Wiederveresterung von Konzentraten mehrfach ungesättigter Fettsäuren

Reesterification of Polyunsaturated Fatty Acid Concentrates Fatty acids of the n-6 series such as γ-linolenic acid (C18:3) and of the n-3 series such as α-linolenic (C18:3), stearidonic (C18:4), eicosapentaenoic (C20:5) and docosahexaenoic acid (C22:6) are of great nutritional interest. These acids can be obtained by urea fractionation in concentrated form from natural sources like blackcurrant seed oil, borage oil, evening primrose oil, linseed oil and fish oil, respectively. Certain dietary applications require a reesterification of these fatty acid concentrates with glycerol to triglycerides. Industrial scale methods of reesterification could not be applied as such for the present polyunsaturated fatty acid systems. Therefore reaction conditions had to be adapted to these highly sensitive substances. A one step reesterification method, using ZnCl₂ as catalyst, was optimized for three different fatty acid concentrates composed of the above mentioned acids. Under the given reaction conditions, it could be observed that α-linolenic acid is much more sensitive to polymerization than γ-linolenic acid. Different purification methods of the crude triglycerides have been evaluated, obtaining best results by liquid chromatography methods, in particular with respect to decoloration of the final products.     

Zur Autoxydation ungesättigter Fettsäure-Ester in Gegenwart von Methanol und Protonen I: Die Autoxydation einfach ungesättigter Fettsäure-methylester

Autoxidation of Unsaturated Fatty Acid Esters in the Presence of Methyl Alcohol and Protons I. The Autoxidation of Monounsaturated Fatty Acid Methyl Esters The methyl esters of oleic, elaidic, 2-octadecenoic and 3-nonenoic acids were autoxidised in presence of methyl alcohol and protons. The amount of the primarily formed isomeric hydroperoxides could be estimated by the quantitative determination of the aldehydic degradation products. The acidic and the Fe⁺⁺ induced degradation of oleic acid methyl ester hydroperoxide mixture was employed for the same purpose. The α-methylene mechanism is also applicable under the conditions under which preferentially the oxygen initiated autoxidation takes place.     

Cis-trans-Isomerisierung ungesättigter Fettsäuren im Laufe der Alkydharz-Herstellung

Cis-trans Isomerisation of Unsaturated Fatty Acids during the Preparation of Alkyds We studied the influence of the preparation conditions of alkyd resins with the help of infrared spectroscopy of soya and linseed oil on the cis-trans-isomerisation of the unsaturated fatty acids present. The most important of all conditions was the temperature. The higher content of trans-isomers can be seen in the properties of alkyd resins.     

Produkte der Dimerisierung ungesättigter Fettsäuren V: Die Aromatenfraktion dimerer Fettsäuren

Products of Dimerisation of Unsaturated Fatty Acids V: The Aromatic Fraction of Dimeric Acids The aromatic fraction of dimeric fatty acid esters can be separated according to a decreasing grade of unsaturation by HPLC using an UV-recorder. Hydrogenation experiments of the collected fractions allowed the determination of the number of rings. If the aromatic fraction are oxidized with KMnO₄ using a phase-transfer catalyst benzene 1,2,4- and 1,3,5-tri-, 1,2,4,5-and 1,2,3,5-tetra- and the pentacarboxylic acid were obtained as main products. Consequently we have to conclude that the catalyst causes intramolecular extensive migration of alkyl chains. Finally 2,3-dihydrobenzofurantetracarboxylic acids with different position of the carboxylic groups were detected in the mixture of oxidation products.     

Selektivhydrierung von Fettstoffen mit metallorganischen Mischkatalysatoren nach Ziegler-Sloan-Lapporte IV: Isomerenverteilung während der Hydrierung mehrfach ungesättigter Fettsäuremethylester

Selective Hydrogenation of Fats and Derivatives Using Ziegler-Type Organometallic Catalysts IV: Distribution of Isomers during Hydrogenation of Polyunsaturated Fatty Acid Methylesters Hydrogenation of methyl linoleate using a Ziegler-type catalyst, containing nickel stearate and triethyl aluminium, proceeds mainly without previous conjugation or trans-isomerization. Both olefinic double bonds are hydrogenated with equal probability. As long as the reaction mixture contains double unsaturated esters, these compounds are inhibiting hydrogenation and isomerization of single unsaturated esters. During hydrogenation of methyl linolenate there is only less selectivity to formation of methyl linoleate. Intermediate product is a mixture of single and double unsaturated fatty acid methylesters. In the latter compounds after consumption of triple unsaturated esters both double bonds are separated by two or more methylene groups. Polyenic compounds with 1,4-position of olefinic double bonds are preferably hydrogenated than polyenic compounds with greater distance between the double bonds.     

