Fatty branched

An essential component of cell membranes are the lipids, lecithins, or phosphatidylcholines (PC). The typical ir-a behavior shown in Fig. XV-6 is similar to that for the simple fatty-acid monolayers (see Fig. IV-16) and has been modeled theoretically [36]. Branched hydrocarbons tails tend to expand the mono-layer [38], but generally the phase behavior is described by a fluid-gel transition at the plateau [39] and a semicrystalline phase at low a. As illustrated in Fig. XV-7, the areas of the dense phase may initially be highly branched, but they anneal to a circular shape on recompression [40]. The theoretical evaluation of these shape transitions is discussed in Section IV-4F. 

Fatty acids derived from animal and vegetable sources generally contain an even number of carbon atoms siace they are biochemically derived by condensation of two carbon units through acetyl or malonyl coenzyme A. However, odd-numbered and branched fatty acid chains are observed ia small concentrations ia natural triglycerides, particularly mminant animal fats through propionyl and methylmalonyl coenzyme respectively. The glycerol backbone is derived by biospeciftc reduction of dihydroxyacetone. 

The basic flow sheet for the flotation-concentration of nonsulfide minerals is essentially the same as that for treating sulfides but the family of reagents used is different. The reagents utilized for nonsulfide mineral concentrations by flotation are usually fatty acids or their salts (RCOOH, RCOOM), sulfonates (RSO M), sulfates (RSO M), where M is usually Na or K, and R represents a linear, branched, or cycHc hydrocarbon chain and amines [R2N(R)3]A where R and R are hydrocarbon chains and A is an anion such as Cl or Br . Collectors for most nonsulfides can be selected on the basis of their isoelectric points. Thus at pH > pH p cationic surfactants are suitable collectors whereas at lower pH values anion-type collectors are selected as illustrated in Figure 10 (28). Figure 13 shows an iron ore flotation flow sheet as a representative of high volume oxide flotation practice. 

Lighter C —Cg a-olefias and Cg branched olefins are converted by the oxo process into fatty acids containing one carbon number greater than the starting a-olefin. These fatty acids are then used to produce alkenylhen enesulfonic acid products which are used ia the United States and ia Europe as perborate bleach activators ia heavy-duty laundry detergents. 

Economic aspects. Fatty acids from tall oil, Branched-chain acids, Trialkylacetic acids. 

Many substituted, ie, branched, fatty acids, particularly methacryUc, 2-ethylhexanoic, and ricinoleic acids, are commercially significant. Several substituted fatty acids exist naturally (Table 5). Fatty acids with a methyl group in the penultimate position are called iso acids, and those with a methyl group in the antepenultimate position are called anteiso acids (1) (see Carboxylic acids, branched-CHAIN acids). However, the term iso is often used in a broader sense to mean branched or mixtures of branched-chain industrial acids. 

D. V. Kinsman, "Branched-Chain Fatty Acids," in R. W. Johnson and E. Frit2, eds.. Fatty A.cids in Industry Marcel Dekker, Inc., New York, 1989,... 

Molecular Interactions. Various polysaccharides readily associate with other substances, including bile acids and cholesterol, proteins, small organic molecules, inorganic salts, and ions. Anionic polysaccharides form salts and chelate complexes with cations some neutral polysaccharides form complexes with inorganic salts and some interactions are stmcture specific. Starch amylose and the linear branches of amylopectin form inclusion complexes with several classes of polar molecules, including fatty acids, glycerides, alcohols, esters, ketones, and iodine/iodide. The absorbed molecule occupies the cavity of the amylose helix, which has the capacity to expand somewhat to accommodate larger molecules. The starch—Hpid complex is important in food systems. Whether similar inclusion complexes can form with any of the dietary fiber components is not known. 

Clay-catalyzed dimerization of unsaturated fatty acids appears to be a carbonium ion reaction, based on the observed double bond isomerization, acid catalysis, chain branching, and hydrogen transfer (8,9,11). 

Molecular distillation occurs where the vapor path is unobstmcted and the condenser is separated from the evaporator by a distance less than the mean-free path of the evaporating molecules (86). This specialized branch of distillation is carried out at extremely low pressures ranging from 13—130 mPa (0.1—1.0 p.m Hg) (see Vacuum technology). Molecular distillation is confined to appHcations where it is necessary to minimize component degradation by distilling at the lowest possible temperatures. Commercial usage includes the distillation of vitamins (qv) and fatty acid dimers (see Dimeracids). 

Properties are furthermore determined by the nature of the organic acid, the type of metal and its concentration, the presence of solvent and additives, and the method of manufacture. Higher melting points are characteristics of soaps made of high molecular-weight, straight-chain, saturated fatty acids. Branched-chain unsaturated fatty acids form soaps with lower melting points. Table 1 Hsts the properties of some soHd metal soaps. 

Paint and varnish manufacturing Resin manufacturing closed reaction vessel Varnish cooldng-open or closed vessels Solvent thinning Acrolein, other aldehydes and fatty acids (odors), phthalic anhydride (sublimed) Ketones, fatty acids, formic acids, acetic acid, glycerine, acrolein, other aldehydes, phenols and terpenes from tall oils, hydrogen sulfide, alkyl sulfide, butyl mercaptan, and thiofen (odors) Olefins, branched-chain aromatics and ketones (odors), solvents Exhaust systems with scrubbers and fume burners Exhaust system with scrubbers and fume burners close-fitting hoods required for open kettles Exhaust system with fume burners... 

