Cyclic fatty acids: Separation from straight-chain fatty acids by urea adducting

A mixture containing 37% cyclic and 63% straight-chain fatty acids, made by high-temperature treatment of linseed oil fatty acids with alkali, was separated by the urea adduct method to give unsaturated cyclic fatty acids (nonadduct) in 95% purity and 90–95% yeild. Previous reports from this Laboratory describe a process for separating cyclic fatty acids from stearic acid by hydrogenation followed by crystallization at −40C. The urea adduct method avoids hydrogenation and low-temperature crystallization, and furthermore, unsaturated cyclic and unsaturated straight-chain products can be recovered as individual fractions. Then, by readducting the unsaturated straight-chain fatty acid fraction, the small amounts of palmitic and stearic acids are removed leaving an unsaturated fraction containing oleic, nonconjugated and conjugated linoleic and some unsaturated cyclic fatty acids. Presented at AOCS Meeting, Los Angeles, April 1966. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Cyclic fatty acids from linolenic acid

Linolenic acid of 95% purity was heated with excess alkali in ethylene glycol to produce cyclic fatty acids. Reaction variables, which are associated with the cyclization reaction and which were investigated, included solvent-to-fatty-acid ratio, catalyst concentration, and reaction temperature, headspace gas (N₂ or C₂H₄), and head-space gas pressure. Yields of cyclic acids were improved by increasing solvent ratio (1.5–6 wt basis), reaction temperature (225–295C), and catalyst concentration (10–100% excess). With nitrogen the optimum catalyst concentration was about 100% excess, but when ethylene was used, no increase was obtained beyond 50% excess catalyst. Yields of polymeric acids produced in the reaction generally decreased as cyclic acid yields increased, except in one instance. Higher yields of cyclic fatty acids were obtained with ethylene than with nitrogen under all comparable conditions, and increasing the ethylene pressure to as high as 500 psi improved the yield. Ethylene adds to the conjugated double bonds and is believed to give C₂₀ fatty acids having a 1,4-disubstituted monoene ring in the chain. The maximum yield of monomeric cyclic acids from 95% linolenic acid was 84.6%, the balance being polymeric and unreacted monomeric acids. Monomeric acids from this test contained 95% cyclic acids. Presented at AOCS meeting, New Orleans, 1962. No. Utiliz. Res. & Dev. Div., ARS, U.S.D.A.     

Homogeneously catalysed hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols

The use of copper and cadmium oxides or soaps as catalysts for the hydrogenation of unsaturated fatty acids to unsaturated fatty alcohols has been investigated. It is shown that copper soaps homogeneously activate hydrogen. When copper and cadmium oxides are used as catalysts, they react with the acid under formation of a homogeneous soap solution. A continuous reaction system for the preparation of unsaturated fatty alcohols by hydrogenation under the influence of copper and cadmium soaps is described.     

The isomerization of fats during hydrogenation and the metabolism of the component fatty acids

Summary Extensive positional and geometrical isomerization occurs during the catalytic hydrogenation of edible oils and fats. The extent of this isomerization can be controlled by varying the conditions of hydrogenation. Studies on the nutritional and metabolic aspects of the geometric isomers formed during the hydrogenation of edible fats indicate that the animal organism appears to be capable of metabolizingrans isomers. However there is some evidence to indicate that the deposition oftrans fatty acids in animal tissues may worsen a pre-existing essential fatty acid deficiency. Presented at the 32nd fall meeting, American Oil Chemists' Society, October 20–22, 1958, Chicago, Ill.     

Alteration of long chain fatty acids of herring oil during hydrogenation on nickel catalyst

During hydrogenation of a refined herring(Clupea harengus) oil iodine value (IV) 119, on a commercial nickel catalyst, samples were collected at IV 108, 101, 88 and 79. In the early stages of the process, IV 119 to IV 101, the positional and geometrical isomerization of the long chain monoenoic fatty acids (20:1 and 22:1) was hindered by the stronger absorption on the catalyst surface of the polyenes with 4, 5 and 6 double bonds. Consequently at IV 101, 70% of these polyenes had been converted to dienoic and trienoic fatty acids, but only 3-4%trans 20:1 and 22:1 accumulated. As the hydrogenation proceeded, IV 101 to IV 79, the originaleis 20:1 and 22:1 isomers (mainly Δ11 with some ΔA9 and Δ13) decreased and new positional and geometrical isomers (both cis andtrans in positions Δ6 to Δ15) were formed. The majortrans isomers were Δ11 accompanied by important proportions of Δ10 and Δ12. At IV 79, moretrans 20:1 (ca. 36%) thantrans 22:1 (ca. 29%) was detected. Monoethylenic fatty acids newly formed from polyethylenic fatty acids made only minor contributions to the total 20:1 and 22:1 at these levels of hydrogenation, but a “memory effect” which skews the proportions of minorcis andtrans isomers can be attributed to the proportions of minorcis 22:1 isomers (Δ9, Δ13 and Δ15) orginally present. Presented in part at AOCS Annual Conference, San Francisco, May 1979.     

