Sources of Carboxylic Acids

The large-scale preparation of carboxylic acids relies on chemical synthesis. Virtually none of the 3 X 10 lb of acetic acid produced in the United States each year is obtained from vinegar. Most of it comes from the reaction of methanol with carbon monoxide. 

Ants aren t the only insects that use formic acid as a weapon. Some Galerita beetles spray attackers with an 80% solution of it. 

Ethanol is oxidized to acetic acid as wine becomes vinegar. 

Butanoic and hexanoic acid are responsible for the nasty odor of ginkgo seeds. 

Malic acid and citric acid contribute to the tart taste of many fruits and vegetables. 

Many carboxylic acids were first isolated from natural sources and were given names based on their origin. Formic acid (Latin formica, ant ) was obtained by distilling ants. Since ancient times acetic acid (Latin acetum, vinegar ) has been known to be present in wine that has turned sour. Butyric acid (Latin butyrum, butter ) contributes to the odor of both rancid butter and ginkgo berries, and lactic acid (Latin lac, milk ) has been isolated from sour milk. 

The principal end use of acetic acid is in the production of vinyl acetate for paints and adhesives. 

The carboxylic acid produced in the greatest amounts is 1,4-benzenedicarboxylic acid (terephthalic acid). About 5 X 10 Ib/year is produced in the United States as a starting material for the preparation of polyester hbers. One important process converts p-xylene to terephthalic acid by oxidation with nitric acid  

You will recognize the side-chain oxidation of p-xylene to terephthalic acid as a reaction type discussed previously (Section 11.13). Examples of other reactions encountered earlier that can be applied to the synthesis of carboxylic acids are collected in Table 

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Decarboxylation reactions of metal carboxylates [Eq. (1)], are of increasing value in the synthesis of organometallic compounds (1-5). The reverse reaction, e.g., carbonation of Grignard and organolithium reagents (6,7), is a well-known source of carboxylic acids. Early reviews of the... 

Note an intuitive point here. The p-keto esters, which contain a ketone, are the sources of ketones after decarboxylation, and the diesters, which contain only ester carbonyls, are the source of carboxylic acids after decarboxylation (Rg. 19.60). 

TABLE 14.2 Names and Natural Sources of Carboxylic Acids... 

The direct production of platform chemicals from fats and oil can be quicker, more convenient, and logical from an economic point of view. However, the starting material or the biomass component to be used must be clearly known so as to reduce the use of raw materials, reagents, processing steps, and overall the investment cost. For example, fatty acids with O-containing compounds can be directly used as a source of carboxylic acids. Thus the type of biomass/oils and fats used for the production of specific platform chemicals plays a role in the success of platform chemical production. 

For source-reservoir rock systems in the 80 to 130 °C temperature interval, four important and overlapping sources of carboxylic acids/acid anions in the fluid phase have been identified. All four processes are capable of generating significant quantities of water-soluble carboxylic acids/acid anions. Thus, it is not surprising that the alkalinity of the fluid phase in source/ reservoir rock systems in the 80 to 110°C ( 10°C) temperature interval typically is dominated by OAA. 

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