Isomerization methyl oleate

A similar reaction occurs with fatty acids (such as stearic acid) or methyl stearate, which undergo isomerization, cracking, dimerization, and oligomerization reactions. This has been used to convert solid stearic acid into the more valuable liquid isostearic acid [102] (Scheme 5.1-70). The isomerization and dimerization of oleic acid and methyl oleate have also been found to occur in chloroaluminate(III) ionic liquids [103]. 

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. 

The production of a,m-diesters from fatty esters can be realized via their SM as already explained, but it can also be performed by CM with methyl acrylate. The bulk CM of several unsaturated fatty acid methyl esters containing double bonds in different positions with methyl acrylate was studied by Rybak and Meier (Scheme 6) [43], C4 and C5 displayed very good activities with high conversions and CM selectivities. Among them, C5 showed the best performance for both methyl oleate (97% conversion, 92% selectivity, with 0.2 mol%) and methyl 10-undecenoate (99% conversion, 99% selectivity, with 0.1 mol%). The same conditions were successfully applied to methyl erucate and methyl petroselinate. The reaction conditions were further optimized, also considering the effect of 1,4-benzoquinone as additive for the reduction of double-bond isomerization [39], The CM of methyl 10-undecenoate and methyl acrylate worked with full conversions and high selectivity if five- to tenfold excess of methyl acrylate is used. Furthermore, using a 1 1 ratio between both reactants led, after optimization of the reaction... 

In the case of rhodium as a catalyst metal for the hydroformylation of methyl oleate, lower pressure and lower temperature have to be compared to cobalt catalysis [20, 21], The use of rhodium is also advantageous because of the lower isomerization. Frankel showed that with a rhodium triphenylphosphine catalyst, hydroformylation occurs only on the ninth and tenth carbon atoms of the methyl oleate [22]. 

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. ... 

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. 

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 first investigations concerning the hydroformylation of fatty compounds were accomplished by Ucciani and co-workers with cobalt catalysts such as cobalt bislaurate and dicobalt octacarbonyl [29]. Later, Frankel and co-workers found that the cobalt-catalyzed hydroformylation of methyl oleate also leads to the corresponding fatty alcohols [30]. In recent investigations on the hydroformylation of fatty compounds, the preferred catalyst is based on rhodium. For instance, the hydroformylation of methyl oleate catalyzed by [Rh(acac)(CO)2]/biphephos yields an isomeric mixture of formylstearic add methyl esters [31]. 

A particularly ambitious synthesis is isomerizing hydroformylation (Equation 3.1). In this reaction, first the internal double bond of the methyl oleate isomerizes to the terminal position, which is then hydroformylated to the co-aldehyde [32],... 

Stereochemical studies based on C-nuclear magnetic resonance spectroscopy ( C-NMR) showed the presence of eight cis and trans allylic hydroperoxides (Table 2.1). To determine the isomeric distribution of allylic hydroxyooctadecenoate derivatives, cis and trans fractions were separated by silver nitrate-thin layer chromatography (TLC), a procedure that separates according to the number, position and geometry of double bonds, and they were hydrogenated prior to GC-MS analyses of the TMS ether derivatives. More recently, the six major hydroperoxide isomers of methyl oleate were partially separated by silica HPLC, and identified by chemical-ionization mass spectrometry and IH NMR (Table 2.1). These hydroperoxide isomers were better separated as the hydroxy octadecenoate derivatives by the same silica HPLC method and re-analysed by GC-MS. 

J. C. Bailar, Jr., and Hiroshi Itatani, Homogeneous Catalysis in the Reactions of Olefinic Substances. VI. Selective Hydrogenation of Methyl Linoleate and Isomerization of Methyl Oleate by Homogeneous Catalysis with Platinum Complexes Containing Triphenylphosphine, Arsine or Stibine, J. Am. Chem. Soc. 89 1592 (1967). 

Scheme 5.21 Isomerization-hydroformylation of methyl oleate with different rhodium phosphite catalysts.

With methyl oleate, 53% yield of the terminal alcohol was observed. With unmodified internal olefins (2-decene, 2-tridecene, 4-octene), even higher regioselectivities in favor of the terminal alcohol could be achieved l/b up to 12 1). Proof was given that both rhodium and ruthenium complexes catalyze the isomerization-hydroformylation-hydrogenation reaction in a cooperative manner. 

Scheme 6.81 Non-isomerizing and isomerizing hydroformylation of methyl oleate.

In comparison to methyl oleate, somewhat higher yields of monoformyl product were observed in the hydroformylation of ethyl linoleate (Scheme 6.83) [26]. Under the same conditions, besides isomeric aldehydes, ethyl oleate and ethyl stearate were formed. Higher syngas pressure reduced the degree of hydrogenation. 

The mechanism for homogeneous hydrogenation of methyl linoleate by Fe(CO)s based on kinetic evidences and radioactive tracers involves monoene- and diene-Fe(CO)4 and diene-Fe(CO)3 complexes as important intermediates. Contrary to our previous postulate (7) the free conjugated diene is only a minor intermediate. Confirmatory evidence is needed for the occurrence of oleate- and linoleate-Fe(CO)4 complexes during hydrogenation and isomerization with Fe(CO)r>. Also, the species of iron carbonyl hydrides formed during hydrogenation should be elucidated. 

Another example of organic synthesis via cross-metathesis is the synthesis of biologically active compounds such as insect pheromones. Use of such pheromones offers an effective and selective pest control method. Thus, cross-metathesis of ethyl oleate with 5-decene results in a cis-trans mixture of ethyl 9-tetradecenoate, an insect pheromone precursor [15]. Cross-metathesis of methyl d.y-5-eicosenoate (obtained from meadowfoam oil) with excess 5-decene gives methyl tm 5-decenoate, which can be transformed into a 83 17 mixture of trani -5-decenylacetate and tran.y-5-decenol (in total 90% trans), the sex pheromone of the Peach Twig Borer moth, a major pest in Northern Hemisphere fruit orchards. The isomeric mixture was active in mating disruption [16]. Other examples of organic synthesis via cross-metathesis are summarised elsewhere [17 18]. 

In a number of other studies, GC-MS of DMOX derivatives has been utilized to determine the CLA isomer distribution from a variety of sources. The structures of pure isomers of 9c,llt-18 2 and 10f,12c-18 2, isolated by crystallization of a CLA mixture prepared by alkali-isomerization of linoleate, were confirmed (67). The presence of 9c,llt-18 2 was established in chocolate (49). In conjunction with GC-FTIR, all possible geometrical isomers of 9,11-18 2 (c,i > t,t > c,c and t,c) were detected in human adipose tissue (10). In dehydrated castor oil, although the 9,11 isomers (c/i, c,c and t,t) appeared to be the most abundant, 7,9- and 8,10-18 2 (c/t and but not c,c) were also detected with the aid of SPA (46). The presence of It, 9c-18 2 (as well as lower levels of 7c,9c-, lt,9t- and possibly 7c,9f-18 2) was confirmed in cow s milk, cheese, beef, and human milk and adipose tissue (9). Together with silver-ion HPLC, the isomer distribution in different tissues of pigs fed commercial CLA was determined (2). The CLA content of lactic acid bacteria (44), and the nature of the CLA isomers formed as a result of add-catalyzed methylation of allylic hydroxy oleates (secondary hpid autoxidation products) (47) were also established. 

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