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IUPAC Naming Basics

Note: This is a learning resource and may simplify some concepts for educational purposes.
Scope: This page covers basic alkane naming. Functional groups (like alcohols) follow additional priority rules.

The 4-Step Decision Flow

  1. Identify the Longest Carbon Chain (Parent Chain)

    Count the carbons in the longest continuous chain. This gives the base name (e.g., Propane, Butane, Octane).

  2. Identify the Highest Priority Group

    If there's a functional group (like -OH), it gets priority over simple branches.

  3. Number the Chain

    Number starting from the end that gives the priority group (or first branch) the lowest possible number (locant).

  4. Name the Substituents Alphabetically

    Ethyl comes before Methyl. If you have two methyls, use "dimethyl" (but alphabetize by "m").

Examples

2-methylpropane

Propane: 3-carbon chain.

2-methyl: A methyl group (CH3) attached to the 2nd carbon.

Tricky Case: Tie-Breaker

Scenario: Two chains have the same length?

Rule: Choose the chain that has more substituents (branches). This makes naming simpler.

Next Topic Common Reactions →
Related Topic Functional Groups
Last updated: 2026-01-13

Examples

2-methylpropane

Propane: 3-carbon chain.

2-methyl: A methyl group (CH3) attached to the 2nd carbon.