Chemical Properties Of Pyrrole

Chemical properties of pyrroleyrrole and its methyl substituted homologues are present in bone tar. Colorless liquid. The boiling point is 130 ~ 131℃, the relative density is 0.9691 (20/4℃). Slightly soluble in water, soluble in ethanol, ether and other organic solvents. Pyrrole can become black under the action of trace oxygen; Loose plate reaction gives red; Polymerized to pyrrole red under the action of hydrochloric acid; The oxidizer is generally unstable. It can undergo substitution reactions, mainly at 2 or 5 positions. At 15℃, pyrrole is nitrated with nitric acid in acetic anhydride to obtain 2-nitropyrrole, the yield is not high, and part of it becomes a resinous substance. Pyrrole is formally a secondary amine, but it dissolves slowly in dilute acids; The hydrogen in the ring is replaced by an alkyl group, which increases the alkalinity and forms an insoluble salt. Pyrrole can form salt with picric acid; It can also be reduced to dihydrogen and tetrahydropyrrole.
Pyrrole can be prepared by the reaction of 1, 4-dicarbonyl compounds with ammonia. Commercially, pyrrole is prepared by the catalytic reaction of butylenediol with ammonia. The compound of pyrrole in parallel with benzene is called indole and is an important compound. Some pyrrole derivatives have important physiological functions, for example, chlorophyll, heme are derivatives of the porphyrin ring system formed by four pyrrole rings. Tetrahydropyrrole is an important reagent that reacts with ketones to form enamine, which has a carbon-carbon double bond para-amino. For example, enamines formed by cyclohexanone and tetrahydropyrrole have many uses in organic synthesis. In general, before experiments with pyrrole as a raw material, it is necessary to re-distillation before use, because pyrrole is easily polymerized to form polypyrrole (black solid) when exposed to air for a long time.
Acid comparison: acetic acid > phenol > pyrrole > cyclohexanol