Selective hydrogenation of fatty acids and methyl esters of fatty acids to obtain fatty alcohols–a review

In this paper, a review is presented of the evolution of different catalytic systems and operating conditions used in the selective hydrogenation of acids and esters of fatty acids to obtain fatty alcohols, which have broad industrial applications in the oleochemical industry. In addition, the current status of the different technologies used industrially (Lurgi, Davy and Henkel) for obtaining fatty alcohols, as well as major global sources of raw materials for the oleochemical industry are put forward. Finally, the reaction mechanisms of the selective hydrogenation process of oleic acid and methyl oleate to obtain the corresponding unsaturated alcohol as well as the new catalysts proposed by researchers are described. © 2016 Society of Chemical Industry     

Cyclic fatty acids in sunflower oils during frying of frozen foods with oil replenishment

Frying of frozen foods has become popular because it considerably reduces cooking time. Polymers and cyclic fatty acid monomers (CFAM) formed during frying are potentially toxic and therefore their production should be minimized. Twenty discontinuous fryings of different frozen foods were carried out over ten consecutive days, in sunflower oil (SO) and in high‐oleic acid sunflower oil (HOSO), by adding fresh oil after each frying to bring the volume of the fryer oil back to 3 L. CFAM methyl ester derivates were hydrogenated, isolated, concentrated and quantified by HPLC using a reverse‐phase column, followed by gas chromatography. After 20 fryings, significantly higher contents of polar material, polymers and CFAM (all p <0.001) were found in SO than in HOSO. Bicyclic compound formation was four times higher in SO (p <0.001). The fat from the fried potatoes presented a polymer content very similar to that of their corresponding oils. The 100‐g rations of the SO‐fried potatoes from the 20^th frying supply 49 or 15%, respectively, more polymers and CFAM and 1 mg more bicyclic fatty acids than the 100‐g rations of HOSO‐fried potatoes. Because digestion and absorption of polar material, polymers and CFAM occur, the data clearly show the advantageousness and advisability of frying with HOSO rather than SO.     

Positional isomers formed during the hydrogenation of cottonseed oil

Summary A commercial cottonseed oil was hydrogenated under nonselective, normal, and selective conditions. The operating variables used were within the ranges of those ordinarily found in large-scale operations. For each run samples were withdrawn at iodine values of approximately 75, 62, and 48; and these samples were analyzed for the position of the donble bonds, content oftrans isomers, and content of linoleins. Double bonds were found in the 6 through 14 positions of the monounsaturated fatty acid groups resulting from the hydrogenations. On the basis of the percentage distribution of the double bonds, there appeared to be no marked tendency for the linoleoyl group to form 9- or 12-isomers of the oleoyl group. In the early stages of the selective hydrogenation the rate at which double bonds shifted from the 9-position was greater than the rate at which double bonds were hydrogenated. The conditions of hydrogenation did not have a marked effect on the distribution of the double bonds at iodine values of about 62 and 48. The conditions of hydrogenation did have a marked effect on the percentage oftrans bonds. At an iodine value of approximately 75 the content oftrans bonds, expressed as weight percentage of trielaidin, was 9.4 for the nonselective hydrogenation and 27.3 for the selective hydrogenation while at an iodine value of approximately 48 these values increased to 21.6 and 37.7, respectively. Presented at the 48th Annual Meeting. American Oil Chemists' Society, New Orleans, La., April 29–May 1, 1957. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Menzation of mono ethenoid acids during hydrogenation

Methyl petroselinate, methyl oleate, and methyl erucate were hydrogenated under conditions used in industry for selective hydrogenation. The resulting products were separated into saturated esters andtrans- and cis-unsaturated esters on a silver nitrate impregnated silicic acid column. The positional isomers in the total hydrogenated samples and the cis andtrans-fractions were determined by oxidation with permanganate-per-iodate and GLC analysis of the resulting di-carboxylic fragments. Positional isomers were found in bothtrans andcis-fractions with equal shifting of the bond toward and away from the carboxyl group, regardless of whether the bond was originally in the 6,9, or 13 position. The ratio oftrans tocis-form in the positional isomers in all cases was higher than the reported equilibrium proportions of 2:1.     

