Acetylthiostearates - mass spectroscopy and NMR characterization*

Oleic and linoleic acids are common fatty acids in commodity vegetable oils. Their modification into sulfur-containing molecules can be a route for producing biobased lubricants. We investigated modification of methyl oleate and methyl linoleate with thioacetic acid using UV-initiated thio-ene reaction to obtain methyl (acetylthio)stearates and methyl bis(acetylthio)stearates, respectively. Small amounts of acetyldithio derivatives were also detected. The products were characterized by Electron Impact Mass Spectrometry, High Resolution Mass Spectrometry, and 1- and 2-D NMR. The MS confirmed the anticipated molecular formulas. The fragmentation patterns can be explained with predominant breakage of carbon-sulfur bonds. The isomers of methyl bis(acetylthio)stearates were partially separated by chromatography, and some characteristic NMR peaks were identified and compared with the ones predicted by software. NMR showed distinct patterns of the quasi-meso- and quasi-rac- forms of the isomers. Most often thioacetates are used as protecting groups or intermediary of thiol groups.