Organic Chemistry: Concepts and Applications - Headley Allan D. 2020
Heteroatomic Functional Groups and Organic Nomenclature
3.13 Structure and Properties of Amides
The amide functional group is found in various molecules, not only in organic chemistry but also in biochemistry and biology. Proteins and peptides are important molecules to life, which are amides and some very useful polymers are polyamides. The amide functionality consists of a carbonyl group that is bonded to an sp3 nitrogen. It is possible to have two hydrogens bonded to the nitrogen of the amide functionality; one hydrogen atom and one alkyl group; or two alkyl groups. Amides can be described as primary, secondary, or tertiary based on the number of hydrogens or alkyl groups bonded to the nitrogen as illustrated below.
Shown below is the amide bond as part of a dipeptide.
3.13.1 Nomenclature of Amides
In naming primary amides, identify the longest chain that contains the amide functional group and assign the carbonyl carbon #1, as illustrated below.
The root name of an amide is based on the number of carbons of the corresponding alkane — the alkane is changed to alkanamide. Thus, the root name for the molecule above is pentanamide and not butanamide. Since the amide functionality is a terminal functionality, it is not necessary to indicate its position by #1. The position of any group (substituent) must be specified by a number based on the numbering system used to determine the longest chain. Thus, the complete IUPAC name of the primary amide above is shown below, along with an example of the IUPAC name of another primary amide.
In naming secondary and tertiary amides, the substituents of the nitrogen are named and specified by the prefix, N; examples are shown below.
If there are substituents on the longest chain, they are specified based on the numbers assigned to derive the root name of the molecule. Examples are shown below.
Problem 3.24
i. Give IUPAC names of the following amides.
ii. Give the structures for the molecules below.
a) N,N-Diethyl-3-methylpentanamide |
b) 2,2,3-Trimethylhexanamide |