Any of a class of aromatic compound s with a six-member aromatic ring composed of five carbon atoms and one nitrogen atom, making it a heterocyclic compound .
The simplest one is pyridine itself (C 5 H 5 N). Natural compounds with pyridine rings include niacin and pyridoxine (see vitamin B complex ), the nicotine ). Pyridine is used as a raw material for various drugs, vitamins, and fungicides and as a solvent. Because it has a nauseating odour and a burning taste, it is added to ethanol and antifreezes to make them undrinkable (see denaturation ).