Products formed by photosensitized oxidation of unsaturated fatty acid esters

Photosensitized oxidation of unsaturated fatty acid methyl ester was carried out using methylene blue as a sensitizer. Oxidation products, monohydro-peroxides, were identified as trimethylsilyl derivatives. Methyl oleate gave the 9- and 10-isomers; methyl linoleate, the 9-, 10-, 12-, and 13-isomers; and methyl linolenate, the 9-, 10-, 12-, 13-, 15-, and 16-isomers, respectively. The double bond to which the hydroperoxide group attached was shifted to the adjacent position in each isomer. Thus, both conjugated and nonconjugated isomers were present in methyl linoleate monohydroperoxides and methyl linolenate monohydroperoxides. By the inhibition experiment, it was ascertained that the above reaction proceeded via singlet oxygen. The relative rates of methyl oleate, methyl linoleate, and methyl linolenate were 1.0∶1.7∶2.3, respectively. These results obtained from the methyl esters were applied to the photosensitized oxidation of triglycerides purified from vegetable oils, and the reaction mechanism on triglycerides was proposed.     

The enzymatic hydrolysis and tissue oxidation of fatty acid esters of sucrose

Summary Various preparations of sucrose fatty acid esters were hydrolyzed by wheat germ or pancreatic lipase, pancreatin, pancreatic juice, α-amylase, invertase, or liver homogenates to yield sucrose and free fatty acids as products. The greatest activity was observed with the liver homogenate. None of the enzymes studied cleaved the glycosidic linkage as indicated by the lack of appearance of reducing groups and by paper chromatography of the products. The greatest hydrolysis by pancreatic lipase was observed with sucrose esters having a greater preponderance of unsaturated fatty acids, namely, sucrose trilinoleate, sucrose dilinoleate, sucrose tetralinoleate, and “Sequol 260” (69% unsaturated fatty acids). Sodium taurocholate was required for hydrolysis by pancreatic lipase but not by wheat germ lipase. Sucrose ester was inhibitory to the hydrolysis of triolein by all lipolytic preparations. Tetra-ethyl pyrophosphate and cupric ions were not inhibitory to the hydrolysis of sucrose ester. Sucrose fatty acid esters supported respiration by rat liver homogenates and to a much lesser extent by rat intestinal mucosa. The rate of oxidation was greater than that observed with sucrose and the corresponding fatty acid. The greatest activity was observed with esters of fatty acids having a greater preponderance of unsaturated fatty acids, namely, “Sequol 260,” sucrose di-, tri-, and tetralinoleate. This work was carried out under U.S.P.H.S. Grant No. A-1808 and Sugar Research Foundation Grant No. 109.     

Thermal oxidation of lipids in monolayers II. Unsaturated fatty acid esters

To investigate whether oxidation of lipids in the ordered state differs from that in the bulk phase upon heating, ethyl oleate, ethyl linoleate and ethyl linolenate adsorbed as monolayers on silica were used as model systems. For both bulk and monolayer samples, the major decomposition products found were those typical of classical decomposition of hydroperoxides. However, quantitative and qualitative differences were observed after heating. The decomposition patterns in monolayers were much simpler than those of the bulk samples. The major decomposition products of the substrates in monolayers were ethyl 9-oxononanoate and nonanal from ethyl oleate, ethyl 9-oxononanoate and hexanal from ethyl linoleate, and ethyl 9-oxononanoate and hexenal from ethyl linolenate. It is likely that the acidic nature of silica favored a selective heterolytic cleavage of hydroperoxide intermediates.     

Partition coefficients for fatty acid esters in supercritical fluid CO2 with and without ethanol

The complex nature of fish oils was exploited to study the dependence of structural factors upon fatty acid ester solubility in supercritical fluid carbon dioxide (SCF-CO₂). Partition coefficients were determined for a number of components present in two mixtures of fatty cid ethyl esters derived from menhaden oil in SCF-CO₂ at 60°C and 125 bar. Analogous data also were obtained for SCF-CO₂ with 5% (w/w) ethanol added. The addition of ethanol was found to increase partition coefficients for all species, but resulted in a decrease of fluid selectivity. Aside from the chain length of a component, both the degree and position of unsaturation were found to be structural factors that affect the value of the partition coefficient.     

