Kinetic and thermodynamic analysis of hemp oil epoxidation with density functional theory insights into unsaturated fatty acid epoxidation and ring-opening reactions

Abstract

This study investigates the kinetic and thermodynamic aspects of hemp oil epoxidation, using an ion exchange resin catalyst for in-situ peracid generation. Reactions were explored across varying temperatures and concentrations of carboxylic acids and hydrogen peroxide. The reaction rate increased with temperature, as evidenced by the measured rate constants, which changed from 3.85 × 10⁻⁵ to 8.98 × 10⁻⁵ mol⁻¹s⁻¹ between 50 °C and 68 °C. This trend aligns with the experimentally determined activation energy (Ea = 38.1 ± 2.5 kJ mol⁻¹) and indicates a relatively low energy barrier for converting double bonds into oxirane rings. Furthermore, for the first time, density functional theory (DFT) was employed to analyze epoxidation of the primary unsaturated fatty acids in hemp oil-oleic, linoleic, and linolenic acids- which offered detailed thermodynamic (H, S) and kinetic (ΔG‡) parameters. Linolenic acid showed the highest reactivity, with Gibbs free energy changes as low as -790.8 kJ mol−1 and activation barriers of 118.6 kJ mol−1 in its reaction with performic acid. Epoxidation consistently surpassed oxirane cleavage via hydrolysis in both thermodynamic favorability and kinetics. These findings advance understanding of hemp oil epoxidation for bio-based material development, highlight the utility of DFT in assessing molecular reactivity, and provide a basis for optimizing renewable chemical synthesis.

Keywords

• Computational quantum chemistry
• Epoxidation
• Hemp oil
• Kinetic study
• Oxirane cleavage