14.3: Nomenclature of Carboxylic Acid Derivatives: Amides and Nitriles
The IUPAC and common names of amides are derived from the parent carboxylic acid, by replacing the suffix “oic acid” and “ic acid,” respectively, with “amide.” In the following example, the IUPAC name ethanamide is derived from ethanoic acid, and the common name, acetamide, is obtained from acetic acid.
Alkyl groups bonded to the nitrogen atom of amides are specified as N-alkyl or N,N-dialkyl, with the groups listed in alphabetical order.
For example, if the nitrogen atom is bonded to a methyl group, the IUPAC name is N-methylethanamide, and the common name is N-methylacetamide.
If the nitrogen atom is attached to two identical groups, like two methyl groups, the IUPAC name is N,N-dimethylethanamide, and the common name is N,N-dimethylacetamide.
However, if the two groups are different such as a methyl group and an ethyl group, the IUPAC name is N-ethyl-N-methylethanamide, and the common name is N-ethyl-N-methylacetamide.
When an amide group is attached to a ring the suffix “carboxylic acid” is replaced with “carboxamide.” For example, if the amide group is bonded to cyclohexane, the resulting compound is called cyclohexanecarboxamide, obtained from the parent cyclohexanecarboxylic acid.
Cyclic amides, also called lactams, are named by substituting the suffix “ic acid” of the parent acid with “olactam.” For instance, the IUPAC name of the cyclic four-membered ester shown below is butanolactam, derived from butanoic acid, and the common name is butyrolactam, obtained from butyric acid.
For IUPAC names, the location of the oxygen atom on the ring is indicated by numbering the carbons starting from the carbonyl carbon. The number is added as a prefix, and the name butanolactam becomes 4-butanolactam.
In case of common names, the number is replaced by a Greek letter; however, the carbon atom adjacent to the carbonyl carbon is labelled first, giving the name γ-butyrolactam.
The IUPAC names of nitriles are derived by adding the suffix “nitrile” to the parent alkane. In the following example, the IUPAC name ethanenitrile is derived from the parent ethane.
For common names, the suffix “ic acid” of the parent acid is substituted with “onitrile.”As shown below, the common name, acetonitrile, is obtained from acetic acid.
If the nitrile group is attached to a cycloalkane ring, the parent cycloalkane is named first, followed by the suffix “carbonitrile.“ For example, if the nitrile group is bonded to cyclohexane, the compound is called cyclohexanecarbonitrile, obtained from the parent cyclohexanecarboxylic acid.