Cis-Trans isomerization of unsaturated fatty acid methyl esters without double bond migration

Trans isomerization of monoenoic and dienoic fatty acid methyl esters has been carried out with thiols and diphenylphosphine in the presence of azobisisobutylnitrile. The equilibrium mixture contained 75–80%trans double bonds and there was no migration of the double bonds.     

Metathesis of fatty acid esters

In metathesis reactions, unsaturated compounds are converted into new compounds via an exchange of alkylidene groups: 2 RCH=CHR′⇌RCH=CHR+R′CH=CHR′ Since its discovery in 1964, this catalytic reaction has found several large-scale applications in petrochemistry. One of the most promising synthetic applications of metathesis is to functionalized olefins such as unsaturated esters, ethers, amines, etc., because this allows single-step syntheses of a variety of mono- and difunctional hydrocarbon derivatives. Unfortunately, however, most metathesis catalysts are easily poisoned by polar groups. In 1972 in our institute, the WCl₆-(CH₃)₄Sn system was found to be effective as a catalyst for monogeneous metathesis of fatty acid esters. Thus methyl oleate was converted into 9-octadecene and dimethyl 9-octadecene dioate, starting materials for the synthesis of valuable chemical products. In 1977 we developed a heterogeneous catalyst system: Re₂O₇ on Al₂O₃, activated with a small amout of (CH₃)₄Sn. Systematic research has led to intersting applications of metathesis and cometathesis reactions with these catalysts. An example is the cometathesis of methyl oleate with ethene, to produce shorter-chain compounds with terminal double bonds: CH₃(CH₂)₇CH=CH(CH₂)₇COOCH₃+CH₂=CH₂⇌CH₂=CH(CH₂)₇CH₃+CH₂=CH(CH₂)₇COOCH₃ Cometathesis of olive oil (mainly triolein) with ethene opens the possibility of producing both α-olefins in the C₁₀ range and fatty oils with lower molecular weight (palm oil type). Until now, metathesis of fatty esters has been restricted mainly to synthetic purposes. Large-scale applications depend mainly on the development of more active and cheaper catalyst systems.     

Photo-sensitized oxidation of unsaturated fatty acid methyl esters. The identification of different pathways

The photo-sensitized oxidation of methyl linolenate and methyl oleate was studied using erythrosine and riboflavin as sensitizers. The complex mixtures of hydroperoxides obtained were analyzed for the proportion of conjugated products and, after reduction to the corresponding mixtures of hydroxystearates, for the distribution of positional isomers. By comparing the mixtures with that obtained from autoxidation, it was shown that the riboflavin reaction involved the “Type 1” mechanism of photosensitized oxidation which proceded via the formation of diene-radicals and yielded the same positional isomers of hydroperoxides as autoxidation. Thus, mixtures of the 8, 9, 10, and 11 positional isomers of allylic hydroperoxides were formed from oleate and the 9, 12, 13, and 16 isomers of conjugated diene-hydroperoxides from linolenate oxidation. The erythrosine reaction, on the other hand, proceded via the “Type 2”. mechanism which involved singlet oxygen as the oxygenating species. The mixtures of isomers resulting from oxidation involving singlet oxygen were different from those obtained by autoxidation. Oleate oxidation gave rise to a mixture of only the 9 and 10 positional isomers while the mixture obtained from oxidation of methyl linolenate contained non-conjugated hydroperoxide isomers (with the hydroperoxide group at positions 10 and 15) as well as the conjugated—9, 12, 13, and 16—isomers.     

脂肪酸酯的技术与市场发展动向

论述了脂肪酸一元醇酯,多元醇酯的特性、合成及用途,并介绍了由脂肪酸酯开发“绿色”表面活性剂的最新技术动向。     

The rates of oxidation of unsaturated fatty acids and esters

The rates of autoxidation of oleic acid, ethyl oleate, linoleic acid, 10,12-linoleic acid, ethyl linoleate, trilinolein, pentaerythritol linoleate, dipentaerythritol linoleate, elaidolinolenic acid, linolenic acid, ethyl linolenate, trilinolenin, and methyl arachidonate have been studied by oxygen uptake in a Warburg respirometer and the results are compared with the rates of enzymatic oxidation of lipoxidase substrates. The increase in the number of double bonds in a fatty acid by one increases the rate of oxidation of the fatty acid or its esters by at least a factor or two. Earlier findings that acids oxidize more rapidly than their esters have been confirmed. The initial rates of lipoxidase oxidation of ethyl linoleate, ethyl linolenate, and methyl arachidonate were found to be essentially the same.     