Fraktionierung mehrfach ungesättigter Fettsäuren aus verschiedenen natürlichen Rohstoffen

Fractionation of Polyunsaturated Fatty Acids from Various Natural Oil Sources Blackcurrant seed oil, borage oil and evening primrose oil are known to be sources of γ-linolenic acid (GLA) with values of up to 25% for borage oil. These GLA concentrations are sufficient for most of the applications of these oils as such but some particular utilisations require higher concentrations of up to 70% γ-linolenic acid or more. Different fractionation techniques have been evaluated. Distillation as well as fractionated crystallization at various temperatures did not give any reasonable results. Preparative high performance liquid chromatography gives only separations on reversed phase columns of the RP 18 type. However, specific enrichment in γ-linolenic acid is obtained by urea fractionation in methanol, also with blackcurrant seed oil which contains up to 14% α-linolenic acid. On a large scale basis of around ton scale it was possible to enrich blackcurrant seed oil fatty acids to 70-80% γ-linolenic acid in a preferably 2-stage fractionation process.     

Nachweis gesättigter cycloaliphatischer und aromatischer Fettsäuremethylester durch Dünnschicht- und Gas-Chromatographie

Detection of the Methyl Esters of Saturated Cycloaliphatic and Aromatic Fatty Acids with Thin-layer and Gas Chromatography Homologous series of methyl esters of saturated cycloaliphatic (CFA) and aromatic fatty acids (AFA), which were prepared by the alkali isomerisation of fish oil followed by hydrogenation and fractionation of the cyclised mixture as well as with the help of cyclising hydrogenation, were analysed by thin-layer and gas chromatography. Even 0.4% CFA and AFA, which do not form urea-adducts, can be detected in the fractions as a substance class in thin-layer chromatography. The equivalent carbon numbers (stearic acid = 18) of the principal isomers of CFA and AFA homologues (C₁₈ to C₂₂), which were obtained as a class in the thin-layer chromatographic separation, were determined by the gas chromatography.     

Selektive Härtung mehrfach ungesättigter Fettsäuren in der Flüssigphase

Selective Hydrogenation of Multi-Unsaturated Fatty Acids in the Liquid Phase Fatty acids and esters which contain only one double bond have interesting properties such as high oxidation stability or favourable pour points. For these reasons such products find a broad field of application for instance in the sections cosmetics, textile finishing agents or oilfield chemicals. However, natural fats and oils contain often multi-unsaturated fatty acids such as linoleic and linoleinic acid which are able - even in minor amounts - to change substantially the physical and chemical properties of the fatty material. Therefore, a hydrogenation procedure is needed which enables the selective conversion of multi-unsaturated into mono-unsaturated fatty acids without formation of completely saturated compounds. After a review of the general possibilities in selective hydrogenation a new method is described to hydrogenate with solvent-stabilized palladium colloid catalysts. A remarkable high selectivity was obtained applying very mild reaction conditions. By use of the liquid-liquid two phase technique an easy and complete catalyst recycle is possible.     

Produkte der Dimerisierung ungesättigter Fettsäuren VI: Untersuchungen zur Kinetik der Bildung dimerer Fettsäuren

Products of Dimerisation of Unsaturated Fatty Acids VI: Kinetic Studies about the Formation of Dimeric Fatty Acids During the dimerisation reaction of a mixture of 60% oleic acid and 40% linoleic acid samples were collected in time intervals. The samples were converted into their dimethylates by diazomethane and separated by thin layer chromatography in one fraction of monomers and one of dimers. The monomeric fractions were further separated by GC, the dimeric fractions by HPLC. First linoleic acid reacts, either by cyclisation or by attacking another molecule of linoleic acid. Thus linoleic acid has already disappeared nearly completely at the end of the heating up period (after 60 min). The less linoleic acid is present, the more molecules of linoleic acid react with oleic acid molecules. The primary cyclic dimerisation products are slowly converted to aromatic compounds as well as cyclohexane derivatives. The oleic acid is transformed already in the heating up period into its isomer, elaidic acid and isomers thereof with double bonds in other positions of the chain. These products are converted slowly partly to stearic acid, partly to isostearic acids. Dimeric compounds of MW 592 (methylates) are produced as well by reaction of 2 molecules of oleic acid. They are slowly converted to open chain dimeric acids of MW 594 (methylates).     

