Synthesis and characterization of phosphonates from methyl linoleate and vegetable oils

Authors: Bantchev, Grigor; Moser, Bryan; Murray, Rex; Biresaw, Girma; Hughes, Stephen

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2016
Publication Date: 11/28/2016
Publication URL: https://handle.nal.usda.gov/10113/63331
Citation: Bantchev, G.B., Moser, B.R., Murray, R.E., Biresaw, G., Hughes, S.R. 2016. Synthesis and characterization of phosphonates from methyl linoleate and vegetable oils. Journal of the American Oil Chemists' Society. 93(12):1671-1682.

Interpretive Summary: Novel biobased phosphorus-containing lipid derivatives were synthesized and characterized. While phosphonates (a type of chemical with phosphorus-carbon bond) obtained from alkyl oleates (a kind of fatty acid) are known to have good property as lubricant additives, only a limited number of them have been synthesized to date. All previously known fatty phosphonates were derivatives of oleic acid. This means that for their production, the vegetable oils need to be separated into their components and then only part of the components could be used for the phosphonate synthesis. With the current publication, researchers from the USDA-ARS-NCAUR located in Peoria, Illinois, report for the first time successful syntheses and characterization of phosphonates directly from vegetable oils. The syntheses were done on a large enough scale for the products to be evaluated in lubrication tests. Further scaling-up of the production is possible. The characterizations are valuable for future identification of similar products.

Technical Abstract: Phosphonates were synthesized on a medium scale (~200 g) from three lipids–methyl linoleate (MeLin), high-oleic sunflower oil (HOSO) and soybean oil (SBO), and three dialkyl phosphites–methyl, ethyl and n-butyl, using a radical initiator. A staged addition of the lipid and the initiator was used to achieve good yields. Good results were observed with MeLin (94-99% conversions of the double bonds, as determined by NMR, and 83-99% isolated yields) and HOSO (99-100% NMR conversions, 87-96% isolated yields) using tert-butyl perbenzoate as the initiator. With SBO, benzoyl peroxide was used as the initiator, due to its capability to generate radicals at a higher rate at slightly lower temperatures, and thus to shorten the reaction time. Conversions of 91-93% (by NMR) and isolated yields of 80-94% were achieved. The progress of the reaction was monitored with GC-MS. The products were characterized using 1H, 13C and 31P NMR, IR and gel permeation chromatography. A prolonged reaction led to some transesterification between the carboxylic and phosphite ester groups. Conditions favoring higher reaction rates led to the formation of more oligomers and benzoate fatty ester byproducts. The benzoate fatty ester byproducts were formed by the attack of a benzoate radical on a double bond. The more double bonds that were present per lipid molecule, the more oligomers were formed: MeLin 2-8%, HOSO 3-9% and SBO 8-29%.