Enzymatic synthesis of wax esters from rapeseed fatty acid methyl esters and a fatty alcohol

Wax esters were transesterified from fatty acid methyl esters of rapeseed and a fatty alcohol (1-hexadecanol, 16:0). The amounts of both the substrates were fixed to 0.1 mmol and an immobilized enzyme, Lipozyme, was used as catalyst. The experiment was performed following a statistic central composite design with five variables. The enzyme/lipid ratio was varied between 0.3–0.9 of the substrate weight and the enzyme was equilibrated to different water activities varying from 0.11 to 0.44. A temperature range of 50–80°C was investigated and the reaction time lasted up to 40 min. A solvent, isooctane, constituted 0–30% of the substrate weight. The first experimental series was performed in small closed test tubes. In the second series the caps of the test tubes were off to evaporate the methanol produced during the reaction. The highest initial reaction rate was 9.6 g_{wax esters}/g_enzyme · h. It appeared when: the enzyme/lipid ratio was low, 0.3, the temperature was high, 80°C; no isooctane was present; and the water activity was below 0.11. The initial reaction rate was independent of the caps on the test tubes. With the large amount of enzyme the yield of wax esters was above 70% after 10 min in both experimental series. In the reaction with caps, the reaction reached equilibrium at 83% after 20 min at 80°C. However, without caps the continuous evaporation of methanol increased the equilibrium constantly, and after 40 min at 80°C a yield of 90% was reached.     

Vesicles from sucrose fatty acid esters

It has been confirmed, from observations with an electron microscope after staining negatively with aqueous uranyl acetate solutions and using a flourescent microscope, that sucrose fatty acid esters form closed vesicles. The range of particle size of the vesicle, consisting of chromatographically fractionated sucrose dilaurate, was apparently 70–700 nm in the longer diameter of individual vesicles based on the transmission electron microscopic (TEM) observation. The weight-average particle size was 424 nm as shown by means of the photon-correlation method. The amounts of 6-carboxyfluorescein trapped in the vesicles of sucrose fatty acid esters were determined, and it was ascertained that the volumes of the central water phase depended upon the acyl chain lengths of fatty acid residues. Further, the effect of the additives [cholesterol and dicetyl phosphate (DCP) was examined. As an example, the vesicle of sucrose stearate had a central water phase of 1.7 one water/mol ester, and showed a slow release of 6-carboxyfluorescein from the central water phase after preparation of the vesicle.     

脂肪酸淀粉酯的合成与结构表征

脂肪酸淀粉酯是一种新型的非离子型表面活性剂,具有广泛的应用价值.以天然的淀粉和大豆油为原料,通过化学法进行酯化改性,制得混合脂肪酸淀粉酯.研究了基本的合成路线,并用FT-IR和UV对其结构进行表征.产物乳化性能比较优越.     

Performance of sulfoxylated fatty acid methyl esters

Sulfoxidation of fatty acid methyl esters with SO₂, O₂, and ultraviolet light of appropriate wavelength has led to the synthesis of methyl esters sulfonates or sulfoxylates known as Φ-MES because of the possible random position of SO₃ group in the alkyl chain. This work describes experimental measurements of physical properties such as solubility and viscosity of sodium Φ-MES water solutions. Amphipathic properties such as surface tension, critical micelle concentration, wetting and foaming powers were measured as well and compared to linear alkylbenzene sodium sulfonate (LAS). Finally, stability to water hardness, dishwashing test, and detergency performance were evaluated. Expectedly, these products may be used as LAS partners either in heavy-duty powders or in hand dishwashing liquids. Experimental results on Φ-MES of varying carbon number indicate that C₁₆ is the optimal carbon chain length.     

