Chemical and physical properties of isomeric glyceryl monoethers

Abstract

Long-chain saturated and mono- and diunsaturated 1- and 2-glyceryl monoethers were synthesized by reacting 1,2-isopropylidene and 1.3-benzylidene glycerol potassium salts with alkyl halides in the preparation of the saturated monoethers, and with alkenyl-p-toluenesulfonates in the preparation of the unsaturated monoethers, followed by hydrolysis of the blocking groups with boric acid. The progress of the reaction was monitored by gasliquid chromatography (GLC) of the reaction mixture. The 2-glyceryl ethers, with two exceptions, had not been prepared previously. Normal propyl and 3-pentyl octadecyl ethers also were synthesized to aid in the interpretation of infrared (IR) and nuclear magnetic resonance (NMR) spectra. All the ethers prepared were purified by preparative thin-layer chromatography (TLC) and crystallization. Their purity was found to be greater than 95%, as determined by TLC and GLC, supported by NMR and IR spectra. The isomeric 1- and 2-glyceryl ethers were separated on Silica Gel G adsorbent layers impregnated with either sodium arsenite or boric acid and their TLC behavior interpreted, based on the polarity of the complexes formed. Melting point determinations indicated more than one polymorphic form. Comparison of IR and NMR spectra of the saturated and unsaturated isomeric glyceryl ethers, and various derivatives, demonstrated the applicability of these spectroscopy methods for characterization and structural determination, in addition to distinguishing between the two isomeric forms.