What is "pyrrole"

pyrrol \pyr"rol\, pyrrole \pyr"role\, n. [Gr. ? flame-colored (from ? fire) + L. oleum oil.] (Chem.) 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.

n. (context organic chemistry English) Any of a class of aromatic heterocyclic compounds containing a ring of four carbon atoms and a nitrogen atom; especially the simplest one, C₄H₅N. (from 19th c.)

Pyrrole is a heterocyclic aromatic organic compound, a five-membered ring with the formula C H NH. It is a colorless volatile liquid that darkens readily upon exposure to air. Substituted derivatives are also called pyrroles, e.g., N-methylpyrrole, CHNCH. Porphobilinogen, a trisubstituted pyrrole, is the biosynthetic precursor to many natural products such as heme.

Pyrroles are components of more complex macrocycles, including the porphyrins of heme, the chlorins, bacteriochlorins, chlorophyll, and porphyrinogens.