A New Approach to Synthesis of Benzyl Cinnamate: Kinetic and Thermodynamic Investigation

Abstract

Benzyl cinnamate is widely used in many fragrance compounds. The traditional methods to obtain benzyl cinnamate, including chemical synthesis or extracted from leaves, have many drawbacks. Recently, lipase-catalyzed synthesis of benzyl cinnamate provides us a promising alternative due to its high catalytic efficiency, mild reaction conditions, and green and environmentally friendly process. In this work, the purpose is to investigate the kinetics and thermodynamics of enzymatic synthesis of benzyl cinnamate. The objective of the current study was to investigate the kinetics and thermodynamics of enzymatic synthesis of benzyl cinnamate. The results showed that the reaction followed Ping-Pong mechanism having substrate inhibition. Furthermore, the kinetic and thermodynamic parameters were estimated. The inhibition constant KiB decreased with temperature enhancement, implying that the inhibition of benzyl alcohol on lipase could be depressed at high temperature. Moreover, the activation energy of the first-step reaction (52.46 kJ/mol) was much higher than that of the second-step reaction (12.97 kJ/mol), demonstrating that the first-step reaction was the rate-limiting reaction. The esterification process was found to be endothermic, with enthalpy value (ΔH) of +55.7 kJ/mol and entropy value (ΔS) of +170.2 J/mol K, respectively. Based on the change of Gibbs free energy (ΔG), enzymatic esterification of cinnamic acid would change from nonspontaneous to spontaneous reaction when raising temperature to above 53ºC. These gained information could be utilized to optimize the biosynthesis of benzyl cinnamate.