11.1 Naming Carboxylic Acids, Nitriles and Carboxylic Acid Derivatives

Carboxylic Acids, RCO2H

Simple carboxylic acids derived from open-chain alkanes are systematically named by replacing the terminal –e of the corresponding alkane name with –oic acid. The –CO2H carbon atom is numbered C1.

The structures of propanoic acid, 4-methylpentanoic acid, and 3-ethyl-6-methyloctane dioic acid. The carbon atoms are numbered and substituents are highlighted.Compounds that have a –CO2H group bonded to a ring are named using the suffix –carboxylic acid. The CO2H carbon is attached to C1 in this system and is not itself numbered. As a substituent, the CO2H group is called a carboxyl group.

The structures of trans-4-hydroxycyclohexanecarboxylic acid and 1-cyclopentenecarboxylic acid. The carbon atoms in both structures are numbered.Because many carboxylic acids were among the first organic compounds to be isolated and purified, quite a few common names exist (Table 11.1). Biological chemists, in particular, make frequent use of these names, so you may find yourself referring back to this list on occasion. We’ll use systematic names in this book, with a few exceptions such as formic (methanoic) acid and acetic (ethanoic) acid, whose names are accepted by IUPAC and are so well known that it makes little sense to refer to them any other way.

Also listed in Table 11.1 are the names of acyl groups The structure of the acyl group where C is double bonded to an O and single bonded to R and any other atom. derived from the parent acids. Except for the eight entries at the top of Table 11.1, whose names have a –yl ending, all other acyl groups are named using an –oyl ending.

Table 11.1 Common Names of Some Carboxylic Acids and Acyl Groups

Structure

Name

Acyl group

HCO2H

Formic

Formyl

CH3CO2H

Acetic

Acetyl

CH3CH2CO2H

Propionic

Propionyl

CH3CH2CH2CO2H

Butyric

Butyryl

HO2CCO2H

Oxalic

Oxalyl

HO2CCH2CO2H

Malonic

Malonyl

HO2CCH2CH2CO2H

Succinic

Succinyl

HO2CCH2CH2CH2CO2H

Glutaric

Glutaryl

HO2CCH2CH2CH2CH2CO2H

Adipic

Adipoyl

H2C═CHCO2H

Acrylic

Acryloyl

HO2CCH═CHCO2H

Maleic (cis) Fumaric (trans)

Maleoyl Fumaroyl

HOCH2CO2H

Glycolic

Glycoloyl
The structure of lactic acid, a propanoic acid with a hydroxyl group attached to C 2.

Lactic

Lactoyl

The structure of pyruvic acid (2-oxopropanoic acid).

Pyruvic

Pyruvoyl

The structure of glyceric acid (2,3-dihydroxypropanoic acid).

Glyceric

Glyceroyl

The structure of malic acid (2-hydroxybutanedioic acid).

Malic

Maloyl

The structure of oxaloacetic acid (oxobutanedioic acid).

Oxaloacetic

Oxaloacetyl

The structure of benzoic acid. A C O O H group is attached to the C 1 of the benzene ring.

Benzoic

Benzoyl

The structure of phthalic acid. Two C O O H groups are connected to the benzene ring's C 1 and C 2.

Phthalic

Phthaloyl

Nitriles, RC≡N

Compounds containing the –C≡N functional group are called nitriles and can undergo some chemistry similar to that of carboxylic acids. Simple open-chain nitriles are named by adding –nitrile as a suffix to the alkane name, with the nitrile carbon numbered C1.

The structure of 4-methylpentanenitrile. C 1 belongs to the C N group. A methyl group is attached to C 4. All the carbon atoms are numbered.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 with –carbonitrile. The nitrile carbon atom is attached to C1 but is not itself numbered.

The structures of acetonitrile (from acetic acid), benzonitrile (from benzoic acid), and 2,2-dimethylcyclohexanecarbonitrile (from 2,2-dimethylcyclohexane-carboxylic acid).If another carboxylic acid derivative is present in the same molecule, the prefix cyano– is used for the C≡N group.

