Methyl oleate, hydrogenation

In 1977, Kellogg and Fridovich [28] showed that superoxide produced by the XO-acetaldehyde system initiated the oxidation of liposomes and hemolysis of erythrocytes. Lipid peroxidation was inhibited by SOD and catalase but not the hydroxyl radical scavenger mannitol. Gutteridge et al. [29] showed that the superoxide-generating system (aldehyde-XO) oxidized lipid micelles and decomposed deoxyribose. Superoxide and iron ions are apparently involved in the NADPH-dependent lipid peroxidation in human placental mitochondria [30], Ohyashiki and Nunomura [31] have found that the ferric ion-dependent lipid peroxidation of phospholipid liposomes was enhanced under acidic conditions (from pH 7.4 to 5.5). This reaction was inhibited by SOD, catalase, and hydroxyl radical scavengers. Ohyashiki and Nunomura suggested that superoxide, hydrogen peroxide, and hydroxyl radicals participate in the initiation of liposome oxidation. It has also been shown [32] that SOD inhibited the chain oxidation of methyl linoleate (but not methyl oleate) in phosphate buffer. 

The hydrogenation is usually limited to nonpolar alkenes (terminal and internal cyclic and acyclic alkenes), even though Ti systems have been used to hydrogenate alkenes containing ether and ester functionalities such as vinyl ethers or methyl oleate [42, 45, 59, 62]. 

Reduction of ozonides is very useful, especially when aldehydes are the desired products. Ozonides are easily hydrogenolyzed over palladium [670], or reduced by zinc in acetic acid [671], usually in good yields. Ozonolysis of methyl oleate followed by hydrogenation over 10% palladium on charcoal... 

Conclusive evidence for the participation of 7r-allylic intermediates in double bond migration has been obtained from a study of the nickel-catalysed hydrogenation of the isomeric olefinic esters methyl oleate and methyl elaidate using tritium as a tracer [147]. It was also concluded that in this system cis—trans isomerisation occurred by an addition—abstraction mechanism. 

Mecking showed an efficient way to produce a,G>diesters from fatty acid esters yielding excellent monomers for semicrystalline polyesters [63], Some part of the diesters was hydrogenated to diols and was transesterified with the diesters from the hydroesterification of methyl oleate into long-chain polyesters (Scheme 24). The properties of this thermomorphic polymer are related to those of polyethylene. 

Albright, L. and Wisniak, J., J. Amer. Oil Chem. Soc. 39, 14, 1962. Selectivity and Isomerization during Partial hydrogenation of cottonsead oil and methyl oleate Effect of operating variables. ... 

The latter observations with methyl oleate, together with thermodynamic considerations and EPR evidence for free radical intermediates, suggest an alternative explanation for the dramatic increase in oxidation rates once hydroperoxides accumulate, namely that bimolecular decomposition may be specific to allylic hydroperoxides and proceed via LOO radical-induced decomposition rather than by dissociation of hydrogen-bonded dimers (280). Reaction sequence 63 is analogous to Reactions 49 and 50a, where one slowly reacting radical reacts with a... 

To illustrate the principles of slurry operation, we shall consider the hydrogenation of methyl linoleate, L, to form methyl oleate, O ... 

Hydrogen is absorbed in liquid methyl linoleate, diffuses to the external surfaee of the eatalyst pellet, and then diffuses into the catalyst pellet, where it reacts with methyl linoleate, 1 to form methyl oleate, O. Methyl oleate then diffuses out of the pellet into the bulk liquid. 

P12-19 The following table was obtained from the data taken in a slurry reactor for the hydrogenation of methyl linoleate to form methyl oleate. 

P12-20b The catalytic hydrogenation of methyl linoleate to methyl oleate was carried out in a laboratory-scale slurry reactor in which hydrogen gas was bubbled up through the liquid containing spherical catalyst pellets. The pellet density is 2 g/cm. The following experiments were carried out at 25°C ... 

Similar oxidants are used for epoxidation of esters of unsaturated carboxylic acids. Methyl oleate is oxidized with peroxybenzoic acid [295] or peroxylauric acid [174] to methyl 9,10-epoxystearate acid in respective yields of 67 and 76%. Alkaline 50% hydrogen peroxide in methanolic solution transforms diethyl ethylidenemalonate at pH 8.5-9.0 and at 35-40 C over a period of 1 h into ethyl 2-ethoxycarbonyl-2,3-epoxybutyrate in 82% yield [145], A somewhat exotic oxidizing agent, dimethyldioxirane, converts ethyl tra/u-cinnamate into ethyl 2,3-epoxyhydrocinnamate in 63% isolated yield [210]. 

