Acyl Migration Kinetics of 2-Monoacylglycerols from Soybean Oil via ¹H NMR
2007
Compton, David L. | Vermillion, Karl E. | Laszlo, Joseph A.
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.
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