The structure of methyl-4-cyanopentanoate. Cyano group is attached to C 4. The C 1 is double-bonded to an O atom and single-bonded to the O C H 3 group.Problem 11.1
Give IUPAC names for the following compounds:

(a)

The structure of 3-methylbutanoic acid, which has a C O O H group on C 1 and a methyl group on C 3 of a four-carbon chain.

(b)

The structure of 4-bromopentanoic acid, which has a C O O H group on C 1 and a bromine atom on C 4 of a five-carbon chain.

(c)

The structure of 2-ethylpentanoic acid, which has a C O O H group on C 1 and an ethyl on C 2 of a five-carbon chain.

(d)

The structure of (Z)-hex-4-enoic acid with six-carbon atoms. There is a C O O H on C 1, and C 4 and C 5 are double bonded with cis arrangement.

(e)

The structure of 2,4-dimethylpentane, which is a five-carbon chain in which C 1 is part of a C N group. There are methyl groups on C 2 and C 4.

(f)

The structure of cyclopentane-1,3-dicarboxylic acid with cyclopentane ring. There are C O O H groups on C 1 and C 3, positioned cis to each other.

Problem 11.2
Draw structures corresponding to the following IUPAC names:

(a) 2,3-Dimethylhexanoic acid

(b) 4-Methylpentanoic acid

(c) trans-1,2-Cyclobutanedicarboxylic acid

(d) o-Hydroxybenzoic acid

(e) (9Z,12Z)-9,12-Octadecadienoic acid

(f) 2-Pentenenitrile

Acid Halides, RCOX

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 or –oic acid ending with –oyl, or the –carboxylic acid ending with –carbonyl. To keep things interesting, however, IUPAC recognizes eight exceptions for which a –yl rather than an –oyl ending is used: formic (formyl), acetic (acetyl), propionic (propionyl), butyric (butyryl), oxalic (oxalyl), malonic (malonyl), succinic (succinyl), and glutaric (glutaryl).

The structures of three acid halides. The first is acetyl chloride, the second is benzoyl bromide, and the third is cyclohexanecarbonyl chloride.

Acid Anhydrides, RCO2CORʹ

Symmetrical anhydrides of unsubstituted monocarboxylic acids and cyclic anhydrides of dicarboxylic acids are named by replacing the word acid with anhydride.

The structures of three acid anhydrides. The first is acetic anhydride, the second is benzoic anhydride, and the third is succinic anhydride.Unsymmetrical anhydrides—those prepared from two different carboxylic acids—are named by listing the two acids alphabetically and then adding anhydride.

The structure of acetic benzoic anhydride which comprises of two carbonyl groups linked by an oxygen atom. A methyl group is attached to one of the carbonyls and a benzene ring to the other.

Esters, RCO2Rʹ

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 structures of three esters. The first is ethyl acetate, the second is dimethyl malonate, and the third is tert-butyl cyclohexane carboxylate.

Amides, RCONH2

Amides with an unsubstituted –NH2 group are named by replacing the –oic acid or –ic acid ending with –amide, or by replacing the –carboxylic acid ending with –carboxamide.

The structures of three amides. The first is acetamide, the second is hexanamide, and the third is cyclopentane carboxamide.If the nitrogen atom is further substituted, the compound is named by first identifying the substituent groups and then the parent amide. The substituents are preceded by the letter N to identify them as being directly attached to nitrogen.

The structures of a secondary and a tertiary amide. The first structure is N-methylpropanamide and the second is N, N-diethylcyclohexanecarboxamide.

Thioesters, RCOSRʹ

Thioesters are named like the corresponding esters. If the related ester has a common name, the prefix thio– is added to the name of the carboxylate: acetate becomes thioacetate, for instance. If the related ester has a systematic name, the –oate or –carboxylate ending is replaced by –thioate or –carbothioate: butanoate becomes butanethioate and cyclohexanecarboxylate becomes cyclohexanecarbothioate, for instance.

