Naming Organic Compounds: Alkanes

Introduction to Alkanes

• Focus on naming organic compounds, particularly alkanes.
• Naming based on the number of carbon atoms in the parent chain.
• List of basic alkanes:
  • 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 Examples and Rules

Rule 1: Identifying the Parent Chain

• Count the number of carbons in the longest chain to identify the parent chain.
• The parent chain determines the base name (e.g., hexane for six carbons).

Rule 2: Numbering the Chain

• Number the chain such that the substituents have the lowest possible numbers.

Example 1

• Compound: 5-carbon chain with a methyl group on carbon 2.
• Name: 2-methylpentane
• Rule: Use a hyphen to separate numbers from words.

Example 2

• Compound: Hexane with methyl groups on carbons 2 and 3.
• Name: 2,3-dimethylhexane
• Note: Use a comma to separate numbers for multiple substituents.

Advanced Examples and Special Cases

Example 3: Multiple Substituents

• Compound: Hexane with three methyl groups; two on carbon 3 and one on carbon 2.
• Name: 2,3,3-trimethylhexane

Example 4: Prioritizing Alphabetical Order

• Compound: Heptane with a methyl group on carbon 3 and an ethyl group on carbon 4.
• Name: 4-ethyl-3-methylheptane
• Rule: Prioritize alphabetical order over numerical order (E before M).

Example 5: Propyl and Ethyl Groups

• Compound: Octane with a propyl group on carbon 4 and an ethyl group on carbon 5.
• Name: 4-ethyl-5-propyloctane
• Observation: Alphabetical order takes precedence; order numbers if possible.

Example 6: Ignoring Prefixes in Alphabetical Order

• Compound: Hexane with two methyl groups on carbon 2 and an ethyl group on carbon 4.
• Name: 4-ethyl-2,2-dimethylhexane
• Rule: Ignore prefixes (di-, tri-) when determining alphabetical order.

Additional Resources

• Check the description for links to related materials and exam preparation videos.
• Useful for students studying Organic Chemistry I and II.

Conclusion

• Naming alkanes involves identifying the parent chain, correctly numbering carbon atoms, and organizing substituents by alphabetical order.
• It is essential to understand the prioritization of rules in complex naming scenarios.