Produkte der Dimerisierung ungesättigter Fettsäuren XII: Die Dimerisierung von Konjuensäure

Products of Dimerisation of Unsaturated Fatty Acids XII: The Dimerisation of Conjugated Fatty Acids Dimeric fatty acids obtained by the clay-catalyzed dimerisation of the conjugated fatty acid (mixture of 9,11-octadecadienoic acid and 10,12-octadecadienoic acid) can be separated via HPLC in form of their dimethylates in three fractions in accordance with results obtained by separation of dimeric fatty acids of linoleic acid. The first fraction of aromatic dimeric fatty acids with the molecular weight 586 mainly contains compounds with a tetrasubstituted ring system. The second fraction, consisting of alicyclic unsaturated dimeric fatty acids, is characterized by the molecular weight 590 and a cyclohexene ring system. The third fraction corresponds to alicyclic saturated dimeric fatty acids. Dimeric fatty acids resulting of a Diels-Alder-reaction were detected neither in the end products nor as products in the early phase of the dimerisation. The results obtained by the investigation of the dimerisation of conjugated fatty acids are similar to those of the dimerisation of linoleic acid. Consequently a Diels-Alder-reaction is not involved in the formation of dimeric fatty acids. Although conjugated fatty acids are predominated to undergo a Diels-Alder-reaction no such products could be detected. This result strengthens the thesis that the dimerisation of unsaturated fatty acids is initiated by a cationic mechanism. The composition of the dimeric fatty acid using conjugated fatty acids is more uniform than that of usual mixtures of linoleic and linolenic acid. This provides evidence that a modification of the educt fatty acids can yield new structures of the dimerisation products.     

Produkte der Dimerisierung ungesättigter Fettsäuren XI: Die Fraktion der alicyclischen Dimerfettsäuren

Products of Dimerisation of Unsaturated Fatty Acids XI: The Fraction of Alicyclic Dimeric Acids Dimeric fatty acids can be separated as their dimethylates by HPLC-chromatography [W. Link, G. Spiteller, Fat Sci. Technol. 92 , 135 (1990)]. The main fraction of dimeric fatty acids obtained by the dimerisation of linoleic acid consists of alicyclic unsaturated dimeric fatty acids with the molecular weights 588 and 590. The structures of these compounds remained unknown until now. This fraction was subjected to hydrogenation, epoxidation and dehydrogenation with SeO₂ and Pd/C. The investigation of the reaction products provided evidence that these dimeric acids are a mixture of the following compounds: Dimeric acids with a 6-ring and one double bond and dimeric acids with two 6-rings and a double bond could be identified. In both types of compounds the double bond can be either situated in the ring as well as outside the ring. In dimeric acids containing two rings this ring system can be condensed or separated by a C-chain. Besides dimeric acids with two 6-rings dimeric acids with one 6-ring and one 5-ring were found. Essential contributions to these deductions were obtained by an investigation of model compounds and model fractions.     

Metathese ungesättigter Fettsäureester – ein einfacher Zugang zu langkettigen Dicarbonsäuren

Metathesis of Unsaturated Fatty Acid Esters – a Simple Approach to Long-Chained Dicarboxylic Acids Long-chained, symmetric unsaturated C₁₈-, C₂₀- und C₂₆-dicarboxylic acid esters are easily accessible from natural fatty acid esters by metathesis in a two-step procedure. In the first step unsaturated fatty acid esters are cleaved by metathesis with ethylene. Pure oleic acid ester or fatty acid methylesters, produced from high-oleic sunflower oil or from rapeseed oil by transesterification with methanol, are converted to 1-decene and 9-decenoic acid methylester. From erucic acid methylester 1-decene and 13-tetradecenoic acid methylester are achieved. Using our newly developed high efficient catalytic system B₂O₃-Re₂O₇/Al₂O₃-SiO₂ + SnBu₄ conversion rates of 86 – 96% are obtained and the terminally unsaturated fatty acid esters are isolated in yields of 61 – 83%. In the second step 9-decenoic and 13-tetradecenoic acid methylester as well as 10-undecenoic methylester, which is commercially obtained by pyrolysis of ricinoleic acid ester, are converted to 9-octadecenedioic-, 13-hexacosenedioic- and 10-eicosenedioic acid dimethylester, by which process ethylene is eliminated. The conversion rates are 89 – 99% and the dicarboxylic acid dimethylesters are isolated in yields of 77 – 84%.     

