Commercial Sources of Carboxylic Acids

Acetic acid is also an industrial chemical. It serves as a solvent, a starting material for synthesis, and a catalyst for a wide variety of reactions. Some industrial acetic acid is produced from ethylene, using a catalytic oxidation to form acetaldehyde, followed by another catalytic oxidation to acetic acid. 

Methanol can also serve as the feedstock for an industrial synthesis of acetic acid. The rhodium-catalyzed reaction of methanol with carbon monoxide requires high pressures, so it is not suitable for a laboratory synthesis. 

Some aromatic carboxylic acids are also commercially important. Benzoic acid is used as an ingredient in medications, a preservative in foods, and a starting material for synthesis. Benzoic acid can be produced by the oxidation of toluene with potassium permanganate, nitric acid, or other strong oxidants. 

and other insects often use fatty acids and derivatives as pheromones to attract mates. There is much interest in exploiting these compounds as a means of insect control. 

Hydrolysis of a fat or an oil gives a mixture of the salts of straight-chain fatty acids. Animal fats contain primarily saturated fatty adds, while most vegetable oils are polyunsaturated. 

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Formic acid and acetic acid are the two most important carboxylic acids. Formic acid is a source of irritation in the bites of ants and other insects or in the scratch of nettles. A liquid with a sharp, irritating odor, formic acid is used in manufacturing esters, salts, and plastics. Acetic acid is present in a concentration of about 5% in vinegar and is responsible for its odor and taste. Acetic acid is among the least expensive organic acids, and is therefore a raw material in many commercial processes that require a carboxylic acid. Sodium acetate is one of several common salts of carboxylic acids. It is used to control the acidity of chemical processes and in preparing soaps and pharmaceutical agents. 

A large number of salts of sahcyhc acid have been prepared and evaluated for therapeutic or other commercial use. Table 7 hsts those most frequently referenced. Sodium sahcylate has analgesic, antiinflammatory, and antipyretic activities and was used extensively in the sixteenth and seventeenth centuries as a remedy, prepared from natural sources, for arthritis and rheumatism. In the 1990s the salt can be obtained directly from Kolbe-Schmitt carboxylation or by the reaction of sahcyhc acid with either aqueous sodium bicarbonate or sodium carbonate. The resulting mixture is heated until effervescence stops the salt is then isolated by filtration and evaporation to dryness at low temperatures. Generally, the solution must be kept slightly acidic so that a white product is obtained if the mixture is basic, a colored product results. The USP product contains 99.5—100.5% NaC H O (anhydrous). The May 1996 price was 8.15/kg (18). 

Unless the last-mentioned product is removed by the inclusion of catalase, the oxoacid is liable to react further, undergoing oxidative decarboxylation to the carboxylic acid. An attractive feature of this group of enzymes in the present context is that there exist readily available representatives of both enantiospecificities. The well-studied and commercially available AAOs from vertebrate sources, such as l-AAO from snake venom and D-AAO from pig kidney, are expensive, however, and are increasingly being replaced by enzymes from microbial sources. 

Furan carboxylic acids are usually prepared by ring synthesis using the Feist-Benary and Paal-Knorr methods (Section 3.12.2.2). However, furancarboxylic acids can also be prepared by reaction of lithiofurans with carbon dioxide. A convenient source of furan-3-carboxylic acid (517) is the commercially available diethyl furan-3,4-dicarboxylate (518) (71S545). 

The obvious approach for chiral synthesis would be to find a chiral starting material, such as a natural amino acid, carbohydrates, carboxylic acids or terpene. The major source of these chiral starting materials sometimes called chirons is nature itself. The synthesis of a complex enantiopure chemical compound from a readily available enantiopure substance such as natural amino acids is known as chiral pool synthesis. For example, chiral lithium amides 1.39 that are used for several types of enantioselective asymmetric syntheses can be prepared in both enantiomeric forms starting from the corresponding optically active amino acids, and these are often available commercially. 

Materials. The following were obtained from commercial sources Swims medium S77, horse serum, and fetal calf serum (Grand Island Biologicals) MTX (Lederle Laboratories) was purified by DEAE cellulose prior to use (11) crystalline BSA, poly-L-lysine (M 35,000), hypoxanthine and thymidine (Sigma Chemical Co.) 1-etnyl-3-(3 -dimethylaminopropyl)carbodiimide hydrochloride (EDC) (Story Chemicals) folinic acid (ICN Pharmaceuticals) Blue Dextran (Pharmacia). The concentrations of the folate derivatives and MTX were determined by their respective extinction coefficients (13). MTX-BSA was synthesized according to a previously described procedure ( ) in which MTX is coupled via a terminal carboxyl group to -amino groups contained in the albumin molecule. 

Biosynthetically, purines are built up via formation of the imidazole ring first, from glycine and formate, and thence to hypoxanthine and then the other natural purines. In the laboratory, most imidazole-based purine syntheses start with 5-aminoimidazole-4-carboxylic acid, particularly its amide (known by the acronym AICA), which as well as its riboside, is commercially available from biological sources. The use of 5-aminoimidazole-4-carbonitrile in this approach results in the formation of 6-amino-purines, as in a synthesis of adenine itself." ... 

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