The hydrogenation of dietary unsaturated fatty acids by the ruminant

Summary Goats were fed alfalfa meal containing 10% cottonseed or linseed oil. After 11 weeks the fatty acids of rumen, stomach, and caecum contents were compared to those of the feed. It was found that the high levels of linoleic and linolenic acis of the feed were reduced to very low levels in the rumen, with comparable increases in the saturated acids. Monoethenoid acids were increased after linseed oil ingestion and in one animal after cottonseed oil ingestion. The ratio of monoethenoid to saturated acids in the rumen fat was lower than in the endogenous fat of nonruminant animals. This explains the paradox of the low ratio in the depot fat of ruminants even after the ingestion of highly unsaturated fats. Supported, in part, by a grant from the Office of Naval Research. Scholar of the government of Mysore, India.     

Reactivity of fatty acids in the different positions of the triglycerides during hydrogenation of canola oil

Canola oil was hydrogenated under selective and nonselective conditions. After various hydrogenation times, the triglycerides were hydrolyzed by pancreatic lipase and the monoglycerides separated by TLC. Triglycerides and monoglycerides were analyzed for fatty acid composition andtrans isomer content. The reaction rate in the 2- and 1,3-positions of the glycerides was identical and of first order kinetics. Since the 2-position of the canola oil contained higher levels of 18:2 acids, the rate of change was greater than in the 1,3-positions. There were indications of a slightly lower rate oftrans formation in the 2-position during nonselective hydrogenation. Linoleate selectivities for the 2- and 1,3-positions were determined.     

New cyclopentenone fatty acids formed from linoleic and linolenic acids in potato

[1-¹⁴C]Linoleic acid was incubated with a whole homogenate preparation from potato stolons. The reaction product contained four major labeled compounds, i.e., the α-ketol 9-hydroxy-10-oxo-12(Z)-octadecenoic acid (59%), the epoxy alcohol 10(S),11(S)-epoxy-9(S)-hydroxy-12(Z)-octadecenoic acid (19%), the divinyl ether colneleic acid (3%), and a new cyclopentenone (13%). The structure of the last-mentioned compound was determined by chemical and spectral methods to be 2-oxo-5-pentyl-3-cyclopentene-1-octanoic acid (trivial name, 10-oxo-11-phytoenoic acid). Steric analysis demonstrated that the relative configuration of the two side chains attached to the five-membered ring was cis, and that the compound was a racemate comprising equal parts of the 9(R), 13(R) and 9(S), 13(S) enantiomers. Experiments in which specific trapping products of the two intermediates 9(S)-hydroperoxy-10(E), 12(Z)-octadecadienoic acid and 9(S), 10-epoxy-10, 12(Z)-octadecadienoic acid were isolated and characterized demonstrated the presence of 9-lipoxygenase and allene oxide synthase activities in the tissue preparation used. The allene oxide generated from linoleic acid by action of these enzymes was further converted into the cyclopentenone and α-ketol products by cyclization and hydrolysis, respectively. Incubation of [1-¹⁴C]linolenic acid with the preparation of potato stolons afforded 2-oxo-5-[2′(Z)-pentenyl]-3-cyclopentene-1-octanoic acid (trivial name, 10-oxo-11, 15(Z)-phytodienoic acid), i.e., an isomer of the jasmonate precursor 12-oxo-10, 15(Z)-phytodienoic acid. Quantitative determination of 10-oxo-11-phytoenoic acid in linoleic acid-supplied homogenates of different parts of the potato plant showed high levels in roots and stolons, lower levels in developing tubers, and no detectable levels in leaves.     

Selective hydrogenation with copper catalysts: I. Isolation and identification of isomers formed during hydrogenation of linolenate

Methyl linolenate was hydrogenated with 10% copper chromite catalyst at 150 C and atmospheric hydrogen pressure. The product was separated into monoene, diene and triene fractions by countercurrent distribution. These fractions were further separated into various geometrical isomers. The double bond location in the various fractions was determined by reductive ozonolysis. Double bonds in bothcis andtrans monoene fractions, as well as incis,trans andtrans,trans conjugated dienes, were extensively isomerized. A monoene containing vinylic unsaturation was one of the major products. The nonconjugated dienes were mostly dienes whose double bonds were widely separated. Results are explained on the basis of conjugation of the double bonds in linolenate followed by hydrogen addition. Presented in part at the symposium “Hydrogenation Process,” Division of Industrial Engineering Chemistry, 157th American Chemical Society Meeting, Minneapolis, April 1968. No. Utiliz. Res. Dev. Div., ARS, USDA.     

