Bromination of methyl esters of soybean fat acids and methyl linoleate with N-bromosuccinimide

1. The reaction of N-bromosuccinimide with methyl esters of soybean fat acids and with methyl linoleate has been investigated, and the influence of changes in the conditions of reaction has been studied.
2. The reaction of brominated methyl esters of soybean fat acids with sodium methoxide produced both methoxylated products and a dimer-like substance.
3. The reaction of brominated methyl esters of soybean fat acids with sodium cyanide and cuprous cyanide did not result in significant replacement of bromine with the cyano group.

     

Allylic esters of polymeric fat acids

Summary 1. Allyl, β-methallyl, and β-chlorallyl esters have been prepared from polymeric soybean fat acids by direct esterification and from dilinoleic acid by transesterification of methyl dilinoleate. 2. The method of polymerizing the esters and the properties of the polymers are described. One of the laboratories of the Bureau of Agricultural and Industrial Chemistry, Agricultural Research Administration, U. S. Department of Agriculture.     

Synthesis and isolation of methyl esters ofa-branched acids

A series of esters ofa-branched fatty acids containing 28–38 carbon atoms has been synthesized by free radical-catalyzed addition of saturated aliphatic esters to terminal aliphatic olefins. Methods of purification of methyla-decyloctadecanoate have been studied. The structure of methyla-decyloctadecanoate has been established by nuclear magnetic resonance and by independent synthesis. Presented at AOCS Meeting, Houston, April 1965. E. Utiliz. Res. Dev. Div., ARS, USDA.     

Thermoacoustic properties of methyl esters ofn-alkanoic acids

A number of thermoacoustic parameters, including the Sharma constant S₀, the isochoric temperature coefficient of volume expansivity (d Inα/d InT)_V, the isochoric temperature coefficient of internal pressure (d InP _i/d InT)_V, reduced volume V, reduced compressibility β and the Huggins parameter F, are estimated by using only the volume expansivity α from the density temperature data for a number of methyl esters ofn-alkanoic acids. The methyl esters give excellent separation of saturated fatty acid mixtures. The Sharma constant, which relates the molecular constantn and other thermoacoustic parameters, is a constant with a characteristic value of 1.11+0.01 for all these esters.     

The thiocyanogen values of the methyl esters of oleic,linoleic, and linolenic acids

Summary Thiocyanogen values were determined on the methyl esters of oleic, linoleic and linolenic acids and on six different mixtures of these esters, using 0.1 and 0.2 normal thiocyanogen solutions. The values determined with 0.1 N solutions showed less variation than those determined with 0.2 N. The composition of the mixtures calculated from equations based on the found thiocyanogen values of the esters agreed with the known composition within reasonable limits. Comparisons were made with the composition calculated with the Kaufmann-theory values. It is suggested that the F.A.C. consider adopting tentatively the values 89.4 for oleic acid, 93.9 for linoleic acid, and 162.0 for linolenic acid when 0.1 N thiocyanogen solutions are used; the values 89.4, 96.8, and 167.5 when 0.2 N solutions are employed. These represent the average of the values for these acids which have been reported in the literature. Agricultural Chemical Research Division Contribution No. 15     

Autoxidation of methyl esters of cyclopentenyl fatty acids

The early stages of the autoxidation of methyl hydnocarpate, chaulmoograte and gorlate in air have been examined at 40, 60 and 80 C, and the initial products have been compared by several methods with those derived from methyl oleate and linoleate autoxidized at 60 C. To supplement information about oxygen absorption and peroxide development in relation to time, other information about the early products, and some information about the reduced products, have been obtained by ultraviolet (UV) and infrared (IR) spectrophotometry, and by thin layer chromatography (TLC). The kinetic and other data presented in this study strongly support the conclusion that the methyl esters of cyclopentenyl fatty acids yield initial autoxidation products that, although they are primarily peroxides, differ in some ways (as expected) in the kinetics of their formation and their chemical nature, compared to those of oleate and linoleate. Nevertheless, all the data obtained strongly support the surmise that the peroxides are formed autocatalytically by a chain mechanism, and that secondary products not derived from peroxide decomposition, are formed pari passu in lesser, but increasing amounts with increasing temperature, probably from free radical intermediates. The autoxidation of esters of cyclopentenyl fatty acids has potential importance in several ways, 3 of which are mentioned briefly.     

