Organic Chemistry Lecture: Naming Complex Substituents

Introduction

• Topic: Naming Complex Substituents
• Previous Lesson: Naming Alkanes
  • Reviewed rules for numbering longest continuous chain
  • Proper chain locators for simple substituents
• Complex Substituents: Not simple like methyl, ethyl, etc.
  • Have common names and systematic names

Complex Substituents

• Types:
  • Some have common names
  • All have systematic names

Example and Process

• Simple Substituent Example:
  • Ethyl group: 2 carbons
  • Propyl group: 3 carbons
• Complex Substituent Example:
  • When branched, e.g., not straight butyl
  • Naming Process:
    • Circle parent chain and complex substituent
    • Identify carbon attached to main chain as #1
    • Number longest chain within substituent
    • Name branches off the substituent

Naming Systematically

• Example: 1,2-dimethylpropyl
• Use Parentheses: To differentiate chain locators and substituents

Alphabetizing and Special Cases

• Alphabetizing:
  • Complex substituents alphabetized by first letter in parentheses
  • Common names do not use hyphens (e.g., isobutyl)
• Special Cases:
  • Isomers and common names for 3-4 carbon substituents
  • Common names include isopropyl, isobutyl, sec-butyl, tert-butyl

Complex Examples

• Example with Ethyl and Complex Substituents:
  • Analyze symmetry for numbering
  • Determine longest chain
  • Account for complex substituent systematically

Systematic vs. Common Names

• Systematic Naming:
  • Always place in parentheses
  • Alphabetized by first letter inside parentheses

Conclusion

• Have a grasp on both common and systematic names for complex substituents
• Systematic names are crucial for more than 4 carbons

Additional Resources

• Study guides and practice problems available on Chad's Prep website