To elucidate the mechanism of homogeneous hydrogenation catalyzed by Fe(CO)s, kinetic studies were carried out with mixtures of unsaturated fatty esters containing a radioactive label. A C-labeled methyl octadecadienoate-Fe(CO)3 complex was prepared to serve as a catalytic intermediate. Hydrogenation of methyl oleate (m-9-octa-decenoate) and palmitoleate (cis-9-hexadecenoate) and of their mixtures with methyl linoleate was also studied to determine the selectivity of this system, the function of the diene-Fe(CO)3 complex, and the mechanism of homogeneous isomerization. Mixtures of reaction intermediates with a label helped achieve unique simulation of the kinetic data with an analog computer. 

We found previously (10) that in a natural mixture of mono-, di-, and triunsaturated fatty esters the hydrogenation of monoenes with Fe(CO)s was minor. Therefore, competitive hydrogenation studies were carried out with an equal mixture of methyl oleate and linoleate. Diene hydrogenation in such a mixture was indeed dominant (Figure 2). At O.IM initial concentration of Fe(CO)s the formation of stearate was a minor reaction the diene-Fe(CO)3 complex reached a maximum of 4% and remained constant. On the other hand, at 0.5M Fe(CO)5, stearate formation became a more important reaction diene-Fe(CO)3 reached a maximum of 7% and decreased during the course of hydrogenation. Free conjugated dienes were minor products. 

Figure 1. Rate curves for hydrogenation of methyl oleate. Run i, O.iM Fe(CO)s...

The ready hydrogenation and isomerization of methyl oleate and palmitoleate with Fe(CO)s confirm the results of Ogata and Misono (18) with monounsaturated aliphatic compounds. In the isomerization of monoolefins Manuel (15) suggested the occurrence of equilibria involving either 7r-olefin HFe(CO)3 and a-alkyl Fe(CO)3 complexes, or TT-olefin Fe(CO)3 and 7r-allyl HFe(CO)3 complexes. The formation of olefin-iron tetracarbonyl complexes has been reported (19). The reaction of butadiene and Fe2(CO)9 has been observed to lead to the formation of butadiene-Fe(CO)4 and butadiene-[Fe(CO)4]2 complexes in which one or both double bonds are pi-bonded to the iron (16). A mechanism involving both monoene-Fe(CO)4 (I) and allyl-HFe(CO)3 complexes (II) is postulated for the isomerization of methyl oleate (Scheme II) and for its homogeneous hydrogenation. 

The Fe(CO)4 intermediates of types III and VIII in Scheme IV explain the direct reduction paths evidenced in the hydrogenation of mono- and diunsaturated fatty esters. Competition between monoene and diene hydrogenation can be related to the stability of the Fe(CO)3-and Fe(CO)4-complexes. At a low concentration of Fe(CO)5, the formation of Fe(CO)a complexes is favored because they are more stable. At a high concentration of Fe(CO)s, formation of mono- and di-Fe(CO)4 complexes becomes important, and selectivity for diene hydrogenation is decreased. Although the occurrence of olefin-Fe(CO)4 complexes has precedence in the literature (i9), no such species has yet been identified with either methyl oleate or linoleate. 

The addition of deuterium to methyl oleate catalyzed by Adams platinum leads to methyl stearates in which up to all but six of the thirty-six hydrogen atoms have been exchanged. Related compounds were also examined (59). 

Figure 7. Methyl esters of unsaturated fatty acids as resolved on the 25%-cyanopropyl-25%-phenyl methyl siloxane DB-225. Split Injection to a 30m x 0.25mm column coated with a 0.25 m bonded film, hydrogen carrier at 46cm/sec, isothermal at 200 °C. Components 1, 14 1 methyl myristoleate 2, 16 1 trans methyl palmite-laidate 3, 16 1 cis methyl palmitoleate 4, 18 1 trans methyl elaidate 5, 18 1 cis methyl oleate 6, 18 2 trans methyl linolea-laidate 7, 18 2 cis methyl linoleate 8, 18 3 methyl linoleate ...

Hydrogenation was carried out in n-hexane solution, which approximates the non-interactive environment of the gas phase. Ahyd//is relative to 125.1 kcal mol 1, (exothermic) for methyl oleate, which was taken as the standard value. 

Y. Pouilloux, A. Piccirilli and J. Barrault, "Selective hydrogenation into oleyl alcohol of methyl oleate in the presence of Ru-Sn/ALOi catalysts" J. Mot. Catal A Chemical, 108,161 (1996). 

Fig. 4.3. (A) Analytical catalytic reactor with bypass. 1 = Catalyst 2 = glass-wool 3 = stainless-steel capillary. (B) Chromatograms of methyl esters of Cj, acids after hydrogenation using the analytical catalytic reactor with bypass. Peaks 1 = methyl stearate 2 = methyl oleate 3 = methyl linoleate 4 = methyl linolenate. Reprinted with permission from ref. 79.

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