Viscosities and densities of the methyl esters of some n-alkanoic acids

The densities and viscosities of the methyl esters of hexanoic, heptanoic, octanoic, decanoic and dodecanoic acids were determined at temperatures ranging from 10 to 80°C at 5°C intervals. The densities of the methyl esters vary linearly with temperature. When fluidities were plotted against molal volumes of the esters, smooth curves were obtained. Intrinsic volumes were determined by extrapolation to zero fluidity. Based upon Hildebrand's equation, the B values, which represent a measure of the molecules resisting transport of momentum, were calculated for each ester and found to be exponentially related to the temperatures. A modified equation relating the fluidity with temperature was formulated. Excellent agreement was obtained between calculated and experimental fluidities.     

Fatty acids,fatty alcohols,wax esters,and methyl esters fromCrambe abyssinica andLunaria annua seed oils

Crambe abyssinica andLunaria annua, members of the Cruciferae family, have seed oil glycerides containing ca. 55–65% of C₂₂ and C₂₄ unsaturated fatty acids. Fatty acids were prepared by saponification; fatty alcohols, by sodium reduction of glycerides; liquid wax esters, byp-toluenesulfonic acid-catalyzed reaction of fatty acids with fatty alcohols; and methyl esters, by reaction of fatty acids with diazomethane. Solid hydrogenated glyceride oils and wax esters were compared with several commercial waxes. Chemical and physical constants were determined for the seed oils and their derivatives. Position of unsaturation in theCrambe fatty acids was determined by gas chromatographic analysis of the permanganate-periodate degradation products. The major dicarboxylic acid was brassylic (C₁₃), proving the docosenoic acid to be erucic. Presented in part at the AOCS meeting in New Orleans, La., 1962. A laboratory of the No. Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

The effect of antioxidants in the autoxidation of methyl conjugatedcis,trans-octadecadienoates

The effect of antioxidants on the autoxidation of methyl conjugatedcis,trans-octadecadienoates was evaluated by estimating the induction period by measuring the increase in weight with time. Peroxide values and molecular weights were also used to determine extent of oxidation. UV and IR absorption were measured to determine conjugated dienes and isolatedtrans double bonds. Antioxidants, such as butylated hydroxy anisole (BHA), butylated hydroxy toluene (BHT), propyl gallate (PG) and sesamol, lengthened the induction period as much as seven to twelve times. After autoxidation to a weight gain of 10 mg per 1.5 g, the antioxidant containing samples had higher molecular weights and lower diene contents than the control samples. The induction periods were shorter, the peroxide values lower with or without antioxidants for the conjugated dienoates than for the nonconjugated dienoates. Effect of antioxidants might be explained by the formation of a hydrogen bond of the hydroxyl of the antioxidant and π-electrons as well as the inhibition of the chain-reaction.     

Stability ofd-a-tocopherol alone,in solvents,and in methyl esters of fatty acids

Summary The stability ofd-a-tocopherol in stable solvents and in methyl esters of fatty acids varied with the stability of the medium and with the concentration of tocopherol. Pure tocopherol was less stable than tocopherol in solvents. The concentrations of tocopherol that were most effective in delaying rapid oxidation of the esters were also best for stability of tocopherol itself. The rate of destruction of tocopherol could not be described by simple kinetics. N.R.C. No. 4429 Contribution from the Division of Applied Biology, National Research Laboratories, Ottawa, Canada.     

The occurrence of methyl methoxystearate isomers in the methyl esters prepared from sheep perinephric fat

A fraction has been isolated from sheep perinephric fat and identified by techniques which included mass and infrared spectrometry, as a mixture of the 8 to 14-methoxyoctadecanoic acid isomers. It is postulated that these isomers are artifacts produced by rigorous esterification with methanol and concentrated H₂SO₄ of a large sample of sheep perinephric fatty acids which are presumed to have contained trace amounts of constituent hydroxy fatty acids. It is estimated that these methoxystearic acid isomers represented approximately 0.08% of the total weight of fatty acids.     

Direct determination of saturated fatty acids in fats,oils, and methyl esters

Summary A direct gravimetric method has been developed for the determination of saturated fatty acids in fats, oils, and methyl esters. The procedure involves methanolysis of the triglycerides to produce methyl esters, followed by oxidation of the unsaturated methyl esters by potassium permanganate. The undesired, acidic oxidation products are removed by alkaline washing and the saturated methyl esters thus isolated are weighed directly. The method is intended for the determination of saturated fatty acids having C₁₆ or longer carbon chains. Small quantities of C₁₄ saturated acids will be included in the determination if present with other higher saturated acids. The method is applicable to both natural and hydrogenated vegetable oils. It is not applicable to oils containing large amounts of C₁₄ and lower saturated acids. Concentrations of saturated acids ranging from 3 to 90% in known glyceride mixtures and from 0.3 to 95% in mixtures of methyl esters were determined with an average difference from the calculated value of 0.8%. Replicate determinations on samples in the 10 to 30% saturates range gave a standard deviation of 0.3 to 0.4%. Presented at the spring meeting, American Oil Chemists’ Society, New Orleans, La., April 28 to May 1, 1957     

The amplified distillation of methyl esters of fatty acids

Summary Amplified distillation is a useful technique for the quantitative analysis of mixtures of fatty acid esters, especially for the detection and estimation of minor components and for the analysis of small samples. The amplified distillation of free fatty acids is largely limited to qualitative work on account of the formation of azeotropes with mineral oils. Presented before the 1945 Fall Meeting of the American Oil Chemists' Society, Chicago, Ill.     

