Common names of carboxylic acids

It IS hard to find a class of compounds in which the common names of its members have influenced organic nomenclature more than carboxylic acids Not only are the common names of carboxylic acids themselves abundant and widely used but the names of many other compounds are derived from them Benzene took its name from benzoic acid and propane from propionic acid not the other way around The name butane comes from butyric acid present m rancid butter The common names of most aldehydes are derived from the common names of carboxylic acids—valeraldehyde from valeric acid for exam pie Many carboxylic acids are better known by common names than by their systematic ones and the framers of the lUPAC rules have taken a liberal view toward accepting these common names as permissible alternatives to the systematic ones Table 19 1 lists both common and systematic names for a number of important carboxylic acids... 

Nitrile names are formed from common names of carboxylic acids. 

Alkanamide (-amide replaces the -oic acid ending of the I.U.P.A.C. name of carboxylic acid) Alkanamide (-amide replaces the -ic acid ending of the common name of carboxylic acid)... 

Common names of aldehydes are derived from the common names of carboxylic acids (Table 18-2). These names often reflect the Latin or Greek term for the original source of the acid or the aldehyde. Greek letters are used with common names of aldehydes to give the locations of substituents. The first letter (a) is given to the carbon atom next to the carbonyl group. 

The common name for an aldehyde is derived from the common name of the corresponding carboxylic acid by dropping the word acid and changing the suffix -ic or -oic to -aldehyde. Because we have not yet studied common names for carboxylic acids, we are not in a position to discuss common names for aldehydes. We can, however, illustrate how they are derived by reference to two common names of carboxylic acids with which you are familiar. The name formaldehyde is derived from formic acid, and the name acetaldehyde from acetic acid ... 

The common names of carboxylic acids with one to four carbon atoms are formic acid, acetic acid, propionic acid, and butyric acid. 

Common names for carboxylic acids are derived from Latin or Greek words that indicate one of their naturally occurring sources. Table 7-1 lists the common name, structure, source, and etymology for some common carboxylic acids. 

Common Names of Dicarboxylic Acids A dicarboxylic acid (also called a diacid) is a compound with two carboxyl groups. The common names of simple dicarboxylic acids are used more frequently than their systematic names. A common mnemonic for these names is Oh my, such good apple pie, standing for oxalic, malonic, succinic, glutaric, adipic, and pimelic acids. The names and physical properties of some dicarboxylic acids are given in Table 20-2. 

Common names of nitriles are derived from the corresponding carboxylic acids. Begin with the common name of the acid, and replace the suffix -ic acid with the suffix -onitrile. The IUPAC name is constructed from the alkane name, with the suffix -nitrile added. 

The names of carboxylic acid derivatives are formed from the names of the parent carboxylic acids discussed in Section 19.2. Keep in mind that the common names formic acid, acetic add, and benzoic acid are virtually always used for the parent acid, so these common parent names are used for their derivatives as well. 

A cyclic ester is called a lactone. The lUPAC name of a lactone is formed by dropping the suffix -oic acid from the name of the parent carboxylic acid and adding the suffix -olactone. The common name is similarly derived. The location of the oxygen atom in the ring is indicated by a number if the lUPAC name of the acid is used and by a Greek letter a, y, d, B, and so forth if the common name of the acid is used. 

There are many carboxylic acids, and they are found in such common products as vinegar and lemon juice (lemon juice contains citric acid see structure 10 in Chapter 1, Section 1.1). Two simple examples of carboxylic acids are 73, which has the common name of formic acid (found in some ant venoms), and 72, which has the common name acetic acid (a dilute solution in water is called vinegar). Lactic acid (74 the lUPAC name is 2-hydroxypropanoic acid) is found in sour milk. An urban myth claims that lactic acid is responsible for muscle soreness after strenuous exercise however, this has been disproved, although it is involved in metabolism. 

