Efficient microwave‐assisted synthesis of glycerol monodecanoate

Solvent-free microwave-assisted synthesis was carried out to prepare 2,3-dihydroxypropyl decanoate, by esterification of decanoic acid in the presence of two distinct glycerol derivatives, glycidol and glycerol carbonate, respectively. The process described is based on microwaves heating source with electrical power in the range of 200 W to 400 W, involving stoichiometric proportions of decanoic acid and glycerol derivatives, and using catalytic amounts of TBAI used as organocatalyst. Conversion and selectivity rates of esterification reactions were monitored by 1H and 13C{1H} NMR spectroscopy. The predominantly formed ester, 2,3-dihydroxypropyl decanoate was fully characterized by infrared and NMR spectroscopy, mass spectrometry and elemental analysis. Compared with the classical heating procedures, and whatever the glycerol derivatives used, total conversions were obtained with considerably reduced reaction times. Thus, under 300 W, esterification requires only one minute exposure from glycidol and five minutes from glycerol carbonate. The use of heating with conventional oil bath conditions needs residence times of more than one hour (even 24 hours in the case of glycerol carbonate). The microwave-assisted synthesis also notably enhances the selectivity in 2,3-dihydroxypropyl decanoate (at 300 W, 90 and 50 %, respectively), reinforcing the efficiency and the interest of the method. Practical applications: The results establish that microwave heating is well suited for the solvent-free synthesis of glycerol monodecanoate from decanoic acid and two glycerol derivatives, glycidol and glycerol carbonate. Reaction times are drastically reduced, and in both cases, marked improvements of the conversion and selectivity are recorded. The target α-monoglyceride, 2,3-dihydroxypropyl decanoate, has various potential applications such as antimicrobial properties, bacterial inhibitory activity, or denture disinfectant.