The Pyrrole reference article from the English Wikipedia on 24-Apr-2004
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Pyrrole

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In organic chemistry, a pyrrole is a five membered aromatic ring, 4 elements of which are carbon atoms, one element of which is a nitrogen atom. The molecular formula for a pyrrole is C4NH5. The structure is:

Image:pyrrole.png

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.