Produkte der Dimerisierung ungesättigter Fettsäuren IX: Kinetische Untersuchungen zur Dimerisierung von Linolsäure

Products of the Dimerisation of Unsaturated Fatty Acids IX: Kinetic Studies about the Dimerisation of Linoleic Acid To clarify the dimerisation process of linoleic acid, we investigated samples taken in different time intervals. The first reaction step is a water addition at double bonds of the starting material and not double bond isomerisation as previously assumed. The resulting unsaturated monohydroxy fatty acids can cyclize with the second double bond in an intramolecular reaction forming 2,5-disubstituted tetrahydrofuran respectively 2,6-disubstituted tetrahydropyran derivates. Linolenic acid, present nearly always in small amounts in linoleic acid, reacts to first dimerisation products with linoleic acid by formation of a C-C-bond. The aliphatic dimers cyclize in an intramolecular reaction to mono-cyclic compounds. No dimeric acids, which would result from a Diels-Alder-reaction, could be identified. Bicyclic and aromatic dimeric acids can also be found in the early phase of the dimerisation. In the further progress of the reaction isomerisations, hydrogenations and dehydrogenations of the primary reaction products occur, thus the content of aromatic substances increases steadily.     

Metallchelate ungesättigter 1,2-Dithioäther

Metal Chelates of Unsaturated 1,2-Dithioethers The dialkyl- and diaralkyldithioethers of ethylenebisthiol (edt) and xylenedithiol form cationic 1:2 chelates with the d⁸-metal ions Ag^I and Cu^I, which have been isolated and characterized. Pd^II- and Pt^II-halides yield neutral mixed ligand complexes of the type Me (L L) X₂ (L L = dithioether, X = halogen). The dibenzyldithioether of edt is cleaved oxidatively by Cu^II and yields dibenzyldisulfide, Cu^I and an unidentified product.     

Synthese und Polymerisation ungesättigter Benzaldazine

Synthesis and Polymerization of Unsaturated Benzaldazines The preparation of methacrylic and acrylic acid derivatives of isomeric hydroxybenzaldazines and their characterization by u.v.-, i.r.-, ¹H and ¹³C n.m.r. spectroscopy are described. By radical polymerization and copolymerisation with styrene and methyl methacrylate, respectively, crosslinked polymers showing ultraviolet-absorbing properties are obtained.     

Übergangsmetallkatalysierte Oxidationen ungesättigter Fettsäuren — Synthesen von Keto- und Dicarbonsäuren

Transition-metal Catalyzed Oxidation of Unsaturated Fatty Acids — Synthesis of Ketocarboxylic Acids and Dicarboxylic Acids Terminal unsaturated C₁₀–C₁₄-fatty acid methylesters (9-decenoic-, 10-un-decenoic-, 13-tetradecenoic methylesters) were converted to methylketocarboxylic methylesters (yields: 60–75%, isolated) by oxidation with O₂/H₂O at roomtemperature under catalysis of PdCl₂/CuCl₂. Using RhCl₃/FeCl₃ at 80°C yields of 40–60% were obtained. For the first time methyl oleate was converted directly to a mixture of 9-oxo- and 10-oxo-stearic acid methylester by palladium catalyzed oxidation. In DMF/H₂O the selectivity to these two ketoesters was 85% (15% isomers), in dioxane/H₂O the selectivity droped to 55% while the yield of the oxostearic acid esters climbed to 70%. The Mn-catalyzed oxidative cleavage of methylketocarboxylic acid esters with O₂ at 115°C led in each case to a mixture of two dicarboxylic acid esters in a molar ratio of 2 : 1. Starting with 9-oxodecanoic acid azelaic and suberic acid were obtained at a conversion rate of 90%. Analogous 10-oxoundecanoic acid led to C₁₀/C₉- and 13-oxotetradecanoic acid led to C₁₃/C₁₂-dicarboxylic acids. The oxidative cleavage of 9-/10-oxostearic acid methylester yielded mixtures of C₈–C₁₀-monocarboxylic acids and methylesters of C₈–C₁₀-dicarboxylic acids.     

