is −14.6 kJ mol −1 . In addition, the structures of the proposed inclusion compounds were optimized with hybrid ONIOM theory. Benzaldehyde could be obtained at an yield of 42% under optimum conditions [50°C, 18 h, 2% NaOH (w/v), cinnamaldehyde:β‐CD (molar ratio) = 1:1]. To explain the experimental data, NMR, FTIR, and elemental analysis results were used to determine the main reaction by‐product 1‐naphthalenemethanol. A feasible reaction mechanism including the retro‐Aldol condensation of cinnamaldehyde and the Aldol condensation of acetaldehyde and cinnamaldehyde in basic aqueous β‐CD solution has been proposed. The calculated activation energy for the reaction was 45.27 kJ mol −1 by initial concentrations method. © 2009 American Institute of Chemical Engineers AIChE J, 2010