The structures of three thioesters. The first is methyl thioacetate, the second is ethyl butanethioate, and the third is methyl cyclohexanecarbothioate.

Acyl Phosphates, RCO2PO32– and RCO2PO3Rʹ–

Acyl phosphates are named by citing the acyl group and adding the word phosphate. If an alkyl group is attached to one of the phosphate oxygens, it is identified after the name of the acyl group. In biological chemistry, acyl adenosyl phosphates are particularly common.The structures of two acyl phosphates. The first is benzoyl phosphate and the second structure is acetyl adenosyl phosphate.A summary of nomenclature rules for carboxylic acid derivatives is given in Table 11.2.

Table 11.2 Nomenclature of Carboxylic Acid Derivatives

Functional group

Structure

Name ending

Carboxylic acid

The structure of a carboxylic acid where an R group is attached to a carbonyl group which in turn is attached to a hydroxyl group.

-ic acid

(-carboxylic acid)

Acid halide

The structure of an acid halide where an R group is attached to a carbonyl group which in turn is attached to an X group.

-oyl halide

(-carbonyl halide)

Acid anhydride

The structure of an acid anhydride where two carbonyl groups are linked by an oxygen atom. An R group is attached to one of the carbonyls and an R dash group to the other.

anhydride

Amide

 The structure of an amide where an R group and an amino groups are connected to a carbonyl carbon.

-amide

(-carboxamide)

Ester

The structure of an ester where an R group is attached to a carbonyl group which in turn is attached to an O R dash group.

-oate

(-carboxylate)

Thioester

The structure of a thioester where an R group is attached to a carbonyl group which in turn is attached to an S R dash group.

-thioate

(-carbothioate)

Acyl phosphate

 The structure of an acyl phosphate where an R group is attached to a carbonyl group which in turn is attached to an O P O 3 group.

-oyl phosphate

Problem 11.3
Give IUPAC names for the following substances:

(a)

The structure shows an acid chloride with a five-carbon chain. A methyl group is attached to C 4 The chlorine atom is attached to the carbonyl carbon.

(b)

The structure shows a cyclohexane ring with a side chain C H 2 C O N H 2 attached to the first carbon.

(c)

The structure shows an ester with seven carbon atoms. An isopropyl group is attached to the carbonyl carbon and another isopropyl group is attached to the ester oxygen.

(d)

The structure shows a benzene ring attached to a carbonyl group enclosed in parentheses with a subscript two. The carbonyl carbon is single-bonded to an oxygen atom.

(e)

The structure of an ester shows a cyclopentane ring attached to a carbonyl group which in turn is attached to an oxygen atom bound to an isopropyl group.

(f)

The structure of an ester shows a cyclopentane ring attached to an oxygen atom which in turn is bound to a carbonyl group bearing an isopropyl group.

(g)

The structure shows a five-carbon chain amide with a double bond between the fourth and fifth carbon. An N-methyl group is attached to the carbonyl carbon.

(h)

The structure shows a three-carbon chain of an acyl phosphate. A hydroxyl group (dash-wedged) and hydrogen atom (wedged) are attached to the second carbon. The phosphate group is attached to the carbonyl carbon.

(i)

The structure shows a thioester where thioethyl and 2,3-dimethylbut-2-ene groups are attached to the carbonyl carbon.

Problem 11.4
Draw structures corresponding to the following names:

(a) Phenyl benzoate

(b) N-Ethyl-N-methylbutanamide

(c) 2,4-Dimethylpentanoyl chloride

(d)Methyl 1-methylcyclohexanecarboxylate

(e) Ethyl 3-oxopentanoate

(f) Methyl p-bromobenzenethioate

(g) Formic propanoic anhydride

(h) cis-2-Methylcyclopentanecarbonyl bromide

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