IUPAC Nomenclature: Rules and Examples

Aug 4, 2024

IUPAC Nomenclature Lecture Notes

Introduction

  • Full name of IUPAC: International Union of Pure and Applied Chemistry
  • Need for IUPAC: To bring uniformity in the naming of organic compounds, facilitating global communication

Importance of IUPAC Nomenclature

  • Establish international standards
  • Eliminate confusion caused by different names for the same compound
  • Simplify global communication

Rules of IUPAC Nomenclature

Three Main Parts

  1. Word Root: Number indicating the main carbon chain
  2. Prefix: Substituents attached before the main chain
  3. Suffix: Type of bonds or functional groups

Key Components

  • Word Root: Number of carbons in the main chain

    • 1: Meth
    • 2: Eth
    • 3: Prop
    • 4: But
    • 5: Pent
    • 6: Hex
    • 7: Hept
    • 8: Oct
    • 9: Non
    • 10: Dec

  • Suffix:

    • Single Bond: -ane
    • Double Bond: -ene
    • Triple Bond: -yne

  • Functional Groups:

    • OH: Alcohol (-ol)
    • COOH: Carboxylic Acid (-oic acid)
    • CHO: Aldehyde (-al)
    • C=O: Ketone (-one)
    • COOR: Ester (alkyl alkanoate)
    • Ether: (alkoxyalkane)

Steps in Naming

  1. Longest Chain Selection: Select the longest carbon chain
  2. Numbering: Number the chain from the direction that gives the least number to the substituents
  3. Substituents: List substituents in alphabetical order

Understanding through Examples

  • Example 1: 3-Methylpentane

    • Longest chain: 5 carbons (Pentane)
    • Substituent: Methyl at 3rd position (3-Methyl)
    • Final Name: 3-Methylpentane

  • Example 2: 4-Bromo-3-Ethyl-2-Methylhexane

    • Longest chain: 6 carbons (Hexane)
    • Substituents: Bromo at 2nd, Ethyl at 3rd, Methyl at 4th positions
    • Alphabetical Order: Bromo, Ethyl, Methyl
    • Final Name: 4-Bromo-3-Ethyl-2-Methylhexane

Complex Substituents

  • Follow numbering and IUPAC rules for complex substituents as well
  • Branching can occur within substituents
    • Example: 4-(1,2-Dimethylpropyl)nonane
      • Longest chain: 9 carbons (Nonane)
      • Substituent: 1,2-Dimethylpropyl at 4th position
      • Final Name: 4-(1,2-Dimethylpropyl)nonane

Bond Line Notation

  • Use of Bond Line Notation
  • Do not explicitly show carbons; identify carbons by bends and ends
  • Example: CH3-CH2-CH=CH-CH3

Conclusion

  • IUPAC Nomenclature brings standardization to the naming of organic compounds
  • By following various rules and steps, even complex naming is possible
  • More videos will be released to explain this topic in greater depth