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.     

Phospholipid synthesis by chick retinal microsomes: Fatty acid preference and effect of fatty acid binding protein

The acylation of 1-palmitoyl-sn-glycerophosphocholine (1-16∶0-GPC) or 1-palmitoyl-sn-glycerophosphoethanolamine (1-16∶0-GPE) was measured using the microsomal fraction prepared from retinas of 14–15-day-old chick embryos. Rates of incorporation of exogenously supplied fatty acids into diacyl-GPC were generally 5–7 times greater than into diacyl-GPE. Substrate preferences for incorporation into diacyl-GPC and diacyl-GPE were, respectively, 18∶2>18∶3=20∶5>20∶4>18∶1>22∶6=18∶0 and 18∶2>22∶6≽18∶3=18∶0≽20∶4=18∶1>20∶5. The apparent selectivities were not consistent with the reported fatty acid compositions of these lipid classes. The addition of partially purified fatty acid binding protein (FABP) to the reaction had no effect either on overall rates of incorporation or on the substrate preference. When fatty acyl-CoA substrates were used, rates of incorporation of the 18∶0 derivative were much higher than with the fatty acid, while rates with other fatty acyl-CoA were similar to those with the respective fatty acid. Substrate preferences for CoA derivatives incorporated into diacyl-GPC were: 18∶0>20∶4>18∶2≽22∶6, and into diacyl-GPE: 20∶4=22∶6>18∶0>18∶2. Polyunsaturated fatty acyl CoA (PUFA-CoA) were thus favored for incorporation into diacyl-GPE, and to a lesser extent into diacyl-GPC, a result that is consistent with composition data. When purified FABP was added to the reactions, there was an increase in the incorporation of 18∶0-CoA and a decrease or no change in the incorporation of PUFA-CoA. The deacylation/reacylation cycle thus appears to play a role in the modification of phospholipid composition. The data are not consistent, however, with a role for FABP in directing PUFA toward membrane lipid synthesis.     

Alkaline cleavage of hydroxy unsaturated fatty acids. I. Ricinoleic acid and lesquerolic acid

The effects of temperature and media on the fusion of ricinoleic and lesquerolic acid derivatives with concentrated aqueous alkali were examined. Improved yields ofω-hydroxy acids were obtained by use of excess 2-octanol. The effect of excess 2-octanol is discussed in relation to a recently proposed reaction mechanism. A laboratory of the W. Utiliz. Res. Devel. Div., ARS, USDA.     

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.     

New polymer syntheses. Part 7. New unsaturated polyurethanes: synthesis and characterization†

A novel series of polyurethanes was prepared via step-growth solution polymerization, by reaction of arylidene monomers, e g 2,5 bis(4-hydroxybenzylidene)cyclopentanone ( I ), 2,5-divanillylidenecyclopentanone ( II ), 2,6-bis(4-hydroxybenzylidene)cyclohexanone ( III ), 2,6-divanillylidenecyclohexanone ( IV ) or 2,7-bis(4-hydroxybenzylidene)cycloheptanone ( V ) with diisocyanates such as toluylene diisocyanate and methylene bis(4-phenylisocyanate). To characterize these polymers, the corresponding model compounds were prepared from monomers I–V and phenylisocyanate. The polymers were characterized by reduced viscosity measurements, IR spectroscopy, ¹H NMR, solubility and determination of their crystallinity. Characterization of the model compounds was accomplished by elemental analysis, IR and ¹H NMR spectroscopy. The thermal stabilities of the polymers were evaluated by thermogravimetric analysis. The morphology of one of these polymers was examined by scanning electron microscopy. © 1999 Society of Chemical Industry     

Studies in autoxidation Part I. The volatile by-products resulting from the autoxidation of unsaturated fatty acid methyl esters

The by-products produced during the autoxidation of the methyl esters of three unsaturated fatty acids, under the influence of a number of promoters, have been studied. The components of the by-products have been separated and identified using GC-MS methods. Mechanisms are proposed to account for their formation.     

New coupling method without heavy metals for the synthesis of a new class of fatty acid methyl ester oligoglycoside ethers

A new method, using poly-O-acetyl-β-d-glycopyranosylbromide, methyl 9-or methyl 12-hydroxyoctadecanoate and triethylamine as catalyst, is described for the synthesis of a new class of nonionic surfactants. Chemical structures were identified using ¹H and ¹³C nuclear magnetic resonance spectroscopy including two-dimensional techniques and Fourier transforming infrared. Critical micelle concentrations and surface tension profiles of these O-alkyl-β-d-glycosides in water were determined.     

