Organic Chemistry

Naming Alkanes

Figure 43 Butane

Figure 44 Isobu-

tane (2-methyl-

propane)

18.6 Naming Alkanes

There are several ways or systems for thenomenclature, or naming, of organic molecules,
but just two main ones.

1.The traditional, non-systematic names. Many of these linger on, especially for simpler

or more common molecules.

2.The systematicIUPAC^3 (eye-YOU-pack (International Union of Pure And Applied

Chemistry)) names.

The IUPAC system is necessary for complicated organic compounds. It gives a series of
unified rules for naming a large compound by conceptually dividing it up into smaller, more
manageable nameable units.

Many traditional (non-IUPAC) names are still commonly used in industry, especially for
simpler and more common chemicals, as the traditional names were already entrenched.

18.7 IUPAC naming rules.

1.Find the longest carbon chain, identify the end near which the most substituents^4 are

located, and number the carbons sequentially from that end. This will be the parent

chain.

2.Consider all other carbon groups as substituents.

3.Alphabetize the substituents.

4.Number the substituents according to the carbon to which they are attached. If

numbering can be done in more than one way, use the numbering system that results

in the smallest numbers.

Substituents are named like a parent, and replacing the-aneending with-yl.

3 http://www.wikipedia.org/wiki/IUPAC
4 https://en.wikipedia.org/wiki/substituent