NAMING STEPS
The primary goal of the International Union of Pure and Applied Chemistry (IUPAC) naming
system is to create an unambiguous relationship between the name and structure of a compound.
With the conventions established by IUPAC, no two distinct compounds have the same name. The
IUPAC naming system greatly simplifies chemical naming. Once we understand the rules, we can
match names to structures with ease.
1. Identify the Longest Carbon Chain Containing the Highest-Order
Functional Group
This will be called the parent chain and will be used to determine the root of the name. Keep in
mind that if there are double or triple bonds between carbons, they must be considered when
identifying the highest-order functional group. We’ll examine priorities of functional groups
throughout this chapter, but keep in mind that the highest-priority functional group (with the most
oxidized carbon) will provide the suffix. This step may sound easy, but be careful! The molecule may
be drawn in such a way that the longest carbon chain is not immediately obvious. If there are two or
more chains of equal length, then the more substituted chain gets priority as the parent chain.
Figure 1.1 shows a hydrocarbon with the longest chain labeled.
Figure 1.1. Finding the Longest Carbon Chain2. Number the Chain
In order to appropriately name a compound, we need to number the carbon chain, as shown in
Figure 1.2. As a convention, the carbon numbered 1 will be the one closest to the highest-priority
functional group. If the functional groups all have the same priority, numbering the chain should
make the numbers of the substituted carbons as low as possible.