Naming Organic Compounds: Focus on Alkanes

Basics of Alkanes Naming

• Identify the number of carbons in the parent chain.
• Common names based on carbon atoms:
  • 1 carbon: Methane
  • 2 carbons: Ethane
  • 3 carbons: Propane
  • 4 carbons: Butane
  • 5 carbons: Pentane
  • 6 carbons: Hexane
  • 7 carbons: Heptane
  • 8 carbons: Octane
  • 9 carbons: Nonane
  • 10 carbons: Decane

Naming Steps

1. Identify the Longest Chain: The parent chain is the longest carbon chain.
2. Number the Chain: Count the carbon atoms in such a way that substituents get the lowest possible numbers.
3. Identify and Name Substituents: Name groups attached to the parent chain, using terms like methyl, ethyl, etc.
4. Construct the Name:
   • Use the format: number-substituentnameparentname.
   • Use hyphens to separate numbers from words.
   • Use commas to separate numbers.

Examples

Example 1

• Compound: 6 carbon parent chain with a methyl group on carbon 2.
• Name: 2-methylhexane

Example 2

• Compound: 5 carbon parent chain with methyl groups on carbon 2 and 3.
• Name: 2,3-dimethylpentane

Example 3

• Compound: 6 carbon parent chain with three methyl groups on carbon 2 and 3.
• Name: 2,3,3-trimethylhexane

Example 4

• Compound: 7 carbon parent chain with a methyl group on carbon 3 and an ethyl group on carbon 4.
• Name According to Rules: 4-ethyl-3-methylheptane
  • Ethyl comes before methyl alphabetically.

Example 5

• Compound: 8 carbon parent chain with a propyl on one end and an ethyl on the other.
• Name: 4-ethyl-5-propyloctane
  • Alphabetical order is prioritized over numeric order.

Example 6

• Compound: Hexane parent chain with two methyl groups on carbon 2 and an ethyl group on carbon 4.
• Name: 4-ethyl-2,2-dimethylhexane
  • Alphabetical order (ignoring prefixes) is prioritized over numeric order.

Important Rules

• Alphabetical Order: Always prioritize arranging substituents alphabetically, ignoring any prefixes such as di-, tri-, tetra-.
• Lowest Numbers for Substituents: Aim for the lowest possible numbers for substituents when numbering the chain.

Additional Resources

• Check video description for links to Organic Chemistry final exam preparation videos and other helpful videos.