Acyl Migration Kinetics of 2‐Monoacylglycerols from Soybean Oil via 1H NMR

Abstract

AbstractThe acyl migration kinetics of neat 2‐monoacylglycerol (2‐MAG) to form 1‐MAG was determined using 1H NMR spectroscopy to monitor the β‐proton integration ratios of the two species over time. 2‐MAG was synthesized by the Novozym 435‐catalyzed alcoholysis of soybean oil and isolated by solvent extraction or molecular distillation at a mole fraction (X2‐MAG) of 0.94 relative to total MAG. The kinetics parameters of the neat 2‐MAG acyl migration were investigated over the temperature range of 23–80 °C. The 2‐MAG mol fraction remained unchanged at 23 °C over the course of 168 h and reached an equilibrium of X2‐MAG = 0.09 at only 80 °C. Modeling of the kinetics data revealed a 2‐MAG half life (t1/2) of 3,500 and 22.8 h at 23 and 80 °C, respectively, with an activation energy of 79.0 ± 6.5 kJ mol−1. The use of 1H NMR spectroscopy proved an expedient method for monitoring the acyl migration in 2‐MAG compared to other reported methods (e.g. GC, HPLC, and 13C‐NMR spectroscopy), requiring no sample manipulation and minimizing the deleterious effects of high temperatures and solvent exposure.