Derivatives of ricinelaidic acid. Their infrared spectra and conformation of the ricinelaidic moiety

Summary The infrared spectra and absorptivities in the 10.3 micron region have been determined for a series of compounds in which the functional groups of ricinelaidic acid were varied systematically. The compounds investigated included ricinelaidic acid, 12-ketoelaidic acid, ricinelaidyl alcohol, and their respective methyl esters and acetates. The influence of the internal substitutents on the fundamental absorption pattern of ricinelaidic acid was determined. Observed decreases in molecular absorptivities and shifts in position of maximum absorption are related to the electron-with-drawing character of relevant substituents and to hydrogen bonding in thebeta-hydroxy-ene system. The comormation of this system is discussed. Presented at the 50th Annual Meeting, American Oil Chemists’ Society, New Orleans, La., April 20–22, 1959. One of the laboratories of the Southern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Brassidic acid: Preparation from erucic acid and mechanism of elaidinization

Brassidic acid was prepared by elaidinization of 95% erucic acid with 4 mole % nitrous acid at 70 C for 30 min, followed by crystallization from 95% ethanol. Yield was 70%, and purity was 96–97% by gas liquid chromatography and thin layer chromatography. The isomerization reaction was monitored by IRtrans absorption for optimal reaction rate and yield. There was no migration of the double bond. The NMR spectrum of thetrans protons was wide and complex with a chemical shift of 5.34 δ. The nitrous acid elaidinization, generally explained as a free radical process, is believed to be induced initially by the nitrogen dioxide anion (nitrite) and followed immediately by complex formation between the excited triplet anion and the olefin. The complex rotates to the opposite geometric configuration driven by a spin-orbital coupling process. N. Market. Nutr. Res. Div., ARS, USDA.     

Synthesis of methyl 9,12-epoxyoctadecanoate from castor oil

We report here the synthesis of methyl 9,12-epoxyoctadecanoate (2-[7-methoxycarbonyl-heptyl]-5-hexanyl-tetrahydrofuran). Methyl ricinoleate (methyl 12-hydroxy-9-cis-octadecenoate), isolated from castor oil methyl esters was isomerized with diphenyl disulfide as radical initiator under ultraviolet radiation to give thetrans isomer, methyl ricinelaidate. The latter was cyclized by slow addition of 10% bromine solution in dichloromethane to give methyl 10-bromo-9,12-epoxyoctadecanoate, which on hydrogenation with Pd/C catalyst gave the title compound, methyl 9,12-epoxyoctadecanoate.     

GLC and TLC analysis of isopropylidene derivatives of isomeric polyhydroxy acids derived from positional and geometrical isomers of unsaturated fatty acids

Gas-liquid chromatography (GLC) and thin-layer chromatography (TLC) were used to investigate the isomeric positional geometrical isopropylidene derivatives of nine isomeric dihydroxy esters, four isomeric methyl 9,10-12-trihydroxystearates, and eight isomeric methyl 9,10-12,13-tetrahydroxystearates prepared from unsaturated fatty acids. The isopropylidenes derived fromcis andtrans monounsaturated fatty acids were easily separated on both polar and nonpolar columns. Positional isopropylidenes derived from positional isomers of monounsaturated fatty acids were not separated on either liquid phase but were resolved by TLC. Four of the eight isomeric isopropylidenes derived from the four geometrical isomers of linoleic acid were resolved on the polar column; the other four isomers eluted as a single peak. The four isomeric isopropylidene-trifluoroacetate derivatives derived from ricinoleic and ricinelaidic acids were also resolved on the polar column. GLC analyses were carried out with liquid phases of ethylene glycol succinate methyl silicone polymer (EGSS-X) and methyl silicone polymer (SE-30) packed columns. Isopropylidenes, in addition to their applicability for the resolution of polyhydroxy acid mixtures, are particularly useful for the determination of double bond positions and geometrical configurations of fatty acids without cleavage. Under contract with the U. S. Atomic Energy Commission.     

The determination ofTrans isomers in GLC fractions of unsaturated esters

The determination of the amount oftrans unsaturated isomers present in collected fractions of unsaturated fatty acid methyl esters separated by gas liquid chromatography is accomplished by measuring the infrared absorbances of the collected peak at 10.36 and 8.55 μ. The ratio of these two absorbances is proportional to thetrans unsaturation. The interfering polyester column bleed is removed from the collected peaks by collection on alumina and elution into the spectrophotometer cell with CS₂.     

