Lecture Notes: Organic Chemistry - IUPAC Nomenclature

Introduction

• Topic: IUPAC Nomenclature of Organic Compounds
• Purpose of Nomenclature:
  • Identification of compounds
  • Avoid confusion from using scientists' names
  • Consistent naming globally

Why Names?

• Names help in identifying and studying compounds.
• 5 million known organic compounds; 30,000 new compounds discovered annually.
• Scientist names for compounds impractical due to large numbers and potential duplication.

IUPAC Nomenclature

• IUPAC: International Union of Pure and Applied Chemistry
• Develops rules for naming organic compounds
• Ensures each compound has a unique, standardized name globally

Naming Structure

• Parts of an Organic Name:
  • Prefix: First name (branches/substituents)
  • Word Root: Middle name (number of carbon atoms in the chain)
  • Suffix: Last name (functional groups and types of bonds)

Suffix Types

• Primary Suffix: Indicates types of bonds (ane, ene, yne)
• Secondary Suffix: Indicates functional groups (discussed in future lectures)

Common vs IUPAC Names

• Common Names:
  • Derived from source or nature
  • Example: Acetic acid (CH3COOH) known as ethanoic acid in IUPAC
• IUPAC Names:
  • Official, globally recognized

Rules for Naming

Rule 1: Longest Chain Selection

• Select the longest continuous carbon chain as the main structure.

Rule 2: Numbering the Chain

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

Rule 3: Writing the Name

• Format: Number - Substituent - Word Root - Primary Suffix

Rule 4: Lowest Locant Rule

• When multiple substituents, number to give the lowest sum to substituents.

Rule 5: Alphabetical Order

• List substituents in alphabetical order when naming.

Rule 6: Use of Di-, Tri-, Tetra-

• Use these prefixes for multiple identical substituents.

Rule 7: Maximum Branches

• If two chains of equal length, choose the one with more branches.

Examples

• Practical examples demonstrating the rules.
• Explained how to consider complex branches and convert bond-line diagrams into regular structures.

Conclusion

• Mastery of these rules allows naming of any saturated hydrocarbons, even with complex branches.
• Additional videos will cover naming unsaturated hydrocarbons and those with functional groups.

Homework

• Practice naming provided examples and submit answers for review.