Naming Organic Compounds - Alkanes

Introduction

• Focus on naming organic compounds, specifically alkanes.
• Start with identifying the number of carbons to find the parent chain.
• Naming is based on the number of carbons:
  • 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 Process

1. Identify the Parent Chain: Count the number of carbon atoms in the longest chain.
2. Number the Chain: Number in the direction that gives substituents the lowest numbers.
   • Substituents are groups attached to the main chain (e.g., methyl group).
3. Naming Substituents:
   • Use hyphens to separate numbers from words.
   • Use commas to separate multiple numbers.
   • Use 'di', 'tri', 'tetra' for multiple identical substituents (e.g., dimethyl for two methyl groups).

Examples

Example 1

• 2-Methylpentane:
  • Parent chain: Pentane (5 carbons)
  • Methyl group at carbon 2.

Example 2

• 2,3-Dimethylhexane:
  • Parent chain: Hexane (6 carbons)
  • Methyl groups at carbons 2 and 3.
  • Use 'di' for two methyl groups.

Example 3

• 4-Ethyl-3-Methylheptane:
  • Parent chain: Heptane (7 carbons)
  • Ethyl group at carbon 4, Methyl group at carbon 3.
  • Alphabetical order: Ethyl (E) comes before Methyl (M).
  • Ascending order of numbers is less important than alphabetical order.

Example 4

• 5-Ethyl-4-Propyl-Octane:
  • Parent chain: Octane (8 carbons)
  • Ethyl group at carbon 5, Propyl group at carbon 4.
  • Substituents in alphabetical order (E before P).
  • Numbering can go left-to-right or right-to-left, but alphabetical order takes priority.

Example 5

• 4-Ethyl-2,2-Dimethylhexane:
  • Parent chain: Hexane (6 carbons)
  • Ethyl group at carbon 4, two methyl groups at carbon 2.
  • Ignore prefixes (di) for alphabetical ordering; consider E and M.
  • Correct order: Ethyl before Methyl.

Additional Resources

• Links to further videos and exam preparation materials are available in the video description.
• Organic chemistry exam preparation videos can be accessed via provided links.

Key Takeaways

• Always identify the longest carbon chain first.
• Number the chain to give the lowest numbers to substituents.
• Prioritize alphabetical ordering of substituents over ascending numerical order.
• Ignore numerical prefixes when alphabetizing substituents.

These notes summarize the key points of naming alkanes covered in the lecture, helpful for review and study for exams.