A nitrogenous heterocyclic base found in coal tar, bone oil, and other distillates of organic substances, and also produced synthetically as a colorless liquid, C4H5N, having on odor like that of chloroform. It is the nucleus and origin of a large number of derivatives. So called because it colors a splinter of wood moistened with hydrochloric acid a deep red.

a five-membered aromatic ring, containing four carbon atoms and one nitrogen

A colourless liquid that provides the building blocks for a large number of vital compounds such as haemoglobin, chlorophyll and bile acids.

a basic chemical structure that is used in the formation of heme, which makes blood red