Synthesis and spectral characterization of methyl 9(10)-dialkylphosphonostearates

Dimethyl, diethyl, and di-n-butyl phosphites were reacted with methyl or ethyl oleates using thermally initiated radical reactions. Reactions were conducted with or without the presence of a dilauroyl peroxide initiator. The reactions gave mixture of isomers with the phosphorus attached at the 9 or 10 carbon of the stearates. High yields (94–97%) and high purity products (98–99% by GC) were obtained in the presence of the initiator, while without initiator, the reaction was very slow resulting in very low conversions (<50% after 6 days). The phosphonostearate products were positively identified and thoroughly characterized using GC with EI–MS, FTIR, and 1H-, 13C-, and 31P NMR spectra. GC achieved only partial resolution of the positional isomers. Principal component analysis was applied to successfully separate the MS–EI spectra of fractions from the 9- and 10-isomers. A mechanism to explain the observed MS fragmentation pattern and the relative abundances is proposed. 2D-NMR data analysis was applied to assign values of 13C- and 1H NMR shifts as well as PC and PH splitting constants. The molecular volume and the refractive indices of the phosphonostearates were determined experimentally and were found to be in agreement with the computationally predicted values using the PM3 semi-empirical method and the group-contribution method of Bondi.

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► Bio-based phosphonostearates were synthesized by radical reactions.
► Their MS–EI; FT-IR; 1H, 13C and 31P NMR were collected and reported.
► Mechanism of MS fragmentation was proposed and discussed.
► Literature NMR chemical shifts and splitting confirmed or corrected.
► Density and refractivity were evaluated and agree with the theoretical models.