1. Identify the Longest Continuous Chain
- Select the longest chain of carbon atoms as the parent chain.
- If two chains have the same length, choose the one with more substituents.
- The name of the alkane is based on the number of carbon atoms in this chain (e.g., methane, ethane, propane, butane).
2. Number the Carbon Chain
- Number the chain from the end closest to the first substituent (branch) to give it the lowest possible number.
3. Identify and Name the Substituents
- The groups attached to the main chain (branches) are called alkyl groups (e.g., methyl (-CH₃), ethyl (-C₂H₅)).
- If there are multiple substituents of the same type, use prefixes: di- (2), tri- (3), tetra- (4), etc.
4. Assign Numbers to Substituents
- Use the carbon number where the substituent is attached.
- If multiple substituents are present, list them in alphabetical order, ignoring prefixes like di-, tri-, etc.
5. Write the Name in the Correct Format
- The complete name is written as number-position + substituent name + parent alkane.
- Commas separate numbers, and hyphens separate numbers from words.
- Example: 2-methylpentane (a methyl group on carbon 2 of pentane).
6. Naming Complex Substituents
- If a substituent itself has branches, it is named as a separate alkyl group within parentheses.
- Example: 3-(1-methylethyl)hexane (for an isopropyl group on carbon 3 of hexane).
7. Naming Cycloalkanes (If Applicable)
- If the alkane is cyclic, prefix the name with “cyclo-“ (e.g., cyclopentane, cyclohexane).
- Numbering starts from the substituent that comes first in alphabetical order.
Example Names
- CH₄ → Methane
- CH₃CH₃ → Ethane
- CH₃CH₂CH₃ → Propane
- CH₃CH(CH₃)CH₃ → 2-Methylpropane
- CH₃CH₂CH₂CH₃ → Butane
- CH₃CH(CH₃)CH₂CH₃ → 2-Methylbutane