Methyl esters from a partially hydrogenated vegetable oil is a better infrared external standard than methyl elaidate for the measurement of totaltrans content

An infrared spectrophotometric procedure, based on the fatty acid methyl ester mixture derived from a partially hydrogenated vegetable oil as the calibration standard, has been developed for accurate analysis of the totaltrans content of hydrogenated fats. This procedure produces more accurate results than the current official methods of Association of Official Analytical Chemists and American Oil Chemists’ Society, both of which use methyl elaidate as the external standard. The results obtained with this procedure were in close agreement to those determined by the combined procedure of silver-nitrate thin-layer chromatography and capillary gas-liquid chromatography. The improved results, obtained with the partially hydrogenated vegetable oil methyl esters as the calibration standard, may be attributable to its assortment oftrans isomers, which may have different absorptivities relative to methyl elaidate.     

Determination ofcis andtrans-Octadecenoic acids in margarines by gas liquid chromatography-infrared spectrophotometry

A combined capillary gas liquid chromatography (GLC) and infrared spectrophotometry (IR) method is described for the determination ofcis andtrans-octadecenoic acids in margarines made from partially hydrogenated vegetable oils. The totaltrans-unsaturation of margarine fatty acid methyl esters determined by IR, with methyl elaidate as the external standard, was correlated to the capillary GLC weight percentages of the componenttrans fatty acid methyl esters by the mathematical formula: IRtrans=%18∶1t+0.84×%18.2t+1.74×%18∶2tt+ 0.84×%18∶3t where 0.84, 1.74 and 0.84 are the correction factors which relate the GLC weight percentages to the IRtrans-equivalents for mono-trans-octadecadienoic (18∶2t),trans, trans-octadecadienoic (18∶2tt) and mono-trans-octadecatrienoic (18∶3t) acids, respectively. This formula forms the basis for the determination of totaltrans-andcis-octadecenoic acids in partially hydrogenated vegetable oils. From the weight percentages of 18∶2t, 18∶2tt and 18∶3t determined by capillary GLC on a cyanosilicone liquid phase and the totaltrans-unsaturation by IR, the percentage of the totaltrans-octadecenoic acids (18∶1t) is calculated using the formula. The difference between the total octadecenoic acids (18∶1), determined by capillary GLC, and the 18∶1t gives the totalcis-octadecenoic acids. Presented in part at the 81st Annual Meeting of the American Oil Chemists' Society, Baltimore, Maryland, April 22–25, 1990.     

Measurement oftrans and other isomeric unsaturated fatty acids in butterand margarine

A procedure is described for gas liquid chromatographic determination of cis andtrans isomers of unsaturated fatty acids after fractionation of the saturated, monenoic, dienoic, and polyenoic fatty acid methyl esters by argentation thin layer chromatography. To test its reliability, the procedure was used for quantitative measurement of transisomers of unsaturated fatty acids in a known mixture of simple triglycerides containing saturated fatty acids from 4:0 to 24:0 andcis andtrans isomers of 14:1. 16:1, 18:1, and 18:2. Results of the analyses of five margarine and five butter samples are presented, together with results of infrared spectrophotometric analyses fortrans fatty acid concentrations, ultraviolet spectrophotometric analyses for conjugated fatty acid concentrations, and enzymatic analyses forcis-cis-methylene interrupted fatty acid concentrations. The combined argentation thin layer and gas Chromatographic procedure is suitable for determination of the principal fatty acids in complex food lipids such as milk fat.     

The application of packed column gas chromatographic analysis to the determination oftrans unsaturation

A study of the separation of synthetic mixtures ofcis andtrans methyl octadecenoate with packed column gas chromatography indicated its usefulness for such analyses. Several margarines were analyzed by this method and the results compared with those obtained by the infrared spectroscopic method. Reasonable agreement between both methods was obtained, but the gas chromatographic determination yielded lower values (average 3.8%). The presence oftrans unsaturation was also shown in selected samples of human milk and blood lipids.     

