Preparation and Reactions of Pyrrole

Preparation and Reactions of Pyrrole

Preparations and Reactions of Pyrrole

Preparation of Pyrrole

Preparation of Pyrrole from Acetylene

By passing a mixture of acetylene and ammonia through a red hot tube, pyrrole is obtained.
Preparation of Pyrrole from Acetylene

Preparation of Pyrrole from Succinamide

Pyrrole is obtained when succinamide is heated with zinc dust.
Preparation of Pyrrole from Succinamide

Preparation of Pyrrole from Furan (Commercial Method)

When mixture of furan, ammonia and steam is passes over aluminium oxide catalyst at 480-500° C, pyrrole is obtained.
Preparation of Pyrrole from Furan (Commercial Method)

Preparation of Pyrrole from Succinic dialdehyde

When succinic dialdehyde heated with ammonia, pyrrole is obtained.
Preparation of Pyrrole from Succinic dialdehyde

Physical Properties of Pyrrole

Pyrrole is a colorless liquid, Boiling Point is 131° C, Readily turns into brown color on air exposure, Sparingly soluble in water but dissolve in ethanol and ether. Its odour is similiar to chloroform.

Chemical Properties of Pyrrole/Reactions of Pyrrole

Resonance of Pyrrole

Resonance of Pyrrole

Basic Character of Pyrrole

Pyrrole is a weak base. It reacts with dilute hydrochloric acid to give a crystalline hydrochloride. The lone pair of electron on nitrogen involved in the formation of the delocalized π-molecular orbital and not available for the formation of a new bond with proton. If a proton is added to the nitrogen atom by reaction with an acid, the resulting structure losses their aromaticity and the resonance energy is lost. This makes pyrrol cation very unstable in comparision to the free pyrrole and shows why pyrrole is very weak base.
Electrophylic Substitution Reactions of Pyrrole

Acidic Character of Pyrrole

Pyrrole is a very weak acid. This is shown by its reaction with solid KOH. The acidic character of pyrrole is due to the electron pair of nitrogen delocalized and makes it positively charged and increases the possibility of proton abstraction giving pyrrole anion. Pyrrole anion is stabilized by delocalization of negatively charged over the ring.
Electrophylic Substitution Reactions of Pyrrole

Electrophylic Substitution Reactions

Pyrrole undergoes electrophylic substitution reactions at carbon-2 and gives 2-substituted product however, at carbon-3 gives 3-substituted product which is less stable as only two resonating structures are possible. Electrophylic Substitution Reactions of Pyrrole

Nitration of Pyrrole

Pyrrole is nitrated by cold solution of nitric acid in acetic anhydride to give 2-nitropyrrole.
Nitration of Pyrrole

Sulphonation of Pyrrole

Pyrrole is sulphonated with sulphur trioxide in pyridine at about 100°C to yield pyrrole-2-sulphonic acid.
Sulphonation of Pyrrole

Halogenation of Pyrrole

Chlorination is carried out with sulphuryl chloride in ether at 0°C.
Bromination with bromine in ethanol at 0°C.
Iodination with iodine in an aqueous solution of potassium iodide.
All these halogenation gives tetrahalogen pyrrole.
Halogenation of Pyrrole

Friedel-Craft Acylation of Pyrrole

Pyrrole is acetylated with acetic anhydride at 250°C to give 2-acetylpyrrole.
Friedel-Craft Acylation of Pyrrole

Kolbe-Schmitt Carboxylation of Pyrrole

Pyrrole reacts with aqueous potassium carbonate at 100°C to give pyrrole-2-carboxylic acid.
Kolbe-Schmitt Carboxylation of Pyrrole

Reimer-Tiemann Reaction of Pyrrole

Pyrrole reacts with chloroform in the presence of alkali to yield 2-formyl pyrrole (pyrrole 2-aldehyde) and 3-chloropyridine.
Reimer-Tiemann Reaction of Pyrrole

Diazo-Coupling of Pyrrole

Pyrrol couples with benzenediazoniumchloride in a weakly acidic solution to give 2-phenylazopyrrole.
Diazo-Coupling of Pyrrole

Oxidation of Pyrrole

Pyrrole is oxidized to maleic imide by chromium trioxide in acetic acid.
Oxidation of Pyrrole

Reduction of Pyrrole

Zn/AcOH reduce pyrrole to 3-pyroline (
i.e. 2,5-dihydropyrrole) while catalytic reduction completely hydrogenates the ring system to form pyrrolidine.
Reduction of Pyrrole

Ring-Expansion of Pyrrole

Pyridine obtained when pyrrole is treated with sodium methoxide and methelene iodide.
Ring-Expansion of Pyrrole

Ring Opening of Pyrrole

When pyrrole is treated with hot ethanolic hydroxylamine, pyrrole ring opens to form dioxime of succindialdehyde.
Ring Opening of Pyrrole

Preparation and Reactions of Furan

Preparation and Reactions of Thiophene