Nomenclature of carboxylic acids

Carboxylic acids have common names derived from Latin or Greek words that relate to their natural sources. For example, formic acid is obtained from ant secretions, in Latin, ant is formica hence the name formic acid. The names of acetic acid (acetum, vinegar), butyric acid (butyrum, butter) and stearic acid (stear, tallow) are derived in the same way. 

Number of Carbon Structure Common Name Source 

3 ch3ch2cooh Propionic acid Milk, butter, and cheese (Greek protos, first pion, fat) 

5 CH3(CH2)3COOH Valeric acid Valerian root (L. valere, being strong) 

7 CH3(CH2)5COOH Enanthoic acid Enantic (L. oenanthe, vine blossom) 

1 TABLE 20-1 Names and Physical Properties of Some Carboxylic Acids I  

In common names, the positions of substituents are named using Greek letters. Notice that the lettering begins with the carbon atom adjacent to the carboxyl carbon, the a carbon. With common names, the prefix iso- is sometimes used for acids ending in the —CH(CH3)2 grouping. 

The lUPAC nomenclature for carboxylic acids uses the name of the alkane that corresponds to the longest continuous chain of carbon atoms. Tlie final -e in the alkane name is replaced by the suffix -oic acid. The chain is numbered, starting with the carboxyl carbon atom, to give positions of substituents along the chain. In naming, the carboxyl group takes priority over any of the functional groups discussed previously. 

Unsaturated acids are named using the name of the corresponding alkene, with the final -e replaced by -oic acid. The carbon chain is numbered starting with the carboxyl carbon, and a number gives the location of the double bond. The stereochemical terms cis and trans (and Z and E) are used as they are with other alkenes. Cycloalkanes with — COOH substituents are generally named as cycloalkanecarboxylic acids. 

Aromatic acids of the form Ar—COOH are named as derivatives of benzoic acid, Ph—COOH. As with other aromatic compounds, the prefixes ortho-, meta, and porn- may be used to give the positions of additional substituents. Numbers are used if there are more than two substituents on the aromatic ring. Many aromatic acids have historical names that are unrelated to their structures. 

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The nomenclature of carboxylic acids and their derivatives was discussed in Section 7-6. Many carboxylic acids have trivial names and often are referred to as fatty acids. This term applies best to the naturally occurring straight-chain saturated and unsaturated aliphatic acids, which, as esters, are constituents of the fats, waxes, and oils of plants and animals. The most abundant of these fatty acids are palmitic, stearic, oleic, and linoleic acids. 

Nomenclature of Carboxylic Acid Salts Salts of carboxylic acids are named simply by naming the cation, then naming the carboxylate ion by replacing the -ic acid part of the acid name with -ate. The preceding example shows that sodium hydroxide reacts with acetic acid to form sodium acetate. The following examples show the formation and nomenclature of some other salts ... 

Table 22.2 summarizes the most important points about the nomenclature of carboxylic acid derivatives. 

Summary Nomenclature of Carboxylic Acid Derivatives and Nitriles... 

Nomenclature of Carboxylic Acids Section 12.2A (a) 2,4-dichlorobenzoic acid (b) p-nitrobenzoic acid ... 

Nomenclature of Carboxylic Acid Salts Section 12.4D (a) sodium butanoate (b) calcium ethanoate ... 

Seeing the Structure and Nomenclature of Carboxylic Acids and Derivatives... 

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