Spectral confirmation of trans monounsaturated C18 fatty acid positional isomers

The trans octadecenoic acid methyl ester isomers were obtained from a partially hydrogenated soybean oil sample and isolated by silver-ion high-performance liquid chromatography. The double bond configuration was confirmed to be trans by using gas chromatography-direct deposition-Fourier transform infrared spectroscopy. The double bond positions for nine individual trans octadecenoic acid positional isomers were confirmed by gas chromatography-electron ionization mass spectrometry after derivatization to 2-alkenyl-4,4-dimethyloxazoline. These nine trans positional isomers were resolved on either one of the two polar 100% cyanopropylpolysiloxane 100-m capillary columns, SP 2560 and Cp-Sil 88, at an isothermal temperature of 140°C. These nine isomers were confirmed to have double bonds at carbons C-8 through C-16. The pair of trans octadecenoic acid positional isomers with double bonds at C-13 and C-14 are reported for the first time to be resolved by gas chromatography. This work was presented in part at the 87th American Oil Chemists’ Society Annual Meeting in Indianapolis, IN, April 28–May 1, 1996.     

Characterization of γ-linolenic acid geometrical isomers in borage oil subjected to heat treatments (deodorization)

Heating of borage oil, either under vacuum as a model or during steam-vacuum deodorization, produces artifacts that are geometrical isomers of γ-linolenic acid (cis-6,cis-9,cis-12 18∶3 acid). In a first approach, we have studied the behavior of these fatty acids in the form of either methyl or isopropyl esters on two capillary columns (CP-Sil 88 and DB-Wax). From this study, it appears that the DB-Wax capillary column is the best suited analytical tool to study in some detail γ-linolenic acid geometrical isomers. In a second approach, the structure of these isomers was formally established by combining several analytical techniques: Argentation thin-layer chromatography, comparison of the equivalent chainlengths with those of isomers present in NO₂-isomerized borage oil on two different capillary columns, partial hydrazine reduction, oxidative ozonolysis, gas chromatography coupled with mass spectrometry and gas chromatography coupled with Fourier transform infrared spectroscopy. The two main isomers that accumulate upon heat treatments are thetrans-6,cis-9,cis-12 andcis-6,cis-9,trans-12 18∶3 acids with minor amounts ofcis-6,trans-9,cis-12 18∶3 acid. One di-trans isomer, supposed to be thetrans-6,cis-9,trans-12 18∶3 acid, is present in low although noticeable amounts in some of the heated oils. The content of these artificial fatty acids increases with increasing temperatures and duration of heating. The degree of isomerization (DI) of γ-linolenic acid is less than 1% when the oil is deodorized at 200°C for 2 h. Heating at 260°C for 5 h increases the DI up to 74%. Isomerization of γ-linolenic acid resembles that of α-linolenic (cis-9,cis-12,cis-15 18∶3) acid in several aspects: The same kinds and numbers of isomers are formed, and similar degrees of isomerization are reached when the octadecatrienoic acids are heated under identical conditions. It seems that the reactivity of a double-bondvis-à-vis cis-trans isomerization is linked to its relative position, central or external, and not to its absolute position (Δ6, 9, 12 or 15).     

13C nuclear magnetic resonance spectral confirmation of Δ6-and Δ7-trans-18:1 fatty acid methyl ester positional isomers

Trans octadecenoic acid methyl ester isomers were obtained from a partially hydrognated soybean oil and isolated by silver-ion high-performance liquid chromatography. Recently, the double-bond positions for nine individual trans octadecenoic acid positional isomers (Δ8 through Δ16) were confirmed by gas chromatography-electron ionization mass spectrometry after derivatization to 2-alkenyl-4,4-dimethyloxazoline. In this communication, the presence of two additional trans-18:1 fatty acid methyl ester positional isomers (Δ6 and Δ7) in the same mixture is confirmed by ¹³C nuclear magnetic resonance spectroscopy. The identity of the Δ5-trans-18:1 fatty acid methyl ester positional isomer is inferred. Summer student researcher.     

