Cis-Unsaturated fatty acid products by hydrogenation with chromium hexacarbonyl

The use of Cr(CO)₆ was investigated to convert polyunsaturated fats intocis unsaturated products. With methyl sorbate, the same order of selectivity for the formation ofcis-3-hexenoate was demonstrated for Cr(CO)₆ as for the arene-Cr(CO)₃ complexes. With conjugated fatty esters, the stereoselectivity of Cr(CO)₆ toward thetrans, trans diene system was particularly high in acetone. However, this solvent was not suitable at elevated temperatures required to hydrogenatecis, trans- andcis, cis-conjugated dienes (175 C) and nonconjugated soybean oil (200 C). Reaction parameters were analyzed statistically to optimize hydrogenation of methyl sorbate and soybean oil. To achieve acceptable oxidative stability, it is necessary to reduce the linolenate constituent of soybean oil below 1–3%. When this is done commercially with conventional heterogenous catalysts, the hydrogenated products contain more than 15%trans unsaturation. By hydrogenating soybean oil with Cr(CO)₆ (200 C, 500 psi H₂, 1% catalyst in hexane solution), the product contains less than 3% each of linolenate andtrans unsaturation. Recycling of Cr(CO)₆ catalyst by sublimation was carried through three hydrogenations of soybean oil, but, about 10% of the chromium was lost in each cycle by decomposition. The hydrogenation mechanism of Cr(CO)₆ is compared with that of arene-Cr(CO)₃ complexes. Presented in part at Seventh Conference on Catalysis in Organic Syntheses, Chicago, Illinois, June 5–7, 1978.     

Acetal derivatives of methyl 9(10)-formylstearate: Plasticizers for PVC

Several acetals and an enol ether were prepared from methyl 9(10)-formylstearate and characterized with respect to their thermal, spectroscopic and chromatographic properties. These low-melting (below −80 C) compounds were generally compatible as secondary poly(vinyl chloride) plasticizers and imparted low-temperature properties that were intermediate between those obtained with dioctyl phthalate and dioctyl sebacate. Presented at AOCS Meeting, Atlantic City, October 1971. N. Market. Nutr. Res. Div., ARS, USDA.     

Poly(amide-acetals) and poly(ester-acetals) from polyol acetals of methyl 9(10)-formylstearate: Preparation and physical characterization

Condensation polymers were prepared from the pentaerythritol acetal of methyl 9(10)-formylstearate by reaction with diamines and with ethylene glycol. The glycerol acetal was self-condensed to a poly(ester-acetal) and also copolymerized with caprolactam. A novel step growth, addition polymerization was carried out with ethylene bis[9(10)-methoxymethylenesterate] and pentaerythritol. Physical and spectral (infrared and nuclear magnetic resonance) properties of the various products were determined. In general, the long C₈–C₉ side chains in the polymers of the pentaerythritol acetal of methyl 9(10)-formylstearate reduced crystallinity to such a degree that, unlike polymers from methyl azelaaldehydate pentaerythritol acetal, they were soluble in the more ordinary solvents, e.g., chloroform and tetrahydrofuran. Presented in part at the 45th Fall AOCS Meeting, Atlantic City, New Jersey, October 3–6, 1971.     

Chromatographic separation and identification of nylon-9 intermediates and coproducts derived from soybean oil

9-Aminononanoic acid, 9-aminononanamide, and related compounds derived from soybean oil by reactions, including reductive ozonolysis and reductive amination, were separated on an analytical scale either by gas liquid chromatography of trifluoroacetylated or trimethylsilylated derivatives or by thin layer chromatography and on a preparative scale by ion-exchange chromatography. Comparative analyses also were carried out with certain homologous ω-amino acids and amines. Presented at the AOCS Meeting, Chicago, September 1973. ARS, USDA.     

Hydroformylation with recycled rhodium catalyst and one-step esterification-acetalation: A process for methyl 9(10)-methoxymethylenestearate from oleic acid

Previous studies on hydroformylation of methyl oleate with rhodium and triphenylphosphine or triphenylphosphite have led to a laboratory process for recycling the precious metal catalyst. Another catalyst recycling process has now been studied as the basis for converting commercially available oleic acid into the enol ether of methyl formylstearate. The process involves one-step esterification-acetalation of formylstearic acid made by hydroformylating oleic acid with rhodium and triphenylphosphine. Esterification-acetalation is done in a recycling system with methanol, an acid-exchange resin for catalysis, and molecular sieves to remove water from the reaction mixture. The dimethyl acetal methyl ester formed from formylstearic acid is thermally cracked and distilled in one pot to produce the enol ether, methyl methoxymethylenestearate. The soluble rhodium catalyst in the distillation residue is combined with the insoluble catalyst from filtration and recycled for hydroformylation. The product methoxymethylenestearate is a versatile and stable derivative for various potential industrial applications. Presented at the AOCS meeting, Cincinnati, September 1975.     

cis-bond-producing hydrogenation of polyunsaturates catalyzed by polymer-complexed Cr(CO)3 catalysts

cis-Bond-producing chromium carbonyl catalysts were prepared by complexing conventional or macroreticular, styrene-divinylbenzene copolymers or cross-linked poly (vinyl benzoate) with Cr(CO)₆. With one exception, these polymer-Cr(CO)₃ catalysts were as selective as the corresponding homogeneous arene-Cr(CO)₃ complexes for the formation ofcis-monoenes from methyl sorbate and from conjugated, polyunsaturated fatty esters in cyclohexane. Although several of the polymer catalysts were very active when fresh, they all lost activity on recycling. They could not be recycled more than two times before a marked decrease in activity occurred due to loss of Cr, as shown by elemental analysis and infrared absorption in the recovered catalyst. Thermal analysis indicated instability of the polymer complexes at hydrogenation temperatures.     

