Fatty acids saturated, separation from unsaturated

What is important though is that the double bonds are separated by one and only one single bond. Remember the unsaturated fatty acid, linoleic acid, that you met in Chapter 3 Another fatty acid with even more unsaturation is arachidonic acid. None of the four double bonds in this structure are conjugated since in between any two double bonds there is an sp3 carbon. This means there is no p orbital available to overlap with the ones from the double bonds. The saturated carbon atoms insulate the double bonds from each other. 

The separation of long-chain saturated fatty acids (C16-C18) from the corresponding unsaturated fatty acids by distillation is not practical because of the proximity of their boiling points. However, both the melting points and the solubility (in organic solvents) of these two types of fatty acids are vastly different.20 These properties are used to advantage for separating mixtures of saturated and unsaturated fatty acids into fractions that are rich in either saturated (stearin) or unsaturated (olein) components.19a,b... 

Laurie acid is a fatty carboxylic acid isolated from vegetable and animal fats or oils. For example, coconut oil and palm kernel oil both contain high proportions of lauric acid. Isolation from natural fats and oils involves hydrolysis, separation of the fatty acids, hydrogenation to convert unsaturated fatty acids to saturated acids, and finally distillation of the specific fatty acid of interest. 

On hydrolysis, fi oils yield a mixture of fatty acids derived mainly from mixed glycerides. Separation of these fatty acids based on molecular wei t or degree of unsaturation is oonoplicated by several factors. First, the relatively small differences in their molecular wei ts make it difficult to separate them by conventional means, particularly v en saturated and xmsaturated fatty acids of the same chain length are to be sqparated. Second, polyunsaturated corpouncls are readily susceptible to polymerization, degradation and/or oxidation, even at moderately elevated tenperatures. 

Natural Fatty Acids. Obtained primarily from the hydrolysis of triglycerides such as animal and vegetable fats and oils, the most useful members of the group have from 12 to 18 carbon atoms. The most commonly employed members of the family have hydrocarbon chains that are fully saturated, although some unsaturated examples are employed (especially oleic acid). Because most vegetable oils contain high proportions of unsaturated fatty adds, they usually require extensive processing in order to separate the useful... 

Simulated moving-bed (SMB) processes have been widely nsed for difficult, liquid-phase separations (Ruthven, 1984 Humphrey and Keller, 1997 Juza et al 2000). Sorbex is the generic name used by UOP for these processes. The most important application is the separation of the xylene isomers, named the Parex process. Other commercialized SMB separations include n-paraffins/isoparaffins (Molex), olefins/paraffins (Olex), fructose/glucose (Sarex), and chiral SMB separations (Juza et al., 2000). A host of other separations have been demonstrated (Humphrey and Keller, 1997), although the commercial status of these applications is unknown. These demonsffated separations include separation of hydroxyparaf-finic dicarboxylic acids from olefinic dicarboxylic acids removal of thiophene, pyridine, and phenol from naphtha separation of unsaturated fatty acid methyl esters from saturated fatty acid methyl esters and separation of saturated fatty acids from unsaturated fatty acid (Humphrey and Keller, 1997). 

There are essentially four steps or unit operations in the manufacture of fatty acids from natural fats and oils (/) batch alkaline hydrolysis or continuous high pressure hydrolysis (2) separation of the fatty acids usually by a continuous solvent crystallisation process or by the hydrophilisation process (J) hydrogenation, which converts unsaturated fatty acids to saturated fatty acids and (4) distillation, which separates components by their boiling points or vapor pressures. A good review of the production of fatty acids has been given (1). 

The yolk is separated from the white by the vitelline membrane, and is made up of layers that can be seen upon careful examination. Egg yolk is a complex mixture of water, Hpids, and proteias. Lipid components iaclude glycerides, 66.2% phosphoUpids, 29.6% and cholesterol [57-88-5] 4.2%. The phosphohpids consist of 73% lecithin [8002 3-5] 15% cephahn [3681-36-7], and 12% other phosphohpids. Of the fatty acids, 33% are saturated and 67% unsaturated, including 42% oleic acid [112-80-1] and 7% linoleic acid [60-33-3]. Fatty acids can be changed by modifying fatty acids ia the laying feed (see... 

Gas chromatography (GC or, less commonly, GLC) is the most widely used separation technique for volatile samples. The resolution is sufficient to routinely separate components, such as homologous series, saturated from unsaturated fatty acids, terpenoids, triacylglycerols, etc. The use of a mass spectrometer to identify the separated components (GC-MS) is discussed in Section 8.4. 

Here, we review two organic acid separations the first being citric acid from fermentation broth and the second separates saturated from unsaturated free fatty acids. 

Prepare a table listing the retention time for each standard FAME. Use this table to identify the fatty acids present in each triacylglycerol you analyzed. Alternatively, plot the log of the retention time against the chain length of each saturated FAME (see Figure E6.5). Unknown saturated fatty acids can be identified from experimental retention times using this plot. Unsaturated fatty acids cannot be identified from the plot of saturated FAMEs. A separate plot of log retention time vs. the chain length must be prepared for each level of saturation (saturated, monounsaturation, diunsaturation, etc.). 

Figure D1.6.3 TLC-FID separation of a range of standard lipids. The mobile phase was 91 6 3 1 (v/v/v/v) hexane/ethyl acetate/diethyl ether/formic acid. Time refers to scanning time of the Chromarod. Abbreviations CE, cholesterol ester CHO, cholesterol DG, 1,2-diglyceride 1,3-DG, 1,3-diglyceride FFAU, highly unsaturated free fatty acid FFAS, less unsaturated free fatty acid MG, 1-monoglyceride PL, phosphatidylcholine TGU, highly unsaturated triglyceride TGS, saturated triglyceride. Tripalmitin and palmitic acid were used to complement trilinolenin and linolenic acid. Reproduced from Ackman and Heras (1997) with permission from AOCS Press.

Fig. 29 Separation of triacylglycerols from sunflower seed oil by HPLC with a silver ion column and mass detection. For conditions see text. S = saturated fatty acid M = monounsaturated fatty acid D = di-unsaturated fatty acid.

The separation of individual fatty acid components from whole fatty acid distillates is achieved by fractional distillation.l8a,b However, fractional distillation cannot efficiently separate C,6-C 8 saturated from the corresponding unsaturated fatty acids. In such cases, the melting points vary considerably with the degree of unsaturation and this property is used for their separation via a number of industrial processes.I9a,b... 

Fatty acids may also be enriched by the use of various absorption media. Molecular sieves can separate saturated fatty acids from unsaturated fatty acids dissolved in acetone (110). Oleic acid and linoleic acid dissolved in blends of solvents, including acetonitrile, tetrahydrofuran, water, and formamide, may be separated using cross-linked polystyrene polymers such as Amberlite XAD-2 or XAD. ... 

The first documented fatty acid separation was reported by Guesserow (2). Separation of linear saturated fatty acids from linear unsaturated fatty acids by first preparing the lead salt derivative, dissolving the mixed salts in diethyl ether or ethyl alcohol, and then separating the less soluble saturated acids from the more soluble unsaturated acids has been reported. This was a very efficient method and involved large amounts of solvent and pre-preparation of fatty acid salts that made this process difficult to adopt in commercial scale (3). The classic commercial process of... 

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