Improved ozonolysis method for analysis of total n−3 fatty acids during hydrogenation of fish oils

A rapid and precise method for determining the total amount of n−3 fatty acids in small samples of fish oil is presented. The oil is ozonized at −10°C in hexane solution, and the ozonides are subsequently reduced with triphenyl-phosphine at 40°C. The propanal formed is quantitated by capillary gas chromatography. The method was utilized to follow the industrial hydrogenation of a fish oil, and it was demonstrated that the n−3 double bonds were simultaneously reduced to one-sixth as the iodine value decreased to one-half.     

Protection of dietary polyunsaturated fatty acids against microbial hydrogenation in ruminants

Polyunsaturated fatty acids are normally hydrogenated by microorganisms in the rumen. Because of this hydrogenation ruminant triglycerides contain very low proportions of polyunsaturated fatty acids. A new process is described whereby polyunsaturated oil droplets are protected from ruminal hydrogenation by encapsulation with formaldehyde-treated protein. The formaldehyde-treated protein resists breakdown in the rumen thereby protecting the fatty acids against microbial hydrogenation. When these protected oils are fed to ruminants the formaldehydeprotein complex is hydrolyzed in the acidic conditions of the abomasum and the fatty acids are absorbed from the small intestine. This results in substantial changes in the triglycerides of plasma, milk and depot fats, in which the proportion of polyunsaturated fatty acids is increased from 2–5% to 20–30%. These effects are observed in the plasma and milk within 24–48 hr of feeding while a longer period is necessary to alter the composition of sheep depot fat. The implications of these findings are discussed in relation to human and ruminant nutrition.     

Reactions of conjugated fatty acids. VIII. Dibasic acids by hydrogenation and oxidative cleavage

Summary Conjugated linoleic acid can be hydrogenated as sodium soap in an aqueous or ethylene glycol solution with commercial nickel catalysts. Under suitable conditions the acid is reduced predominantly to monounsaturated acids with only a slight increase in saturated acids. An alkali-conjugation reaction mixture may be hydrogenated without isolating the conjugated acids. One set of conditions found suitable for hydrogenation is as follows: 10 g. of conjugated linoleic acid, 7 g. of sodium hydroxide, 250 ml. of water, and 0.05 g. of nickel placed under 40 p.s.i. hydrogen pressure and heated at 140°C. for 1 hour. Acids prepared from this reaction mixture have an iodine value of about 90. Oxidation and chromatographic analyses of the resultant dibasic acids indicate that with alkali-conjugated linoleic acid, 1,2, 1,4, and 3,4 addition of hydrogen take place with equal ease. The reduced acids contain 66%trans acids. Withtrans,trans conjugated linoleic acid, 1,4 addition takes place to a greater extent that 1,2 and 3,4 addition, and the reduced acids are allrans. Presented at the fall meeting, American Oil Chemists' Society, Cincinnati, O., September 30–October 2, 1957. Part VII is in press, Journal of Organic Chemistry.     

Cyclic fatty acid monomers and thermoxidative alteration compounds formed during frying of frozen foods in extra virgin olive oil

The measurement of polar content and specific polar compound distribution was used to evaluate the alteration of an extra virgin olive oil (EVO) used 20 times to fry frozen foods employing two methods of frying (with or without oil replenishment during frying). In addition, cyclic fatty acid monomers (CFAM) were quantified and identified throughout the 20 frying operations. Total polar content and specific polar compounds increased in the used oil (with or without replenishment). Nevertheless, frequent replenishment (FR) permits a higher number of fryings because of a dilution effect that helps maintain lower amounts of polar and specific alteration compounds than when null replenishment (NR) was used. CFAM were absent in the unused EVO, but appeared in the oil bath as a consequence of oil heating. The total CFAM concentration was higher when the oil was used with the NR method. Cyclopentyl fatty acids were more abundant than cyclohexyl ones. The data suggested that the FR frying is more appropriate to maintain the quality of the oil during frozen food frying.     

Two-step homogeneous conjugation and hydrogenation of methyl esters of unsaturated fatty acids

A new approach to the selective hydrogenation of unsaturated fatty acids is suggested. It consists of a two step process. The first is a selective conjugation of the double bonds, while the second consists of the hydrogenation reaction using a catalyst which is specific to conjugated systems. Potassiumt-butoxide was used as a conjugation catalyst and its activity and selectivity were tested at various concentrations, different molar ratios of catalyst to oil, and in various solvents. Phenanthrene chromium tricarbonyl was used as the hydrogenation catalyst and its activity tested at various concentrations, temperatures and in various solvents. UN Expert, Physical Organic Chemist.