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Linoleic acid melting point

Fatty acids have also been converted to difunctional monomers for polyanhydride synthesis by dimerizing the unsaturated erucic or oleic acid to form branched monomers. These monomers are collectively referred to as fatty acid dimers and the polymers are referred to as poly(fatty acid dimer) (PFAD). PFAD (erucic acid dimer) was synthesized by Domb and Maniar (1993) via melt polycondensation and was a liquid at room temperature. Desiring to increase the hydrophobicity of aliphatic polyanhydrides such as PSA without adding aromaticity to the monomers (and thereby increasing the melting point), Teomim and Domb (1999) and Krasko et al. (2002) have synthesized fatty acid terminated PSA. Octanoic, lauric, myristic, stearic, ricinoleic, oleic, linoleic, and lithocholic acid acetate anhydrides were added to the melt polycondensation reactions to obtain the desired terminations. As desired, a dramatic reduction in the erosion rate was obtained (Krasko et al., 2002 Teomim and Domb, 1999). [Pg.178]

Melting Points of Lipids The melting points of a series of 18-carbon fatty acids are stearic acid, 69.6 °C oleic acid, 13.4 °C linoleic acid, - 5 °C and linolenic acid, - 11 °C. (a) What structural aspect of these 18-carbon fatty acids... [Pg.367]

The reaction mechanism for the selective hydrogenation of edible oils is very complex. Figure 14.1 illustrates a reaction scheme for linoleic acid. In this scheme, (n m) is used to represent an oil with n carbon atoms and m double bonds. There are several parallel, consecutive, and side reactions. Oleic acid (cis 18 1) is the desired product when the reaction starts with linolenic (all-cis 18 3) or linoleic acid (cis, cis 18 2). In the hydrogenation of linolenic and linoleic acid, elaidic acid (trans 18 1) is formed in a cisjtrans isomerization reaction. From the viewpoint of dietics, elaidic acid is an undesirable product however, its presence increases the melting point of the product in a desirable way. Stearic acid (18 0) is formed in a consecutive reaction, but direct formation from linoleic acid is also possible. [Pg.229]

A second double bond lowers the melting point further (linoleic acid, mp — 5 °C), and a third double bond lowers it still further (linolenic acid, mp —11 °C). The trans double bonds in eleostearic acid (mp 49 °C) have a smaller effect on the melting point than the cis double bonds of linolenic acid. The geometry of a trans double bond is similar to the zigzag conformation of a saturated acid, so it does not kink the chain as much as a cis double bond. [Pg.1204]

Linoleic Acid occurs as a colorless to pale yellow, oily liquid that is easily oxidized by air. It is an essential fatty acid and the major constituent of many vegetable oils, including cottonseed, soybean, peanut, corn, sunflower seed, safflower, poppy seed, and linseed. Its specific gravity is about 0.901, and its refractive index is about 1.469. It has a boiling point ranging from 225° to 230° and a melting point around -5°. One milliliter dissolves in 10 mL of petroleum ether. It is freely soluble in ether soluble in absolute alcohol and in chloroform and miscible with dimethylformamide, fat solvents, and oils. It is insoluble in water. [Pg.255]

D) Linoleic Acid.—The ester is dissolved in 200 cc. of a 5 per cent alcoholic (Note 21) solution of sodium hydroxide in a 400-cc. beaker and is allowed to saponify overnight at room temperature. The resulting jelly is dissolved in 200 cc. of warm water, and a slow stream of carbon dioxide is introduced, beneath the surface of the liquid, while it is acidified with 50 cc. of dilute sulfuric acid (1 1 by volume). The stream of carbon dioxide is maintained throughout the subsequent operations. The linoleic acid rises to the surface as a clear layer. The water layer is siphoned off the acid is washed once with hot water and then dried over anhydrous sodium sulfate and preserved under carbon dioxide. The yield is 10-12 g. of material having a melting point of —8° to —9° C. (Note 22). [Pg.40]

Table 10.2 lists the structure and melting point of four fatty acids containing 18 carbon atoms. Stearic acid is one of the two most common saturated fatty acids, and oleic and linoleic acids are the most common unsaturated ones. The data show the effect of Z double bonds on the melting point of fatty acids. [Pg.370]

Clarity at or below ambient room temperature is the primary characteristic of a liquid oil. Natural vegetable oils that are liquid at room temperatures in temperate climates, 75 5°F (23.4 3°C), contain high levels of unsaturated fatty acids with low melting points. Fatty acids with one or more double bonds and 18 carbon atoms are the most important unsaturated fatty acids for liquid oils. Oleic (18 1), a monounsaturated fatty acid, is the most widely distributed and most stable Ci8 unsaturated fatty acid. Linoleic (18 2) and linolenic (18 3) are the most widely distributed di- and triunsaturated fatty acids. Both of these polyunsaturated fatty acids are termed essential because they cannot be synthesized by animals, including man, and must be supplied in the diet. Complete exclusion of the essential fatty acids from the diet results in scaly skin, loss of weight, kidney lesions and eventually death. [Pg.224]

The melting points of unsaturated fatty acids are lower than those of saturated fatty acids with the same number of carbons (compare stearic, oleic, linoleic, and linolenic acids in Table 19-1). The more double bonds present, the lower the melting point of the fatty acid. The effect of a double bond in lowering the melting point is a consequence of its presence in nature in the cis geometry instead of trans. Unsaturated fatty acids are liquids at temperatures where saturated fatty acids are solids. [Pg.374]

Saturated FA, such as palmitic and stearic acids, are stable toward oxidation and polymerization. Because they have a high melting point, they add structure to certain products. However, due to this characteristic the appearance of a fried food may be adversely affected (e.g., waxy mouth-feel, dry surface of stored fried food). Monoenoic FA, primarily oleic acid, are considered to be beneficial from a health standpoint. Frying oils rich in such FA do not add to the structure they are stable against oxidation and provide a light taste. Polyenoic FA (PEFA) deteriorate more rapidly that monoenoic FA and the shelf life of products fried in oils rich in these acids is shorter. Oxidation products formed from PEFA vary widely, depending on the structure of the FA and the relative concentration of linoleic and linolenic acids. The percentage of linolenic acid in heated oils should be very low. [Pg.336]


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See also in sourсe #XX -- [ Pg.237 ]

See also in sourсe #XX -- [ Pg.595 ]

See also in sourсe #XX -- [ Pg.368 ]




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