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

Authors

  • Hongyan Chen,

    1. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, P.R. China
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  • Hongbing Ji

    Corresponding author
    1. School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, P.R. China
    2. School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, P.R. China
    • School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, P.R. China
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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. 1H-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, ΔγGmath image (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

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