Chromatographic analysis of sorbitan fatty acid esters

A procedure is described for the separation, identification and quantitative estimation of mono-, di- and tri-fatty acid esters of sorbitol and of its anhydrides. Stearic, palmitic and oleic acid esters of sorbitol, 1,4-sorbitan and isosorbide were synthesized in the laboratory. Lipid classes were separated by liquid partition column chromatography and TLC. The individual mono-and di-fatty acid esters and the polyols were analyzed by GLC as trimethylsilyl ethers. Recoveries of known compounds in mixtures were in a range of 92% to 100%. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April 1968.     

Dilatometric investigations of fatty acid methyl esters

Summary The coefficients of expansion and melting dilations were measured for methyl palmitate, methyl stearate, methyl arachidate, methyl behenate, and methyl oleate. The dilatometric curve for the heating cycle of methyl palmitate and methyl stearate in the solid state was composed of a linear section to 49 degrees below the melting point, followed by a curvilinear section to the melting point. The heating and cooling cycle curves for methyl palmitate show the same volume change from −38°C. to 29°C., but the shape of the curves is different. The same relation holds for methyl stearate from −38°C. to 37.5°C. “After-contractions” were found in volume measurements within a few degrees of the melting point of both esters. Equilibrated points were found within 0.5 degrees of the final melting temperature of methyl stearate. A striking similarity exists between curves for variation of the dielectric constant with temperature for long chain linear molecules and the dilatometric data. Presented at the fall meeting, American Oil Chemists' Society, Mnneapolis, Minn., October 11, 1954. Issued as Paper No. 196 on the “Uses of Plant Products” and as N.R.C. No. 3671.     

α-sulfonated fatty acid esters: II. Solution behavior of α-sulfonated fatty acid polyethylene glycol esters

Sodium α-sulfonated, fatty acid polyethylene glycol monoesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n H] and diesters [C _m H_2m+1CH(SO₃Na)COO(C₂H₄O) _n COCH(SO₃Na)C _m H_2m+1], wherem=10–16 andn=1–35, were prepared by esterification of α-sulfonated, fatty acids with polyethylene glycols, followed by neutralization with NaOH. Crude products were purified by reversed-phase column chromatography on an octadecyl-modified silica gel. Characteristic solution behavior of these α-sulfonated fatty acid esters was, examined, and the following features were observed. All monoesters prepared in this work had Krafft points below 0°C and also possessed good calcium stabilities. Critical micelle concentrations of the monoesters increased monotonously, as a rule, with an increase in the number of oxyethylene units. These results suggest that the polyethylene glycol residue of the monoester behaves as a hydrophile. On the other hand, diesters possessed high water solubility, low foamability, and critical micelle concentrations that were lower by a factor of ten compared to those of the monoesters.     

TBP-NO_2对乳酸酯的氧化性能研究

采用磷酸三丁酯(TBP)作为吸收剂吸收NO2,制成新型氧化剂TBP-NO2,并对该氧化剂催化氧化乳酸酯的反应进行了研究,系统讨论了氧化剂用量、反应温度、催化剂用量等因素对反应的影响。研究结果表明:TBP-NO2是一种性能温和的氧化剂,能高效地将乳酸酯氧化为丙酮酸酯,反应具有较高的选择性。氧化反应完成后,TBP可以回收并加以循环使用,从而为NO2废气的治理与利用提供了一条新途径。     

Chlorophyll-sensitized peroxidation of saturated fatty acid esters

Chlorophyll-sensitized peroxidation of methyl laurate and methyl stearate was carried out at 30–40 C under intermittent exposure to light from a 500 w tungsten bulb. Hydroperoxides were isolated by solvent partition, reduced to hydroxy esters and purified by silicic acid column chromatography and preparative thin layer chromatography (TLC). Gas liquid chromatography, TLC, IR spectrophotometry, NMR and mass spectroscopy of the hydroxy esters showed that the oxygen attack was exclusively on the α-methylenic carbon atom. One of 28 papers presented at the Symposium, “Metal-Catalyzed Lipid Oxidation,” ISF-AOCS World Congress, Chicago, September 1970.