Pyrrole

PYRROLE, a 5-membered heterocycle. The products of the addition of two hydrogen atoms to pyrrole are called pyrrolines, and the addition of four hydrogen atoms are called pyrrolidines. Pyrrole is a colorless liquid,

with an odor resembling chloroform; boiling point 130–131°, specific gravity d²=0.96694, soluble in alcohol and ether; it is easily oxidized, difficult to nitrate and sulfonate; it is a weak base; under the action of acids, it splits off part of the nitrogen in the form of NH₃ and polymerizes into so-called "red pyrrole." Pyrrole resembles phenol in a number of properties. A pine splinter, moistened with HCl and dried, gives a red coloration with a solution of pyrrole or its homologs. It is obtained synthetically by the dry distillation of ammonium mucate.

Pyrrole is contained in bone oil, which is obtained during the dry distillation of proteins, and in small quantities in coal tar. As a nucleus included in the composition of plant (chlorophyll) and animal pigments (hemoglobin, bile), it is of great biological interest. The presence of pyrrole establishes a close connection between individual representatives of plant and animal pigments. It is obtained upon the cleavage of melanins (see). Upon the reduction of phylloporphyrin, hematoporphyrin, heme, and bilirubin with hydriodic acid, a mixture of homologs of pyrrole and pyrrolecarboxylic acids is obtained (see also Porphyrin). Derivatives of pyrrolidine include pyrrolidine- and hydroxypyrrolidine-carboxylic acids, which are part of the protein molecule. Certain alkaloids are also derivatives of pyrrolidine: hygrine, stachydrine, nicotine, atropine, cocaine. The introduction of pyrrole to a dog or rabbit causes the appearance of methylpiperidine in the urine. PYRROLBLAU. A derivative of isatin, an acid dye, easily soluble in water and alcohol. It is used in histological technique as a vital stain for detecting cells of the macrophage type (pyrrole cells) in connective tissue. However, it is preferable to use isamine blue or trypan blue for this purpose.