Acetylthiostearates – mass spectroscopy and NMR characterization

Authors: Bantchev, Grigor; Vermillion, Karl; Biresaw, Girma; Berhow, Mark

Submitted to: Journal of Sulfur Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/26/2019
Publication Date: 12/10/2019
Citation: Bantchev, G.B., Vermillion, K.E., Biresaw, G., Berhow, M.A. 2019. Acetylthiostearates – mass spectroscopy and NMR characterization. Journal of Sulfur Chemistry. 41(2):154-169. https://doi.org/10.1080/17415993.2019.1699928.
DOI: https://doi.org/10.1080/17415993.2019.1699928

Interpretive Summary: This research evaluated the spectral properties of several fatty acid sulfur-containing derivatives. Sulfur-containing derivatives often have valuable properties as lubricant additives, but there is a lack of cheap and effective biobased ones. Researchers from ARS, Peoria, IL, report a method to synthesize several sulfur-containing fatty acid derivatives and methods to spectroscopically identify their structures. The finding will be useful to scientists using characterized fatty acid derivatives, and scientists wanting to construct a structure-lubricating property relationship for sulfur-containing biobased materials.

Technical Abstract: 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 a 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 qusi-rac- forms of the isomers. Most often thioacetates are used as protecting groups or intermediary of thiol groups.