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

TLDR: In this article, the acyl migration kinetics of neat 2-monoacylglycerol (2-MAG) to form 1-MAG were determined using 1H NMR spectroscopy to monitor the β-proton integration ratios of the two species over time.

Abstract: The 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 (X 2-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 X 2-MAG = 0.09 at only 80 °C. Modeling of the kinetics data revealed a 2-MAG half life (t 1/2) 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.