Molal volumes of somen-Fatty acids and their methyl and ethyl esters

The densities of some pure methyl and ethyl esters ofn-fatty acids were determined at temperatures between 10° to 80°C. The molal volumes of these esters and the long-chain fatty acids were correlated with temperature and chainlength. The reciprocals of the average methylene contribution at long-chain and the end group contribution to the molal volumes were found to be linear functions of the temperature. With the introduction of a correction term to account for mutual interaction of the end groups, three equations, one for each of the esters and the acids, were developed. These equations were used to calculate the molal values of the acids with carbon numbers up to 30 and up to 20 for the esters at temperatures ranging from 10° to 100°C. Excellent agreements were obtained between the molal volumes calculated by the equations and those obtained from the literature and experimental data.     

Flame-ionization detector response to methyl, ethyl, propyl, and butyl esters of fatty acids

The concept of theoretical response factors is not directly applicable to methyl esters of short-chain fatty acids (FA), since their carbon deficiency is larger than expected from theory. Substituting the methyl group by an ethyl, propyl, or butyl group improved the flame-ionization efficiency of fatty acid esters gradually, up to the point where the empirical response factors of the butyl esters were identical within experimental error to the theoretical values. Butyl esters of FA have a uniform flame-ionization detection (FID) response irrespective of the number of carbon atoms contained in the FA. They exhibit a carbon deficiency of 1.0, i.e. the carbonyl carbon atom does not respond, as expected from theory. Compared to methyl esters, which have a carbon deficiency of 1.4–1.5 for short-chain FA, use of butyl esters has the advantage that a precalculation of the FID response enables the analyst to judge whether the analytical system employed works properly and the data produced are accurate and reliable. Both acid (BF₃ or H₂SO₄)-and alkali (butoxide)-catalyzed butyl ester preparation were equally effective, giving the analyst a choice of methods so that different analytical needs can be addressed efficiently. Computing response factors and comparing the theoretically expected values with those obtained experimentally gives the experimenter an indication whether the analytical system employed for FA profiling (transesterification plus the subsequent gasliquid chromatographic separation and quantitation by FID) works properly. This setup is particularly useful for an accurate analysis of the FA profile of milk fat.     

Determination of tocopherol in autoxidizing methyl esters of fatty acids

Summary Autoxidizing methyl esters of fatty acids interfered with the determination of α-tocopherol by ultraviolet spectrophotometry or by the bipyridine colorimetric method. Interference with the colorimetric method was removed by sulfuric acid treatment, but spectrophotometry was applicable only when the tocopherol was completely separated from oxidized fat. This separation could not be obtained by sulfuric acid treatment but was accomplished by room temperature saponification in an alcohol-petroleum ether system protected by pyrogallol. The sensitivity of the spectrophotometric method was increased by oxidizing tocopherol quantitatively to thep-quinone with 2N nitric acid. N. R. C. No. 4053. Presented in part at meeting of American Oil Chemists’ Society, Minneapolis, Minn., Oct. 11–13, 1954.     

Copolymerization of methyl esters of unsaturated C18 fatty acids

In order to assay the possibilities of making high polymers from linseed oil, the copolymerizations of styrene with the methyl esters of oleic, linoleic, linolenic, and conjugated linolenic acids were studied at 60–130C and copolymerizations of the last three esters with acrylonitrile were studied at 60C. Appropriate free radical initiators were employed in all cases. The esters without conjugated unsaturation show little tendency to enter a copolymer with styrene, but copolymers containing up to 40% by weight of conjugated linoleate can be obtained. Linoleic, linolenic, and conjugated linoleic esters copolymerize readily with acrylonitrile. Products containing up to 45 mole %, 80 wt %, of the conjugated ester can be made. However, methyl eleostearate, with three conjugated double bonds, inhibits the polymerization of both styrene and acrylonitrile. Quantitative comparisons of the behaviors of the esters are made through the copolymerization equation. The probable performance of these and other vinyl monomers in copolymerization with linseed oil is discussed. Presented at the Symposium on Recent Advances in Drying Oil Chemistry, Division of Organic Coatings and Plastics Chemistry, Am. Chem. Soc. meeting in Washington, 1962.