Veränderungen im Plasma-Lipid-Muster bei Patienten mit Neurodermitis - Beeinflussung durch Applikation ungesättigter Fettsäuren

Influence of Polyunsaturated Fatty Acids on the Plasma Phospholipids of Atopic Patients Patients with atopic eczema and a control group received evening primrose oil (EPO) for 4 weeks. In the group with atopic eczema a statistically significant improvement was observed. The baseline fatty acid composition of plasma phospholipids from the patients with atopic eczema did not differ significantly from that in the healthy subjects. After treatment the content of dihomo-γ-linolenic acid was significantly higher in the group with atopic eczema. Skin roughness decreased after treatment with EPO. Roughness was assessed by use of a stylus instrument.     

Produkte der Dimerisierung ungesättigter Fettsäuren X: Identifizierung von Estoliden in der Anfangsphase der Dimerisierung

Products of the Dimerisation of Unsaturated Fatty Acids X: Identification of Estolides in Early Phase of the Dimerisation Dimeric fatty acids, obtained by dimerisation of the conjugated fatty acid (mixture of 9,11-Octadecadienoic acid and 10,12-Octadecadienoic acid) in presence of the catalyst molybdenum pentachloride and tin dichloride, could be separated after methylation with diazomethane. The isolated fraction of methyl-9-octadecanoyloxy-octadecanoat resp. methyl-10-octadecanoyloxy-octadecanoat and methyl-9-octadec-9-enoyloxy-octadecanoat resp. methyl-10-octadec-9-enoyloxy-octadecanoat was characterized. It could be shown that these estolides can be saponified to stearic acid, oleic acid and 9- resp. 10-hydroxyoctadecanoic acid. Thus saponification can serve as an unambiguous proof of estolide components. Analogous estolides could be identified in the early phase of the clay-catalyzed dimerisation of oleic and linoleic acid. The detection of estolides shows that at low dimerisation temperature at first hydroxy fatty acids are formed which are subsequently esterified with unsaturated fatty acids. In the final products of the dimerisation estolides are absent, because their formation is suppressed by higher temperatures.     

Strukturaufklärung cyclischer Fettsäuremethylester III: Über das Auftreten bicyclischer Fettsäuremethylester in cyclisiertem Leinöl

Elucidation of Structure of Methyl Esters of Cyclic Fatty Acids III: Occurrence of Methyl Esters of Bicyclic Fatty Acids in Cyclised Linseed Oil In the study of aromatic methyl esters in alkali-cyclised linseed oil two hitherto unknown methyl esters of fatty acids were isolated by preparative gas chromatography. The structures of these compounds were elucidated by UV-, IR-, nuclear resonance and mass spectrometry and they were found to be the methyl esters of ω-(methyl-indanyl)-octanoic and ω-(ethyl-indanyl)-heptanoic acids. The indane ring system is substituted in 4,5-position.     

Über die Reduktion ungesättigter Fettsäuren und deren Ester zu ungesättigten Fettalkoholen durch selektive katalytische Hochdruckhydrierung III: Metallische und metallisch-oxidische Kupfer-Cadmium-Kontakte

Reduction of Unsaturated Fatty Acids and Their Esters to Unsaturated Fatty Alcohols by Selective Catalytic High Pressure Hydrogenation III: Metallic and Metal Oxide Copper-Chromium Catalysts Influence of catalyst composition and reaction conditions on the high pressure reduction of unsaturated fatty acids and their esters is described for metallic and mixed metal oxide copper-chromium catalysts. From these investigations and from a comparison with the efficacy of other metals in hydrogenation a hypothesis on the mechanism of the catalytic reaction in the reduction of carboxyl group and saturation of C? C double bonds is developed. The optimum reaction data of oleic acid and methyl oleate, which were used as test substances, are given.