Nonionic surfactants. Regioselective synthesis of fatty acid esters of α- and β-glucopyranose

Lipophilic esters of saccharides belong to the family of nonionic surfactants widely employed in pharmaceutical and cosmetics formulations. A very simple method is presented whereby 6-O-esters of α- and β-glucose can be prepared and isolated. Good results have been obtained in the synthesis of 6-O-oleyl derivatives by simple acylation with appropriate oleyl chloride. The condensing agent bis(2-oxo-3-oxazolidinyl) phosphinic chloride (BOP-Cl) allows the preparations of the same esters with better regioselectivity but with yields strongly dependent on the aliphatic chain length of the carboxylic acids employed.     

Alkaline cleavage of hydroxy unsaturated fatty acids and derivatives. II 10-hydroxydecanoic acid from ricinoleates and 1,10-decanediol from ricmoleyl alcohol

The 10-hydroxydecanoic acid is formed in good yield when raw castor oil or methyl ricinoleate is fused with alkali in the presence of a high-boiling unhindered primary or secondary alcohol at 185-195C bath temperature. When non-reducing solvents or hindered alcohols are used, large amounts of sebacic acid form. Iso-octanol (mixed isomers) is a suitable and potentially economical medium for producing high yields of 10-hydroxydecanoic acid. Cleavage of ricinoleyl alcohol produces 1,10-decanediol. W. Utiliz. Res. Dev. Div., ARS, USDA.     

Enzymatic esterification of glycerol III. Lipase-catalyzed synthesis of regioisomerically pure 1,3-sn-diacylglycerols and 1 (3)-rac-monoacylglycerols derived from unsaturated fatty acids

Lipases that display high regioselectivities and broad substrate tolerance were used as catalysts for the efficient esterification of glycerol under the conditions of irreversible acyl transfer. A variety of unsaturated fatty acids, such as oleic, linoleic, erucic, ricinolic, hydroxystearic and coriolic acid, were used for this purpose in the form of their vinyl esters. Suitable biocatalysts were chosen on the basis of systematic screening experiments regarding their regioselectivities (RE) and substrate tolerances. Distinct differences were found and expressed in numerical RE values as a measure for differences of these biocatalysts as being specific, selective, and nonspecific. Based on these experiments, a variety of molecules were synthesized on a preparative scale (>150 mmol) in good yield (ca.85%) and with high regioisomerical purities (>95% RE).     

Factors which affect the stability of highly unsaturated fatty acids. II. The autoxidation of linoleic and alkali conjugated acid in the presence of metallic naphthenates

Summary The addition of commercial paint driers to unconjugated linoleic acid increased the rate of diene conjugation during autoxidation and greatly lowered the amount of detectable peroxides. On the other hand, the addition of driers to the conjugated isomer lowered the amount of detectable peroxide but mildly promoted destruction of diene conjugation. The hydroperoxide decomposition role of driers is further supported. Metallic naphthenates increased the quantity of diene ketones in both unconjugated and conjugated acid though after a longer period of time in the latter case. The subject matter of this paper has been undertaken in cooperation with the office of Naval Research. The opinions or conclusions contained in this report are those of the authors. They are not to be construed as necessarily reflecting the views or indorsement of the Navy Department. Portion of a thesis presented by A. H. Jackson as partial fulfillment of the requirements for the degree of Master of Science in Chemistry at Kansas State College. Contribution No. 367, Department of Chemistry, Kansas State College.     

Analysis of fatty acid methyl esters with high accuracy and reliability. V. Validation of theoretical relative response factors of unsaturated esters in the flame lonization detector

Because unsaturated fatty acid methyl esters (FAME) are subject to autoxidation, it is virtually impossible to obtain and maintain high purity standards. Accordingly, it is not possible to determine flame ionization detector response factors by the usual technique of analyzing standard mixtures of known composition. In an alternative approach, the response factors of methyl oleate, methyl linoleate, methyl linolenate, methyl arachidonate and methyl 4,7,10,13,16,19-docosahexaenoate relative to methyl stearate were estimated by determining the peak areas before and after quantitative hydrogenation in the presence of an internal standard. The estimates showed excellent agreement in all cases with the theoretical factors predicted by Ackman and Sipos and thus constitute an independent and unambiguous proof that the theoretical factors are highly accurate for all olefinic unsaturated FAME. Whereas it is common practice to determine an empirically derived correction factor for each FAME by analyzing standard mixtures of known composition, the thesis is now proposed that, for both saturated and olefinic unsaturated FAME, the proper approach to accurate analysis requires that peak areas be corrected using the theoretical response factors as the only correction factors. If the correct result cannot be obtained when analyzing a primary standard of saturated FAME, it is an indication of faulty technique or equipment, and the only acceptable resolution of the problem is to locate and correct the fault(s).     

鞍钢七高炉炉体循环冷却水系统不用酸不停产化学除锈技术研究

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