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ARS Home » Midwest Area » Peoria, Illinois » National Center for Agricultural Utilization Research » Bio-oils Research » Research » Publications at this Location » Publication #298780

Title: Radical-initiated reaction of methyl linoleate with dialkyl phosphites

item Bantchev, Grigor
item Biresaw, Girma
item Palmquist, Debra
item Murray, Rex

Submitted to: Journal of the American Oil Chemists' Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/11/2016
Publication Date: 6/1/2016
Citation: Bantchev, G.B., Biresaw, G., Palmquist, D.E., Murray, R.E. 2016. Radical-initiated reaction of methyl linoleate with dialkyl phosphites. Journal of the American Oil Chemists' Society. 93(6):859-868.

Interpretive Summary: The synthesis and characterization of phosphono-derivatives of linoleic acid (PDLA) are reported. Phosphono-derivatives of oleic acid (PDOA) have been reported to have antibacterial, plasticizing, and anti-wear properties, but PDLA have not been synthesized previously. Both oleic and linoleic acids are fatty acids, but linoleic acid is of higher abundance in many commodity vegetable oils, such as soybean and corn. Linoleic acid has more reactive sites than oleic acid, which makes the range of possible products and their properties wider, requiring more knowledge about the synthetic procedures, and possibly rewarding at the end with a broader range of useful properties. In the current study, an optimization of the conditions for the synthesis of the PDLA is reported. Spectra, which can help recognition of PDLA and similar products, are also reported.

Technical Abstract: The addition of dialkyl phosphite (methyl, ethyl and n-butyl) to methyl linoleate (MeLin) double bonds was investigated. The reaction proved to be more challenging than the analogous reaction with methyl oleate (MeOl), due to inhibition of the radical reaction by the bis-allylic hydrogens of MeLin and the lower reactivity of MeLin double bonds. However, we demonstrated that this self-inhibition problem can be solved by simply keeping the MeLin reagent at low concentrations, while keeping the dialkyl phosphite at high concentrations. For optimization of the reaction,four different radical initiators were investigated: dilauroyl peroxide (LP), 2,2'-azobis(2-methylpropionitrile) (AIBN), tert-butyl perbenzoate (t-BP), and tert-butyl peroxide (TOOT). The initiators were used at temperatures that provided a half-life of 10 h: 64, 64, 104, and 125 °C respectively for LP, AIBN, t-BP, and TOOT. The tests showed the reaction to be faster at higher temperatures, but transesterification of the ester groups was also observed at elevated temperatures. t-BP was chosen as an optimal initiator for carrying the reaction. The apparent order of reactivity of the dimethyl, diethyl and di-n-butyl phosphites (Me >Et /n-Bu) towards MeLin was due to differences in their molar volumes. When the concentrations of dialkyl phosphite were kept the same, the order reversed (n-BU > Et~Me). GC-MS spectra of the resulting phophonates are reported and the main fragments assigned.