Optimizing Reaction Conditions for the Isomerization of Fatty Acids and Fatty Acid Methyl Esters to Their Branch Chain Products

In order to improve the oxidative stability and cold flow properties of oleic acid or methyl oleate, branch chain isomerization was conducted using a beta zeolite catalyst. Reaction conditions of temperature (200–300 °C), pressure (0.1–3.0 MPa), and co-catalyst (0–2 wt%) were optimized based on branch chain conversion and the cloud point of the ester following the isomerization reaction of oleic acid or methyl oleate. Fourier transform infrared spectroscopy (FTIR) and Gas Chromatograph equipped with Mass Spectrometry (GC/MS) analyses were used to analyze and quantify the isomerization product samples, while the cloud point of each sample was tested. The lowest and therefore, best cloud point measured was −15.2 °C at conditions of 200 °C, 3 MPa, and 2% co-catalyst using methyl oleate as a starting material. The highest branch chain conversion achieved was 50% under conditions of 300 °C, 1.5 MPa and 0% co-catalyst using oleic acid as a starting material. The use of oleic acid and methyl oleate is based on whether it is optimal to carry out the skeletal isomerization before or after the esterification reaction. Performing the isomerization reaction on the ester was preferred over the fatty acid based on the trans isomerization and cloud point results. Reducing the unbranched trans isomers was desirable in obtaining a low cloud point.     

Octadecadienoic acids of shortenings and margarines

Summary A scheme is described to separate the fatty acids of shortenings and margarines into four fractions, the final filtrate of which contains most of the polyunsaturated acids. The nature of the unsaturated acids in these fractions is discussed. It is observed that these fats contain 25–40% oftrans monoethenoic acids and 2–8% of linoleic acid and considerable proportions of both 9,12-cis, trans ortrans,cis and isolatedcis,trans isomers of linoleic acid. This work was supported in part from funds granted by the Ohio State University Research Foundation to the university for aid in fundamental research.     

Reactions of fatty materials with oxygen. XX. Recent developments in the autoxidation of methyl oleate and other monounsaturated fatty materials

Summary Some significant developments since 1947 in the autoxidation of methyl oleate and other monounsaturated fatty materials have been reviewed and critically evaluated. Subjects discussed are preparation and characterization of hydroperoxides, and mechanism, kinetics, and secondary products of autoxidation. Major developments in the field have resulted largely from the use of newer instruments (polarograph, infrared spectrophotometer) and separation techniques (urea complexes, molecular distillation, countercurrent distribution). Direct experimental evidence is now available which demonstrates that a) hydroperoxides are the predominating, but not the exclusive, primary products of autoxidation; b) the hydroperoxides obtained from methyl oleate are mostly, if not entirely,trans; c) substantially all the methyl oleate undergoes single attack in the chain before any significant amount of multiple attack occurs, and d) α,β-unsaturated carbonyl compounds are among the most important secondary products of autoxidation. Paper XIX is reference 66a. Presented at the Fall Meeting of the American Oil Chemists' Society, Philadelphia, Pa., October 10–12, 1955. A laboratory of the Eastern Utilization Research Branch, Agricultural Research Service, U. S. Department of Agriculture.     

Accurate determination oftrans isomers in shortenings and edible oils by infrared spectrophotometry

A procedure is described for the accurate analysis of thetrans content of fats and oils in the range of 0.5–36%trans. This procedure is shown to be more accurate than other current infrared spectrophotomeny methods. This increased accuracy is obtained by using a 2-component calibration standard mixture and measuring the samples as methyl esters. Good agreement between this method and the measurement oftrans content by a gas chromatography procedure is demonstrated.     

Determination of hydroperoxides and structures by high-performance liquid chromatography with post-column detection with diphenyl-1-pyrenylphosphine

A high-performance liquid chromatographic method, using post-column detection with diphenyl-1-pyrenyl-phosphine (DPPP), was developed for the quantitative and qualitative determination of isomeric lipid hydroperoxides (OOH). The OOH eluted from a normal-phase column were passed through a photodiode array detector and then mixed with DPPP solution in a reaction coil heated at 80°C. DPPP oxide formed by the reaction with OOH was determined by monitoring the fluorescence intensity at 380 nm and excitation at 352 nm. The conjugated diene OOH (13-cis, trans- and 9-cis, trans-OOH) and nonconjugated OOH (12-cis-trans- and 10-cis, trans-OOH) from photosensitized oxidation of methyl linoleate were determined in a molar ratio of 31∶29∶19∶21, respectively. However, only the two conjugated hydroperoxides were detected by ultraviolet absorption at 234 nm. Further applications were carried out for the determination of OOH of methyl oleate and methyl linolenate. This method proved to be useful for the determination of the OOH containing both conjugated and nonconjugated diene structures.     

