Introduction to IUPAC Naming in Chemistry

Jan 7, 2025

Crash Course Organic Chemistry: Introduction to IUPAC Naming

Key Points

  • Language and Chemistry:
    • Chemistry has its own complex language, similar to regional language variations.
    • Miscommunication can occur when common names are used instead of standard names.
    • The International Union of Pure and Applied Chemistry (IUPAC) standardizes chemical nomenclature to allow accurate communication among chemists globally.

IUPAC Naming System

  • Purpose:
    • To create a universally understood chemical naming system.
  • Common vs. Systematic Names:
    • Common names are based on source, smell, or color (e.g., vanillin from vanilla beans).
    • Systematic names follow IUPAC rules and provide structure information.

Steps in IUPAC Naming

  1. Find the Longest Carbon Chain:
    • Identify and name the longest carbon chain, forming the root name.
    • Mnemonic: "Monkeys eat purple bananas" (meth, eth, prop, but).
  2. Identify the Highest Priority Functional Group:
    • Add its suffix to the root name.
  3. Identify Substituents and Their Positions:
    • Add a numbered prefix to the root name.

Specifics of Hydrocarbons

  • Alkanes:
    • Single bonds, suffix -ane (e.g., hexane).
    • Low energy, few reactions compared to other hydrocarbons.
  • Alkenes:
    • Double bonds, suffix -ene (e.g., pent-1-ene).
    • Number carbons starting nearest to the double bond.
  • Alkynes:
    • Triple bonds, suffix -yne (e.g., oct-4-yne).

Naming Substituents

  • Substituents on Alkanes:
    • Prioritize numbering to get the lowest possible numbers.
    • Use prefixes like methyl, ethyl with numbered positions (e.g., 2-methylhexane).
    • Use di-, tri-, tetra- for multiple substituents of the same kind.
    • Halogen substituents: chloro, bromo, iodo.
  • Substituents on Alkenes and Alkynes:
    • Prioritize double/triple bonds over substituents for numbering.
    • Alphabetical order for substituent prefixes (ignoring multipliers).

Complex Naming Examples

  • Example molecule: 4-bromo-3-methyl-hep-1-ene-6-yne.
  • Example of dichloromethane vs methylene chloride, illustrating common vs systematic names.

Conclusion

  • Understanding systematic naming involves root names, suffixes for functional groups, and prefixes for substituents.
  • Next lessons will cover systematic naming with heteroatoms.