Esters such as 59 are essentially a combination of a carboxylic acid and an alcohol. The acid part (RCO in 59) is named after the parent carboxylic acid and the alcohol part (OR in 59) is named after the alcohol. To make it work, the alcohol part is treated as an alkyl substituent, so an ester with a methanol component is a methyl ester and an ester with a propanol component is a propyl ester. This alcohol part of the name is followed by the acid part, where the oic acid part of the name is replaced by oate. Ethyl hexanoate is the name of 65 (from ethyl alcohol—ethanol—and hexanoic acid) ethyl ethano-ate (MeCOgEt, 66) is another example. Ethyl ethanoate is a special case in the sense that it is derived from ethanoic acid, which has the common name of acetic acid. Therefore, 66 has a common name that is used most often ethyl acetate. Note the shorthand way of writing ethyl acetate EtOAc, where Et is ethyl and OAc is the acetate unit OgCCHg. 

FIGURE 14.1 The lUPAC names of carboxylic acids use the alkane names but replace e with oic acid. Q What is the lUPAC and common name of a carboxylic acid with a chain of four carbons ... 

The name of an ester consists of two words that are derived from the names of the alcohol and the acid in that ester. The first word indicates the alkyl part from the alcohol. The second word is the carboxylate part from the carboxylic acid. The lUPAC names of esters use the lUPAC names for the carbon chain of the acid, while the common names of esters use the common names of the acids. Let s take a look at the following ester, which has a fruity odor. We start by separating the ester bond into two parts, which gives us the alkyl of the alcohol and the carboxylate of the acid. Then we name the ester as an alkyl carboxylate (see Figure 17.7). 

Change the ic acid in the acid name to ate. The carboxylic acid with three carbon atoms is propanoic acid. Replacing the ic acid with ate gives the lUPAC name propyl propanoate. The common name of propionic acid gives the common name for the ester of propyl propionate. 

The list of carboxylic acids in Table 19 1 is by no means exhaus tive insofar as common names are concerned Many others are known by their common names a few of which follow Give a systematic lUPAC name for each... 

The common method of naming aldehydes corresponds very closely to that of the related acids (see Carboxylic acids), in that the term aldehyde is added to the base name of the acid. For example, formaldehyde (qv) comes from formic acid, acetaldehyde (qv) from acetic acid, and butyraldehyde (qv) from butyric acid. If the compound contains more than two aldehyde groups, or is cycHc, the name is formed using carbaldehyde to indicate the functionaUty. The lUPAC system of aldehyde nomenclature drops the final e from the name of the parent acycHc hydrocarbon and adds al If two aldehyde functional groups are present, the suffix -dialis used. The prefix formjlis used with polyfunctional compounds. Examples of nomenclature types are shown in Table 1. 

Table 20.1 Common Names of Some Carboxylic Acids and Acyl Groups...

When naming carboxylic acids, the final -e of the hydrocarbon is replaced with either -ic acid (common name) or -oic acid (lUPAC name). The carbonyl carbon on the acid is position one. When naming the salts, the -ic of the acid name is replaced with -ate. 

Figure 12-1 shows the structures of some carboxylic acids, and their common names and lUPAC names are given in the following list. Figure 12-2 shows the structures and names of some of carboxylic acid salts. 

Similar to inorganic acids, the reaction of carboxylic acids and bases produces carboxylic acid salts. Several of these salts are commonly used in foods and beverages as preservatives. The most common are salts from benzoic, propionic, and sorbic acids. The salts of these acids have names ending with ate, and can often be found in the list of ingredients of baked goods and fruit drinks. Several common preservatives are shown in Figure 15.11. 

The nomenclature for this homologous series is somewhat confused. The term PANs has been used historically to denote peroxyacyl nitrates, and this terminology continues to be used extensively in the literature, despite the lack of adherence to traditional IUPAC rules of nomenclature. Because the PANs can be considered to be mixed anhydrides of carboxylic acids and nitric acid, another suggestion (Roberts, 1990) has been peroxyacetic nitric anhydride for CH,C(0)00NO2 and peroxy carboxylic nitric anhydrides for the whole class of compounds. Although it does not follow the IUPAC rules, it would be consistent with the widespread use of the name PAN but also reflect the structure more accurately. Table 6.20 shows the structures and commonly used names of some PANs that have been observed in the atmosphere and/or in laboratory studies. 

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