Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2008
Publication Date: January 23, 2009
Citation: Bantchev, G.B., Kenar, J.A., Biresaw, G., Han, M.G. 2009. Free Radical Addition of Butanethiol to Vegetable Oil Double Bonds. Journal of Agricultural and Food Chemistry. 57(4):1281-1290. Available: http://pubs.acs.org/doi/abs/10.1021/jf802774g. Interpretive Summary: Widespread use of vegetable oils in lubrication is hindered by their poor thermal and oxidative stability, which arises mainly from the presence of unsaturations in the vegetable oil molecules. Vegetable oils also suffer from poor low temperature properties, and also lack extreme pressure (EP) properties. EP properties are essential for application of vegetable oils in various lubrication processes including metalworking. In the work described here, the unsaturations in the vegetable oils were converted into sulfides through a photochemical reaction. The resulting sulfide modified vegetable oil (SMVO) is expected to have excellent EP and thermal/oxidative stability. In addition, because of the introduction of branching in the vegetable oil molecule, it is expected that the SMVO will have improved low-temperature properties. These improvements in the properties of vegetable oils can lead to a widespread application of SMVOs in lubrication, thereby creating new demand for surplus seed oils.
Technical Abstract: Butanethiol was used in ultraviolet-initiated thiol-ene reaction with canola and corn oils to produce sulfide modified vegetable oils (SMVO). The crude SMVO product was successfully purified by solvent extraction, vacuum evaporation and silica gel chromatography. The SMVO products were characterized by nuclear magnetic resonance and Fourier transform infrared spectroscopy. Further product characterization and analysis was conducted using GC and GC-MS on the fatty acid methyl esters obtained by the transesterification of the SMVO products. Investigation of the effect of reaction conditions showed that high yield and high conversion of double bonds into thiol was favored at low reaction temperatures and high butanethiol:vegetable oil ratio. Canola and corn oil gave similar double bond conversions and yields of the desired SMVO product even though they have big differences in the relative numbers of single and multiple double bonds in their structures. Under best reaction conditions, up to 97% of double bonds conversion and 61% isolated yields of the purified SMVO products were attained.