Naming the Carboxylic Acids

Like other organic compounds, many carboxylic acids have common names that are used frequently in the literature. These names often indicate the natural sources from which the acids were first isolated (Table 19-1). Chemical Abstracts retains the conunon names for the two simplest, formic and acetic acids. The carboxy function and the functional groups of its derivatives take precedence in naming over any other group discussed so far. 

Carboxylic Anhydride Ester Acyl Amide Nitrile Aldehyde Ketone Alcohol Thiol Amine 

From the destructive distillation of ants (formica, Latin, ant) 

Butter (particularly if rancid) (butyrum, Latin, butter) Valerian root Odor of goats 

To the extent possible, any carbon-carbon double or triple bonds that are present should be included in naming the main chain. Saturated cyclic acids are named as cycloalkanecarboxylic acids. Their aromatic counterparts are the benzoic acids. In these compounds, the carbon 

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For each ester in the previous question, name the carboxylic acid and the alcohol that are needed to synthesize it. 

Which of the following alcohols can be oxidized to a carboxylic acid Name the carboxylic acid produced. For those alcohols that cannot be oxidized to a carboxylic acid, name the final product. 

Name the carboxylic acid (either lUPAC or common name) from which the carboxylate salt is derived. 

The main classes of hydroxy compounds are aliphatic alcohols with OH groups attached to sp hybridized carbon atoms and phenols, in which the OH groups are attached to sp carbon atoms located in the aromatic systems. Another group of hydroxy compoimds—namely, the carboxylic acids, having the strucmral fragment COOH is discussed separately. 

In lUPAC names, the carboxylic acid group takes precedence over amino groups. Therefore, C-1 is the carboxyl group, the parent compound is propanoic acid, and the name is therefore 3-aminopropanoic acid. Its common name is (i-alanine, which is a component of pantothenic acid (vitamin B5) and some naturally occurring peptides. 

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... 

Systematic names for carboxylic acids are derived by counting the number of car bons m the longest continuous chain that includes the carboxyl group and replacing the e ending of the corresponding alkane by oic acid The first three acids m Table 19 1 methanoic (1 carbon) ethanoic (2 carbons) and octadecanoic acid (18 carbons) illus trate this point When substituents are present their locations are identified by number... 

All these facts—the observation of second order kinetics nucleophilic attack at the carbonyl group and the involvement of a tetrahedral intermediate—are accommodated by the reaction mechanism shown m Figure 20 5 Like the acid catalyzed mechanism it has two distinct stages namely formation of the tetrahedral intermediate and its subsequent dissociation All the steps are reversible except the last one The equilibrium constant for proton abstraction from the carboxylic acid by hydroxide is so large that step 4 is for all intents and purposes irreversible and this makes the overall reaction irreversible... 

Nitriles can also be named as derivatives of carboxylic acids by replacing the -ic acid or -oic acid ending with -onitrile, or by replacing the -carboxylic acid ending Avith -carbonitriie. The nitrile carbon atom is attached to Cl but is not itself numbered. 

Acid halides are named by identifying first the acyl group and then the halide. The acyl group name is derived from the carboxylic acid name by replacing the -ic acid ending with -yl or the -carboxylic acid ending with -carbonyl, as described previously in Section 20.1 and shown in Table 20.1 on page 753. For example ... 

Esters are named by first identifying the alkyl group attached to oxygen and then the carboxylic acid, with the -ic acid ending replaced by -ate. 

The amino acids link together by the reaction of an amino group of one amino acid with the carboxylic acid group of another amino acid. This forms a peptide bond. (For the sake of clarity the + signs in the reaction have been omitted.) A peptide bond is an amide group in molecules that are not biochemical. Many functional groups have different names in organic chemistry and in biochemistry. 

In humans, ca. 10% of the urinary metabolites of epicainide (4.29, Fig. 4.3), an antiarrhythmic agent, is accounted for by the carboxylic acid derivative 4.32. Three distinct pathways are possible for the formation of this metabolite, namely direct hydrolysis of the secondary amide function of epicainide (Fig. 4.3, Pathway a), hydrolysis of the primary amide (4.30) resulting... 

Like in Chapt. 7, we begin the discussion with acetates, since acetic acid is the simplest nontoxic acyl group, formic acid being less innocuous. An informative study was carried out to compare the kinetics of hydrolysis of two types of corticosteroid esters, namely methyl steroid-21-oates (which are active per se) and acetyl steroid-21-ols (which are prodrugs), as exemplified by methyl prednisolonate (8.69) and prednisolone-21-acetate (8.70), respectively [89]. In the presence of rat liver microsomes, the rate of hydrolytic inactivation of methyl steroid-21-oates was much slower than the rate of hydrolytic activation of acetyl steroid-21-ols. Thus, while the Km values were ca. 0.1 -0.3 mM for all substrates, the acetic acid ester prodrugs and the methyl ester drugs had Vmax values of ca. 20 and 0.15 nmol min-1 mg-1, respectively. It can be postulated that the observed rates of hydrolysis were determined by the acyl moiety, in other words by the liberation of the carboxylic acid from the acyl-enzyme intermediate (see Chapt. 3). 

Draw and name two carboxylic acids with the molecular formula... 

O Draw and name one carboxylic acid and one ester with the molecular formula C6H12O2. 

Pyridine is often used as a solvent in such reactions, since it is also fnnctions as a weak base. As an aromatic base, pyridine will promote ionization of the carboxylic acid to carboxylate, and also react with the other product of the reaction, namely HCl. Withont removal of HCl, the anhydride formed might be hydrolysed under the acid conditions generated. 

Retained names of carboxylic acids may also be modified to name amides, nitriles and aldehydes, by changing the -ic acid ending to -amide, -onitrile or -aldehyde. Names such as formaldehyde, acetonitrile and propionamide result. Of these, only acetonitrile may be treated as a functional parent hydride. 

Nitration of hydroxypropiophenone (7-1) followed by conversion of the phenol to its methyl ether by means of methyl iodide provides the intermediate (7-2) the nitro group is then reduced to the corresponding amine (7-3) by catalytic reduction. The newly introduced amine is then replaced by a nitrile group by successive conversion to the diazonium salt by means of nitrous acid followed by treatment with cuprous cyanide (7-4). Reaction with aluminum chloride removes the methyl ether to afford the ortho acylphenol (7-5). This is converted to the chromone (7-6) as above by reaction with benzoyl chloride and sodium benzoate. The nitrile is next hydrolyzed to the carboxylic acid (7-7) by means of sulfuric acid. The acid is then converted to its acid chloride by means of thionyl chloride and that treated with 2-(A -piperidyl)ethanol (7-8). There is thus obtained flavoxate (7-9) [8], a muscle relaxant whose name reflects its flavone nucleus. 

Common names, such as formic (ant) and butyric (butter) acids, are based on the natural source of the acid. The positions of substituent groups are shown by Greek letters a, y, S, etc. Some have names derived from acetic acid, e.g., (CH,),CCOOH and C H,CH,COOH, are trimethylacetic acid and phenylacetic acid, respectively. Occasionally they are named as carboxylic acids, e.g. 

Acid chlorides are named by replacing the -ic acid ending with -yl choride or replacing the carboxylic acid ending with -carbonyl chloride. 

Amides are named by replacing the -oic acid or -ic acid suffix of the parent carboxylic acids with the suffix -amide, or hy replacing the -carboxylic acid ending with -carboxamide. Alkyl groups on nitrogen atoms are named as substituents, and are prefaced by N-or N,N-, followed by the name(s) of the alkyl group(s). 

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