Pyrrole
Pyrrole, or
pyrrol, is a
heterocyclic aromatic organic compound, a five-membered ring with the
formula C4H5N.
Pyrroles are components of larger aromatic rings, including the
porphyrins of
heme, the
chlorins and
bacteriochlorins of
chlorophyll, and the
corrin ring of
vitamin B12.
Pyrrole has very low basicity compared to
amines and other aromatic compounds like
pyridine where the ring
nitrogen is not bonded to a
hydrogen atom. This is because the
lone pair of
electrons of the nitrogen atom becomes delocalized in the aromatic ring.
Pyrrole undergoes electrophillic substitution predominantly at the 2 and 5 positions, though the substitution product at positions 3 and 4 is obtained in low yields. Pyrrole compounds can also participate in cycloaddition (
Diels-Alder) reactions under certain conditions, such as Lewis acid catalysis, heating, or high pressure.
In a 1994 report released by five top cigarette companies, pyrrole is one of the 599 additives to cigarettes. Its use or purpose, however, is unknown, like most
cigarette additives.[
1]
*
Polypyrrole*
Indole, a derivative with a fused
benzene ring.
*
Thiophene, an analog with a
sulfur instead of the
nitrogen atom.
*
Furan, an analog with an
oxygen instead of the nitrogen.
*
Phosphole, a non-aromatic
phosphorus analog.
*
Arsole, a non-aromatic
arsenic analog.
*
Pyrrolidine, the saturated hydrogenated derivative
*
Simple aromatic rings
*
Pyroluria*
General Synthesis and Reactivity of Pyrrole*
Synthesis of pyrroles (overview of recent methods)*
Substitution reaction mechanisms of nitrogen-containing heteroaromatics#
