Glycerides isomerization

S (2)-hydroxy-3-butenenitrile from acrolein and HCN trans hydrocyanation using, for instance, acetone cyanohydrin Hydrolysis of nitriles to amides, e.g. acrylonitrile to acrylamide Isomerization of glucose to fructose Esterifications and transesterifications Interesterify positions 1 and 3 of natural glycerides Oxidation of glucose to gluconic acid, glycolic acid to glyoxalic acid... 

Organic carboxylic acids are commonly found in foods, in the adipate process stream, and as pollutants. Fatty acids are the lipophilic portion of glycerides and a major component of the cell membrane. Phenols are widely used in polymers, as wood preservatives, and as disinfectants. Chloro-phenols such as 4-chlorophenol, two isomeric dichlorophenols, 2,4,6-tri-chlorophenol, three isomeric tetrachlorophenols, and pentachlorophenol were separated on a Dowex (The Dow Chemical Co. Midland, MI) 2-X8 anion exchange resin using an acetic acid-methanol gradient.138... 

Butyric acid is a carboxylic acid also classified as a fatty acid. It exists in two isomeric forms as shown previously, but this entry focuses on n-butyric acid or butanoic acid. It is a colorless, viscous, rancid-smelling liquid that is present as esters in animal fats and plant oils. Butyric acid exists as a glyceride in butter, with a concentration of about 4% dairy and egg products are a primary source of butyric acid. When butter or other food products go rancid, free butyric acid is liberated by hydrolysis, producing the rancid smell. It also occurs in animal fat and plant oils. Butyric acid gets its name from the Latin butyrum, or butter. It was discovered by Adolf Lieben (1836—1914) and Antonio Rossi in 1869. 

Table 4.3 illustrates the triglyceride types and isomeric forms of some natural fats. GS3 in the table refers to a fully saturated glyceride and GS2U refers to a glyceride composed of two saturated acids and one unsaturated acid. Distinguishing between the 1, 3, and 2 positions permits identification of the SUS and SSU isomers of GS2U and the USU and UUS isomers of GSU2. 

Another question is whether it matters how the fatty acids are grouped together in TG that have the same fatty acid composition at each stereospecific position, e.g., a physical or interesterified mixture (by mole) of a 50% trisaturated and 50% triunsaturated mixture. For glycerides in general, it can be asked whether TG have the same effects as DG and MG and whether the isomeric structure of the partial glycerides (sw-l,2-DG, sn-l,3-DG or 5 -2,3-DG and 5M-1-MG, 5 -2-MG or sn-3-MG) matters. Finally, it can be asked whether fatty acids fed as TG have the same effects as the same fatty acids fed as phospholipids (PL). 

Allenic acids, containing the —CH=C=CH— system, occur only rarely in lipids but the known examples are of interest because the glycerides are optically active by virtue of the allene function. Allenic acids are isomeric with acetylenic compounds and each can be rearranged to the other. 

Attempts have been made to modify natural glyceride oils to improve their properties as paint oils by isomerization and by segregation processes. 

Thermal oxidation of unsaturated fats is accompanied by considerable isomerization of double bonds, leading to products containing trans double bonds and conjugated double bond systems. Non-volatile decomposition products are formed by thermal oxidation, hydrolysis and cyclization. A large number of hydroxy, alkoxy-substituted, epoxy and keto compounds are produced by oxidation, free fatty acids and mono- and diacylglycerols by hydrolysis, and cyclic monomers by cyclization of polyunsaturated fatty acids in heated fats. Aldehydo glycerides (also referred to as core aldehydes ) and keto glycerides... 

Considerable difficulties are encountered in subfractionation of glycerides. Partial glycerides (mono- and diglycerides) may isomerize on silicic acid and florisil (Mattson and Volpenheim 1962). Triglycerides are more stable but comprise numerous isomers, the total separation of which has not been achieved. 

Free fatty acids occur only in small amounts in biological materials. They can be recovered from ether or petroleum ether extracts by extraction with diluted aqueous or alcoholic alkaline solutions as the corresponding alkaline salts and reconverted to free acids by treatment with acids. The use of diluted alkaline solutions prevents hydrolytic cleavage of glycerides and glycerophospholipids. Free fatty acids may also be isolated by adsorption to basic ion exchange resins (Carlson and Wadstrom 1958, Hornstein et al. 1960). Because of a tendency of polyunsaturated fatty acids to isomerization Biegler et al. (1960) recommend the use of weak basic adsorbents. After isolation free fatty acids are assayed by titration. 

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