Cr(CO)3-complexed,silica-bonded polyphenylsiloxane as a stereoselective catalyst for hydrogenation of sorbate and soybean methyl esters

A silica-bonded complex was prepared by reacting polyphenylsiloxane with silylated Chromosorb and then with Cr(CO)₆. This complex catalyzed stereoselective hydrogenation of sorbate tocis-3-hexenoate. Soybean methyl esters were hydrogenated at 210 C in cyclohexane to form products high incis unsaturation. The recovered catalyst could be recycled once with methyl sorbate. IR showed decreased Cr(CO)₃ in the recovered catalysts, and the hydrogenation products contained inactive Cr.     

Synthesis and characterization of triacylglycerols containing linoleate and linolenate

Triacylglycerols containing linoleate and linolenate found in vegetable oils were synthesized in gram quantities for oxidation studies. Two acylation methods were examined to convert diacylglycerols or monoacylglycerols to the desired triacylglycerols. Acylations with fatty acid and 1,1′-dicyclohexylcarbodiimide in the presence of 4-dimethylaminopyridine were more rapid, gave triacylglycerols of better isomeric purities and generally better overall yields than the acylations with acid chloride in pyridine. The functional and isomeric purity of the synthetic triacylglycerols were investigated by thin-layer and gas-liquid chromatography of the methyl esters, by lipase hydrolysis, and by¹³C NMR. Quantitative¹³C NMR provided a valuable tool to determine isomeric structures of the unsaturated triacylglycerols and complemented the lipase hydrolysis method. The triacylglycerols purified by dry column chromatography were obtained in the following respective percent yields, functional and isomeric purities: LLLn, 92.1, 99.4, 98.1; LLnLn, 91.7, 99.2, 97.4; LLnL, 84.2, 99.7, 98.9; and LnLLn 77.5, 97.8, 99.0 (where L=linoleoyl and Ln=linolenoyl glycerol residues). These synthetic triacylglycerols are valuable models to elucidate the interrelationship of unsaturated fatty acids on the oxidative stability of polyunraturated vegetable oils. Presented in part at the AOCS meeting in Phoenix, AZ in May 1988.     

Ethylene and dimethyl acetals from hydroformylated linseed,soybean, and safflower methyl esters as plasticizers for polyvinyl chloride

Dimethyl and ethylene acetals of polyformylated unsaturated fatty esters were prepared, characterized, and evaluated as polyvinyl chloride plasticizers. Dimethyl acetals were prepared with trimethyl orthoformate as a water scavenger in the acid catalyzed acetalation reaction. With ethylene acetals, water was removed azeotropically. Although the acetals prepared were mixtures, molecular distillation gave diacetal esters of 80–90% purity and triacetal esters of 80–95% purity. The samples were characterized by gas liquid chromatography and by IR and NMR spectra. Compared to di-2-ethylhexyl phthalate as a plasticizer for polyvinyl chloride, the triacetal esters (both dimethyl and ethylene acetals) gave less migration and at least equivalent volatility characteristics; the triacetals also gave equivalent compatibility and strength, but somewhat less desirable low temperature and heat stability properties. The diacetal esters also had good compatibility, equivalent strength, somewhat better low temperature, but less desirable migration and volatility properties. Presented at the AOCS Meeting, Chicago, Illinois, September 1973. ARS, USDA.     

Alkyl azelaaldehydates of high purity from alkyl soyates: Preparation and properties

Reductive ozonolysis of appropriate alkyl soyates in various participating media producted methyl, ethyl,n-propyl, isopropyl andn-butyl azelaaldehydates in good yield and high purity (98+%). The participating media examined were: methyl, ethyl,n-propyl andn-butyl alcohols; mixtures of an alcohol and acetic acid; water; and mixtures of water and acetic acid. Any combination of solvent and ester, except methanol-methyl soyate, allowed good separation by fractional distillation of ester and acetal impurities from the azelaaldehydate. A preparative method was developed by which high purity ethyl azelaaldehydate is produced from soybean oil by reductive ozonolysis in water. The only major impurity by this method was ethyl hydrogen azelate, which was easily removed with a bicarbonate wash. After a single fractional distillation with a short Vigreux column, the azelaaldehydate was obtained in 78% yield and 98+% purity. Physical properties and spectral (IR, NMR and mass spectroscopy) and chromatographic data were determined for the pure alkyl azelaaldehydates. Several of these properties were also determined for acetal and diester byproducts. Presented at the AOCS-ISF Meeting, Chicago, September–October 1970.