Fatty unsaturated

Reformatski reaction Aldehydes and ketones react with a-bromo- fatty acid esters in the presence of zinc powder to give -hydroxy-esters which may be dehydrated to give a-, 0-unsaturated esters. a-Chloroesters will react if copper powder is used in conjunction with the zinc. 

The organophilic part R can come from a natural fatty acid whose carbon number is around 18 and whose chain contains a number of unsaturated bonds. Dimers of fatty acids (Cgg diacids) have also been used. 

The intermediate m hydrogenation formed by reaction of the unsaturated ester with the hydrogenated surface of the metal catalyst not only can proceed to the saturated fatty acid ester but also can dissociate to the original ester having a cis double bond or to its trans stereoisomer Unlike polyunsaturated vegetable oils which tend to reduce serum cholesterol levels the trans fats produced by partial hydrogenation have cholesterol raising effects similar to those of saturated fats... 

Prostaglandins arise from unsaturated C20 carboxylic acids such as arachidonic acid (see Table 26 1) Mammals cannot biosynthesize arachidonic acid directly They obtain Imoleic acid (Table 26 1) from vegetable oils m their diet and extend the car bon chain of Imoleic acid from 18 to 20 carbons while introducing two more double bonds Lmoleic acid is said to be an essential fatty acid, forming part of the dietary requirement of mammals Animals fed on diets that are deficient m Imoleic acid grow poorly and suffer a number of other disorders some of which are reversed on feed mg them vegetable oils rich m Imoleic acid and other polyunsaturated fatty acids One function of these substances is to provide the raw materials for prostaglandin biosynthesis... 

Residual monomers in the latex are avoided either by effectively reacting the monomers to polymer or by physical or chemical removal. The use of tert-huty peroxypivalate as a second initiator toward the end of the polymeri2ation or the use of mixed initiator systems of K2S20g and tert-huty peroxyben2oate (56) effectively increases final conversion and decreases residual monomer levels. Spray devolatili2ation of hot latex under reduced pressure has been claimed to be effective (56). Residual acrylonitrile also can be reduced by postreaction with a number of agents such as monoamines (57) and dialkylamines (58), ammonium—alkali metal sulfites (59), unsaturated fatty acids or their glycerides (60,61), their aldehydes, esters of olefinic alcohols, cyanuric acid (62,63), andmyrcene (64). 

In the area of moleculady designed hot-melt adhesives, the most widely used resins are the polyamides (qv), formed upon reaction of a diamine and a dimer acid. Dimer acids (qv) are obtained from the Diels-Alder reaction of unsaturated fatty acids. Linoleic acid is an example. Judicious selection of diamine and diacid leads to a wide range of adhesive properties. Typical shear characteristics are in the range of thousands of kilopascals and are dependent upon temperature. Although hot-melt adhesives normally become quite brittle below the glass-transition temperature, these materials can often attain physical properties that approach those of a stmctural adhesive. These properties severely degrade as the material becomes Hquid above the melt temperature. 

Table 9. UOP Sorbex Separation of Saturated and Unsaturated Tall Oil Fatty Acids...

The state of knowledge in the early 1990s of the effects of fat on health lacks clarity and general agreement. There is great support for the thesis that fully saturated fats are associated with problems of atherosclerosis and arterial fatty deposit, but there is evidence that stearates, which are saturates, are only poorly utilized in human digestion. Another body of work has estabUshed a connection between unsaturated fatty acids and a better state of arterial health and lowered fat body attachment to the arterial wall (23) contrary evidence exists that highly unsaturated fats polymerize more readily and thus contribute to arterial plaque formation. 

The unsaturated fatty acids, linoleic [60-33-3] and linolenic [463-40-17, contain two and three double bonds and are considered beneficial components of the diet. The double bond is an essential ingredient for human nutrition when it is in the correct position on the fat molecule. Humans are unable to insert the double bond at the omega-3 and -6 position. Therefore, fatty acids containing double bonds at these positions are essential in the diet, including linoleic and linolenic acids. They are accordingly described as essential fatty acids (EFA) (23). 

Chemical bleaching is never used on oils intended for edible use because it oxidizes unsaturated fatty acids to cause off-flavors. However, it does find wide usage for specialty linseed oil, for the paint industry, and fatty chemicals such as sorbitan esters of fatty acids and sodium stearoyl lactylate. Residual peroxide is destroyed by heating above its decomposition temperature. 

Sohd fats may show drastically different melting behavior. Animal fats such as tallow have fatty acids distributed almost randomly over all positions on the glycerol chain. These fats melt over a fairly broad temperature range. Conversely, cocoa has unsaturated fatty acids predominantly in the 2 position and saturated acids in the 1 and 3 positions. Cocoa butter is a brittle sohd at ambient temperature but melts rapidly just below body temperature. 

Measurement of Unsaturation. The presence of double bonds in a fatty acid side chain can be detected chemically or through use of instmmentation. Iodine value (IV) (74) is a measure of extent of the reaction of iodine with double bonds the higher the IV, the more unsaturated the oil. IV may also be calculated from fatty acid composition. The cis—trans configuration of double bonds may be deterrnined by infrared (59) or nmr spectroscopy. Naturally occurring oils have methylene-intermpted double bonds that do not absorb in the uv however, conjugated dienes maybe deterrnined in an appropriate solvent at 233 nm. 

Fa.ts nd Oils. Eats and oils from rendering animal and fish offal and vegetable oilseeds provide nutritional by-products used as a source of energy, unsaturated fatty acids, and palatabiHty enhancement. Eats influence the texture in finished pet foods. The use and price of the various melting point fats is deterrnined by the type and appearance of the desired finished food appearance. 

The antagonisms that exist between unsaturated fatty acids, and carotene and vitamin E are compHcated and largely undefined. Linoleic acid acts as an antivitamin to i7/-a-tocopherol [59-02-9, 1406-18-9, 10191-41-0] (vitamin E) by reducing availabiHty through direct intestinal destmction. Various Hpoxidases destroy carotenes and vitamin A (73). Dicoumarol [66-76-2] (3,3 -methylenebis(4-hydroxycoumarin)) is a tme antimetaboHte of vitamin K [12001 -79-5] but seems to occur only in clover and related materials that are used primarily as animal feeds (74). 

Epidemiologic studies in Japan indicate an increased risk of stomach cancer owing to consumption of broiled fish and meats (116). In the United States, stomach cancer incidence has steadily declined since the 1940s, whereas consumption of broiled food has increased (108). In addition, the average human intake of PAHs is only 0.002 of that required to produce cancer in half of animals fed. Test results are often contradictory (117) and many components of food, such as vitamin A, unsaturated fatty acids, thiols, nitrites, and even saUva itself, tend to inhibit the mutagenic activity of PAHs (118—120). Therefore, the significance of PAHs in the human diet remains unknown (121,109). 

He/minthosporium (15). The mode of action is considered to be inhibition of the enzyme NADPH-cytochrome C reductase, which results in the generation of free radicals and/or peroxide derivatives of flavin which oxidize adjacent unsaturated fatty acids to dismpt membrane integrity (16) (see Enzyme inhibitors). 

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