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Nomenclature of Organic Compounds

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Topics

  • Common Naming System
  • IUPAC Nomenclature

Common Naming System

Initially, carbon compounds were named based on their source, discovery, or physical properties.  These names were not systematic but widely used.

Examples: methane, ethane, propane, and butane.

Need for a Systematic Approach:

  • As the number of known carbon compounds increased, a consistent and structured system was needed.
  • Later alkanes were named based on the number of carbon atoms in the chain. This helped in classifying compounds more efficiently.

Isomer Naming and Differentiation:

  • Some compounds with the same molecular formula but different structures were discovered. These structural variations, called isomers, required distinct names.
  • Example: n-Butane (straight-chain) and iso-Butane (branched-chain), both formulated as C₄H₁₀, but different structures and properties.
  • Thus, while common names were initially used, the need for a systematic and globally accepted nomenclature led to the development of structured naming conventions.

IUPAC Nomenclature

IUPAC provides a standardised naming system for organic and inorganic compounds to ensure global consistency and avoid confusion.

Key Components:

  1. Substituents: Functional groups attached to the main carbon chain.
  2. Parent Chain: The longest continuous carbon chain in the molecule.
  3. Chemical Ending: Represents the functional group type (e.g., -ol for alcohol, -al for aldehyde).

Methods for Modifying the Root Name:

  • Substitutive: The highest-priority functional group modifies the suffix, while other groups act as prefixes.
  • Functional Group-Based: Named according to the most significant functional group (e.g., ketones, alcohols).
  • Replacement: When a carbon atom is replaced by another atom.
  • Conjunctive: Combines different named subunits.
  • Trivial Naming: Some widely used compounds retain their common (trivial) names under IUPAC rules.
This systematic approach ensures that chemical names are clear, uniform, and internationally recognised.
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Video Tutorials

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Shaalaa.com | Carbon and Compounds part 15 (Why name hydrocarbon)Carbon & Compounds part 15 (Why name hydrocarbon)

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Carbon and Compounds part 15 (Why name hydrocarbon)Carbon & Compounds part 15 (Why name hydrocarbon) [00:10:35]
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