Branched chains acids

Branched-chain acids contain at least one branching alkyl group attached to the carbon chain, which causes the acid to have different physical, and in some cases different chemical, properties than their corresponding straight-chain isomers. For example, stearic acid has a melting point of about 69°C, whereas isostearic acid has a melting point of about 5°C. Some properties of commercial branched-chain acids are shown in Table 1 (1,2). 

Branched-chain acid (common name) CAS Registry Number Molecular weight Boiling point, °C Melting point, °C Approximate price, [kR Producers in the United States 

Manufacturing procedures for most branched-chain acids are well known. For example, oxo process acids are manufactured from branched-chain olefins using hydroformylation followed by oxidation (3) (see Oxo process). 

Neo acids are prepared from selected olefins using carbon monoxide and acid catalyst (4) (see Carboxylic Acids, trialkylacetic acids). 2-EthyIhexanoic acid is manufactured by an aldol condensation of butyraldehyde followed by an oxidation of the resulting aldehyde (5). Isopalmitic acid [4669-02-7] is probably made by an aldol reaction of octanal. 

Isostearic acid is produced from dimerization and reduction of monomeric acids (6). 

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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. 

Branched-Chain Carboxylic Acids. Branched-chain acids such as 2-methylbutyric, 3-methylbutyric, isooctanoic, and isononanoic acids are produced by the oxo reaction, giving first the corresponding aldehyde, which is then oxidized to the acid. 2-EthyIhexanoic acid is produced by the aldol route from butyaldehyde in three steps aldol condensation hydrogenation of the carbon—carbon double bond and oxidation of the branched-chain saturated aldehyde to 2-ethyIhexanoic acid (see Carboxylic Acids, branched-chain acids). 

Table 1. Properties and Prices of Branched-Chain Acids...

Branched-chain acids have a wide variety of industrial uses as paint driers (7), vinyl stabilizers (8), and cosmetic products (9). Cobalt and manganese salts of 2-ethyIhexanoic acid and neodecanoic acid are used as driers for paint, varnishes, and enamels litbium, magnesium, calcium, and aluminum salts of 2-ethyIhexanoic acid are used in the formation of greases and lubricants (see Driers and metallic soaps). Derivatives of isostearic acid have been used as pour point depressants in two-cycle engine oils, as textile lubricants, and in cosmetic formulations. Further industrial appHcations can be found (10). 

The hazards of handling branched-chain acids are similar to those encountered with other aliphatic acids of the same molecular weight. Eye and skin contact as well as inhalation of vapors of the shorter-chain acids should be avoided. 

Branched-Chain Saturated Acids" under "Eatty Acids (Branched-Chain)" in ECT 1st ed., VoL 6, pp. 259—262, by M. D. Reiner (in part), and J. A. Eield (in part). Union Carbide and Carbon Corp. "Branched-Chain Acids" under "Eatty Acids" in ECT 2nd ed., VoL 8, pp. 849—850, by W. C. Ault, U.S. Department of Agriculture "Branched-Chain Acids" under "Carboxylic Acids" in ECT 3rd ed., Vol. 4, pp. 861—863, by R. W. Johnson, Jr., Union Camp Corp. 

In a series of organic acids of similar type, not much tendency exists for one acid to be more reactive than another. For example, in the replacement of stearic acid in methyl stearate by acetic acid, the equilibrium constant is 1.0. However, acidolysis in formic acid is usually much faster than in acetic acid, due to higher acidity and better ionizing properties of the former (115). Branched-chain acids, and some aromatic acids, especially stericaHy hindered acids such as ortho-substituted benzoic acids, would be expected to be less active in replacing other acids. Mixtures of esters are obtained when acidolysis is carried out without forcing the replacement to completion by removing one of the products. The acidolysis equilibrium and mechanism are discussed in detail in Reference 115. 

Homologation of a broad range of aliphatic acid structures and carbon numbers, with extensive rearrangement during the homologation of certain branched-chain acids. 

Massart-Leen et al. (1981) analyzed bovine milk fat and goat milk fat for branched chain fatty acids. They did not find the same diversity of fatty acids in bovine as in goat milk fat and as previously reported. The authors suggested that the difference—the absence of branched chain acids other than iso and anteiso in bovine milk fat—could be caused by the relative inefficiency of the incorporations of methylmalonic acid into the biosynthetic pathway. 

Marine lipids with their diversity of unsaturated and branched chain acid moieties are a difficult class of materials to analyze. Ruminants (sheep, goats, cows, etc.) have a bacterial "factory" in the rumen which is able to produce branched-chain partially-hydrogenated lipids from ingested plant lipids. These lipids are incorporated into the milk and meat of the animals and eventually into animals which feed upon the ruminants. As a rule animal lipids are highly complex in comparison to plant materials. Although the branched chain materials are usually present in low concentration when compared to the common fatty acid moieties, complete description of these fats requires more sophisticated GC and thus long open tubular columns in tandem with mass spectrometry and computer analysis of the data has become an important approach. Even with a 100-m column, subcutaneous lipids of barley-fed lambs were so complex that prior fractionation with urea adducts was necessary (17). 

CARBOXYLICACIDS - BRANCHED-CHAIN ACIDS] (Vol 5) Neodecanoic acid [26896-20-8]... 

Reaction XL. (6) Action of Carbon Monoxide on Alcohols under pressure in Presence of Catalysis. (J. C. S., 1936, 358.)—Acetic acid and higher acids can be formed by the action of carbon monoxide on the alcohol at 330° and 200 atm. in presence of phosphoric acid catalysts. Branched chain acids may be formed from normal alcohols, through the intermediary of the olefines derived from the alcohols by dehydration. 

Whilst straight-chain fatty acids are the most common, branched-chain acids have been found to occur in mammalian systems, e.g. in wool fat and butter fat. They are also characteristic fatty acid constituents of the lipid part of cell walls in some... 

This section deals with acids, that are formally modified aldonic acids, such as keto, deoxy, and branched-chain acids (including the so-called saccharinic acids). The aminoaldonic acids, which are oxidation products of amino sugars, and, in particular, the important nonulosaminic acids (neuraminic acids) and muramic acid, are not discussed here. The formation of saccharinic acids by the treatment of sugars with alkali, and the mechanisms involved, are likewise outside the scope of this chapter. 

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