Grigor B. Bantchev

Free Radical Addition of Butanethiol to Vegetable Oil Double Bonds

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 were favored at low reaction temperatures and high butanethiol/vegetable oil ratios. Canola and corn oils 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-bond conversion and 61% isolated yields of the purified SMVO products were attained.

Elastohydrodynamic (EHD) Traction Properties of Seed Oils1

The elastohydrodynamic traction coefficient (tc) properties of nine seed oils of varying chemical structures, polyalphaolefin oil (PAO) and hexadecane, were investigated using a ball-on-disk traction apparatus. The seed oils were castor oil, a triglyceride with hydroxyl functional group; jojoba, a monoglyceride; and seven triglyceride seed oils with varying fatty acid compositions. Two types of experiments were conducted at constant temperature (40 or 100°C) and constant load (10, 20, 30, or 40 N): tc as a function of slide-to-roll ratio (srr) at 1 m/s entrainment speed (u); and tc as a function of u at 50% srr. In both types of experiments, tc increased with decreasing temperature, increasing load, and increasing srr. All u vs. tc experiments gave the familiar Stribeck-type profiles. A maximum in tc values was observed in some srr vs. tc experiments. Regression analysis showed excellent agreement between limiting tc (tc at 1 m/s u and 50% srr) values from these two types of experiments. Hexadecane and PAO displayed higher tc values than the seed oils, even though their viscosities were up to 80 and 7 times lower, respectively, than that of seed oils. This observation cannot be rationalized using molecular structure arguments. The results were attributed to differences in polarity between the two groups of oils. Unlike PAO and hexadecane, seed oils are polar, adsorb on friction surfaces, and lower boundary friction, which contributes to the lowering of tc in the EHD regime.

Synthesis and tribological investigation of lipoyl glycerides.

Lipoyl glycerides were synthesized by enzymatic transesterification of lipoic acid with high-oleic sunflower oil in 2-methyl-2-butanol solvent. The synthesis gave a crude product mixture comprising unreacted lipoic acid, free fatty acids, and several lipoyl glyceride structures of varying lipoic acid substitution. A more purified product mixture, devoid of unreacted lipoic acid and free fatty acids, was obtained in 61% yield. The crude and purified product mixtures were thoroughly characterized and their components positively identified. The tribological properties of the product mixtures were further investigated using a variety of methods. The product mixtures displayed significantly improved oxidation stability, cold-flow, and extreme pressure properties over those of the parent high-oleic sunflower oil. The extreme pressure results for the neat products showed a higher weld point for the crude than for the purified mixture. This was attributed to differences in the chemical properties of the components in the two product mixtures.

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 (1)H-, (13)C-, and (31)P 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 (13)C- and (1)H 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 were found to be in agreement with the computationally predicted values using the PM3 semi-empirical method and the group-contribution method of Bondi.

CHAPTER 4:Thiol-ene and H-Phosphonate-ene Reactions for Lipid Modification

This chapter is a short introduction to the thiol-ene reaction and includes the thiol-ene reaction as a click chemistry reaction, radical chain reactions, basic mechanisms and kinetics, the use of the thiol-ene reaction for the synthesis of novel bio-based materials (polymers, lubricants and coatings), addition of H-phosphonates to double bonds, some reaction information and bio-based products, and possible applications of the products (lubricants, plasticizers and anti-microbial agents).

Improvement of Lubricant Materials Using Ruthenium Isomerization

Production of an effective industrial lubricant additive from vegetable oils is a high profile and difficult undertaking. One candidate is alkyl 9(10)-dibutylphosphonostearate, which has been made through a radical transformation of alkyl 9-cis-octadecanoate. It is effective, but still suffers from drawbacks. In this report, that synthesis is combined with a ruthenium based isomerization process to create not just one, but an entire series of new chemical compounds. A low level of [Ru(CO)2(EtCO2)]n is first used for the isomerization of the starting material, then radical chemistry is employed. A series of methyl dibutylphosphonooctadecanoates was made. In an analogous fashion, trans-7-tetradecene was also isomerized and then polymerized. As in the phosphonate case, the follow-up chemistry could be performed in the presence of the residual isomerization catalyst. The alkane:alkene ratio, observed by 1H NMR, was found to change from 14:1 in the isomerized starting material to a value of 41:1 in the polymerized material. This methodology, isomerization in tandem with other reactions, gives suitable routes to both biobased polyolefins, and biobased phosphonates, potential key ingredients in biobased lubrication formulations.