Heterocyclic Compounds are organic compounds with ring structures containing at least one heteroatom like nitrogen, oxygen, or sulfur.
- A heterocyclic compound is a cyclic compound that contains atoms of at least two different elements in its ring structure.
- Typically, these rings are made of carbon atoms and at least one heteroatom, such as:
- Nitrogen (N)
- Oxygen (O)
- Sulfur (S)
- Heterocyclic compounds can be aromatic or non-aromatic, and they may contain single rings or multiple fused rings.

Applications of Heterocyclic Compounds
- Pharmaceuticals: Many drugs contain heterocyclic rings, including antibiotics (e.g., penicillin), antivirals, and anticancer agents.
- Biological molecules: Nucleic acids (DNA/RNA bases), vitamins (B1, B6), alkaloids.
- Agrochemicals: Herbicides, fungicides, and insecticides.
- Materials science: Organic semiconductors, dyes, and polymers.
Examples of Common Heterocyclic Compounds
| Name | Structure Type | Notes |
| Pyridine | 6-membered, 1 N | Analogous to benzene with 1 nitrogen |
| Pyrrole | 5-membered, 1 N | Found in porphyrins and heme |
| Furan | 5-membered, 1 O | Aromatic but more reactive than benzene |
| Thiophene | 5-membered, 1 S | Aromatic, used in conductive materials |
| Imidazole | 5-membered, 2 N | Found in histidine and enzymes |
| Indole | Benzene + pyrrole | Present in tryptophan, serotonin |
| Thiazole | 5-membered, S and N | Found in vitamin B1 (thiamine) |
| Purine | Double-ring, 4 N | Base of DNA (adenine, guanine) |