Heat treatment of vegetable oils III. GC-MS characterization of cyclic fatty acid monomers in heated sunflower and linseed oils after total hydrogenation

Fractions of cyclic fatty acid monomers (CFAM) were isolated from linseed oil heated at 275°C for 12 hr under nitrogen, at 240°C for 10 hr under nitrogen and at 240°C for 10 hr under air. Cyclic fatty acid monomers fractions were also isolated from a sunflower oil heated at 275°C for 12 hr under nitrogen and at 200°C for 48 hr in a commercial fryer. The CFAM fractions were hydrogenated and their composition studied by gas liquid chromatography coupled with mass spectrometry (GC-MS). The CFAM in the fraction isolated from heated linseed oil samples were a mixture (1:1) ofcis andtrans cyclopentyl and cyclohexyl isomers, while the CFAM in the fractions isolated from heated sunflower oils were mostly cyclopentyl isomers. The major cyclopentyl isomers weretrans andcis methyl 7-(2′-hexylcyclopentyl) -heptanoate, methyl 9-(2′-butyl-cyclopentyl)-nonanoate and methyl 10-(2′-propylcyclo-pentyl)-decanoate. The major cyclohexyl isomers were thetrans andcis methyl 9-(2′-propylcyclohexyl)-nonanoate which represented about 50% of the CFAM isomers isolated from heated linseed oil samples. For part II in this series see Ref. 1.     

Lack of regioselectivity in formation of oxohydroxyoctadecenoic acids from the 9- or 13-hydroperoxide of linoleic acid

Either 9-hydroperoxy-trans-10,cis-12-octadecadienoic acid or 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid was treated with the catalyst, cysteine-FeCl₃, in the presence of oxygen. Oxohydroxyoctadecenoic acids were among the many products formed as a result of hydroperoxide decomposition. A mixture of 9(13)-oxo-13(9)-hydroxy-trans-11(10)-octadecenoic acids (δ-ketols) was produced from either isomeric hydroperoxide. The formation of isomeric δ-ketols from 9-hydroxy-trans-12,13-epoxy-trans-10-octadecenoic acid (epoxyol), a known product of 13-hydroperoxy-cis-9,trans-11-octadecadienoic acid decomposition, implies that the epoxyol is an intermediate. The mechanism was elucidated by the facile conversion of the epoxyol (methyl ester_ to methyl 9(13)-oxo-13(9)-hydroxy-trans-11(10)-octadecenoates with a Lewis acid, BF₃-etherate. Presented at the 14th World Congress, International Society for Fat Research, Brighton, U.K., September 17–22, 1978. The mention of firm names or trade products does not imply that they are endorsed or recomended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Vicinally unsaturated hydroxy acids in seed oils

Summary The interference of certain unsaturated hydroxy acids in the Durbetaki method of epoxide determination has been demonstrated. The concentrations of these constituents were determined concurrently with those of epoxy components by measurement of the near infrared spectra of samples before and after treatment with anhydrous ethereal hydrogen chloride. The individual hydroxy esters were separated and isolated from samples of mixed esters by thinlayer chromatography. GLC of these esters resulted in their alteration to conjugated trienoates and gave proof of their conjugated diene hydroxyl structure. Thin-layer chromatographic and infrared studies verified theTrans-trans diene unsaturation of the acid fromDimorphotheca aurantiaca oil and showed that the other hydroxy compounds examined have acistrans diene system. These data suggest that the seed oils ofArtemisia absinthium, Calliandra eriophylla, Balanites aegyptica, Cosmos bipinnatus, and Helianthus annuus contain 9-hydroxy-trans-10-cis-12- and 13-hydroxy-cis-9-trans-11-octadecadienoic acids. Supported by grants from The Hormel Foundation and the National Institutes of Health (Research Grant No. H-3559), and presented in part at the 33rd fall meeting, American Oil Chemists’ Society, Los Angeles, Calif., September 28–30, 1959. Fulbright Scholar to the Hormel Institute, 1958–1960.