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

Authors: Bantchev, Grigor; Biresaw, Girma; Vermillion, Karl; Appell, Michael

Submitted to: Spectrochimica Acta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/9/2013
Publication Date: 4/2/2013
Citation: Bantchev, G.B., Biresaw, G., Vermillion, K., Appell, M.D. 2013. Synthesis and spectral characterization of methyl 9(10)-dialkylphosphonostearates. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. 110:81-91.

Interpretive Summary: Novel bio-based products have been synthesized, purified, and characterized by spectroscopic methods. These materials are expected to be used as plasticizers, antimicrobial agents, flame retardants, and/or lubricant additives. Nevertheless, to be evaluated as high value components, these compounds need to be high purity and well characterized. Their spectral properties are needed for several purposes: first, to ensure their purity; second, to enable their identification and monitoring during production and use; and third, for validation and confirmation of theoretical methods for property predictions. Several spectroscopic methods were used for the evaluation of the new compounds, new data for the databases was generated, and some old data was corrected. Some properties of the compounds were compared with theoretical predictions, and the results were used confirm and expand them. The synthesized compounds will be further evaluated as potential bio-based value-added products. The spectroscopic data will allow for faster identification of the compounds, as well as their reaction and degradation during use. The future identification of compounds with some similarity of the structures will be facilitated.

Technical Abstract: 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 the lauroyl peroxide initiator. The reactions gave a mixture of isomers with the phosphorous 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 the 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, EI-MS, FTIR, and 1H-, 13C-, and 31P-NMR spectra. GC achieved only partial resolution of the positional isomers. A 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 abundance is proposed. 2D NMR data analysis was applied to assign values of 13C- and 1H-NMR shifts as well as P-C and P-H splitting constants. The molecular volume and the refractive indices of the phosphonostearates were determined experimentally and found to be in agreement with the computationally predicted values using the PM3 semi-empirical method and the group-contribution method of Bondi.