Alkanes IUPAC Naming Examples

Naming a organic compound is a multi step process and should be done very carefully. But naming alkane is the easiest in among them. When naming alkane, that includes selecting longest carbon chain, identifying substituents, numbering carbon chain properly and some other steps. We will discuss those steps and examples to write IUPAC names of alkanes.

Identify longest continuous carbon chain

Identify longest continuous carbon chain (which includes maximum number of carbon atoms). It is called root chain. Then other carbon atoms which not included in root chain are defined as substituents or branched chains. There are five carbon atoms in the root chain and two substituents in the below organic molecule.

identify longest carbon chain

Naming substituents in IUPAC naming

Some substituents and their substituent names are noted below.

  • -CH3        - methyl
  • -CH2CH3       - ethyl
  • -CH2CH2CH3    - propyl
  • -Br          - bromo
  • -Cl         - chloro

When writing IUPAC name, we first write substituents chain name and then root chain. Don't think about much in this level. You will understand more when examples are discussed.

root chain and substituent chain

Alkane IUPAC naming - Example 1

  1. Select longest carbon chain, root chain which is circled and bold in Fig 2. There are six 6 carbon atoms in the root chain.

  2. Determine substituent(s). Substituents are highlighted (black bold) in fig 2.
    CH3 - methyl
    CH2CH3 - ethyl
    Substituent are named according to alphabetical order, Therefore first comes ethyl group and then methyl group and substituent part is named as below.
    3-ethyl-5-methyl
    root chain and substituent organic compound

  3. Start numbering carbon chain. ethyl group gets lower position because it exists first in the name according to the alphabetical order of substituents. 3-ethyl-5-methylhexane

  4. Write the name finish the name as ane due to six carbon atoms in the chain, finish the name as hexane. Then complete the name
    3-ethyl-5-methylhexane


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