Nomenclature of Heterocyclic Compounds

Nomenclature of Heterocyclic Compounds follows IUPAC rules, naming based on ring size, heteroatom type, and saturation or unsaturation.

Heterocycles are named using common (trivial) names or systematic IUPAC names.

1. Common/Trivial Names

   • These are historical or widely accepted names, commonly used for simple or well-known heterocycles.
   • Examples:
     • Aziridine (3-membered ring with N)
     • Oxirane (epoxide, 3-membered ring with O)
     • Pyrrole (5-membered, aromatic, with N)
     • Furan (5-membered, aromatic, with O)
     • Thiophene (5-membered, aromatic, with S)
     • Pyridine (6-membered, aromatic, with N)

2. IUPAC Nomenclature

   • The IUPAC system uses standardized prefixes and suffixes:

Prefixes for Heteroatoms:

Suffixes Based on Ring Size and Saturation:

Naming Rules:

• Identify the ring size and saturation.
• Assign prefixes based on the type and position of heteroatoms.
• Choose the appropriate suffix.
• Number the ring to give the heteroatoms the lowest possible locants.
• In complex cases, consider the principal ring and use fusion nomenclature for attached rings.

Examples:

1. 1. Imidazole
      • 5-membered aromatic ring
      • Contains two nitrogen atoms
      • Common and IUPAC-accepted name
   2. Morpholine
      • 6-membered saturated ring
      • Contains one oxygen and one nitrogen
      • IUPAC name: 1-oxa-4-azacyclohexane
      • Common name: Morpholine
   3. Indole
      • Fused bicyclic compound: benzene + pyrrole
      • IUPAC name: 1H-indole

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