In addition to unsaturated fatty acids, several other modified fatty acids are found in nature. Microorganisms, for example, often contain branched-chain fatty acids, such as tuberculostearic acid (Figure 8.2). When these fatty acids are incorporated in membranes, the methyl group constitutes a local structural perturbation in a manner similar to the double bonds in unsaturated fatty acids (see Chapter 9). Some bacteria also synthesize fatty acids containing cyclic structures such as cyclopropane, cyclopropene, and even cyclopentane rings. 

Although /3-oxidation is universally important, there are some instances in which it cannot operate effectively. For example, branched-chain fatty acids with alkyl branches at odd-numbered carbons are not effective substrates for /3-oxidation. For such species, a-oxidation is a useful alternative. Consider phy-tol, a breakdown product of chlorophyll that occurs in the fat of ruminant animals such as sheep and cows and also in dairy products. Ruminants oxidize phytol to phytanic acid, and digestion of phytanic acid in dairy products is thus an important dietary consideration for humans. The methyl group at C-3 will block /3-oxidation, but, as shown in Figure 24.26, phytanic acid a-hydroxylase places an —OFI group at the a-carbon, and phytanic acid a-oxidase decar-boxylates it to yield pristanie add. The CoA ester of this metabolite can undergo /3-oxidation in the normal manner. The terminal product, isobutyryl-CoA, can be sent into the TCA cycle by conversion to succinyl-CoA. 

FIGURE 24.26 Branched-chain fatty acids are oxidized by o -oxidation, as shown for phytanic acid. The product of the phytanic acid oxidase, pristanic acid, is a suitable substrate for normal /3-oxidation. Isobutyryl-CoA and propionyl-CoA can both be converted to suc-cinyl-CoA, which can enter the TCA cycle. 

Higher molecular primary unbranched or low-branched alcohols are used not only for the synthesis of nonionic but also of anionic surfactants, like fatty alcohol sulfates or ether sulfates. These alcohols are produced by catalytic high-pressure hydrogenation of the methyl esters of fatty acids, obtained by a transesterification reaction of fats or fatty oils with methanol or by different procedures, like hydroformylation or the Alfol process, starting from petroleum chemical raw materials. 

The industrial production of fatty acids on the basis of petrochemical raw materials is of secondary importance in comparison with their preparation from natural materials. Only short-chain or branched or odd-numbered carboxylic acids, for which natural sources don t exist, have to be prepared by different synthetic methods. 

R is mostly derived from natural fatty alcohols and is generally between C6H13 and C18H37. Sometimes R is partly unsaturated. On behalf of special applications R can also be derived from branched fatty alcohols, such as oxoalcohols or Guerbet alcohols. 

These are two chemically different groups of products which have distinct application fields. Both product groups are obtained by reacting maleic acid anhydride (MA) with hydroxyl group(s)-carrying molecules, followed by sulfation of the intermediate product, an ester. Whereas the diester types are mainly made from a few different branched and unbranched alcohols, the monoester are derived from a wide variety of raw materials fatty alcohols, fatty acid alkanolamides, ethoxylated fatty alcohols, fatty acid alkanolamides, their etho-xylates, and others. All these raw materials—with the exception of the branched chains—may be obtained from natural renewable resources. 

As far as dialkyl sulfosuccinates are concerned, there are minor variation possibilities known from the market products. Most of the substances available are dialkyl sulfosuccinates. The variation is limited to the fatty chain. Either linear, branched, or cyclic aliphatic groups are used. No ethoxylated sulfosuccinate diesters could be recognized. 

A number of amide- and ester-linked fatty acids and (/ )-3-hydroxy acids are components of the lipid A part in the LPS from Gram-negative bacteria. The acids have been tabulatedand the chemistry of lipid A summarized. The most common acids in lipid A from Enterobacteriaceae are the saturated 12 0,14 0, and 16 0, and the (/ )-3-hydroxy-14 0, The last is linked to N-2 and 0-3 of the 2-amino-2-deoxy-D-glucopyranosyl residues, and the others are ester-linked to the hydroxy acid, as in the lipid A (44) of Salmonella minnesota. Other linear and branched fatty acids, unsaturated acids, S)-2- and (/ )-3-hydroxy acids, and 3-oxotetradecanoic acid are components of lipid A from certain different species. In the lipid A from Rhizobium trifolii, 2,7-dihydroxyoctanoic acid is linked as amide to a 2-amino-2-deoxy-D-gl ucopy ranosy 1 residue. ... 

Saturated fatty acids may be envisaged as based on acetic acid (CId3—COOH) as the first member of the series in which —CHj— is progressively added between the terminal CHj— and —COOH groups. Examples are shown in Table 14-1. Other higher members of the series are known to occur, particularly in waxes. A few branched-chain fatty acids have also been Isolated from both plant and animal sources. 

The catabolism of leucine, valine, and isoleucine presents many analogies to fatty acid catabolism. Metabolic disorders of branched-chain amino acid catabolism include hypervalinemia, maple syrup urine disease, intermittent branched-chain ketonuria, isovaleric acidemia, and methylmalonic aciduria. 

Exposures of 10 weeks (5 days/week) to 2,500 mg/kg/day trichloroethylene in com oil by gavage resulted in altered myelin thickness in the rat mental nerve, a branch of the trigeminal nerve (Barret et al. 1991). Effects of similar exposures on the rat trigeminal nerve included decreased fiber diameter and altered fatty acid composition in total lipid extracts, indicative of demyelination (Barret et al. 1992). Stronger effects were seen with the trichloroethylene decomposition product dichloroacetylene. 

Suzuki T, K Tanaka, I Matsubara, S Kinoshita (1969) Trehalose lipid and alpha-branched-beta-hydroxy fatty acid formed by bacteria grown on -alkanes. Agric Biol Chem 33 1619-1627. 

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