Pyridine

Synonyms:

azabenzene, azine

Chemical formula:

C5H5N

International name:

PYRIDINE

Grade:

Import

Appearance:

Colorless liquid

PYRIDINE is a colorless liquid with a specific odor; it is miscible in all ratios with water and majority of organic solvents; with water forms azeotropic mixture.

Pyridine is a heterocyclic compound, weak base; it forms salts with acids and salts of N-alkylpyridinium C5H5N•RX with halogenalkyls (RX) as well as with complex compounds FeCI2, SO2, SO3, Br2, H2O. Pyridine is toxic, threshold limit value of vapors in the air is 0.0015 mg/l.

Production:

The main source of pyridine is coal tar pitch in which its concentration is about 0.08%. Pyridine is produced as follows:

• from coal tar pitch;
• from products of wood, turf or bone pyrolysis;
• by a reaction of butadiene with hydrogen cyanide in the presence of aluminium oxide Al2O3:
• CH2=CHCH=CH2 + HCN —> C5H5N
• by a reaction of acetylene with hydrogen cyanide. The process is catalyzed by mercury chloride (II):
• 2HCCH + HCN —> C5H5N
• by a reaction of acetaldehyde, formaldehyde and ammonia thermal cyclocondensation at 200-250°C at high pressure using a ceolite catalyst (Chichibabin reaction): 2CH3CHO + CH2O + NH3 —> C5H5N

Application:

Pyridine is widely used in industry in organic synthesis.

• as a solvent and reagent in synthetic organic chemistry and in industry;
• as a stock compound and intermediate in production of insecticides, herbicides, fungicides, dyers, rubber additives, adhesives, explosive substances, disinfecting agents;
• in synthesis of pharmaceutical preparations, food odorants;
• as a denaturant to technical ethyl alcohol, antifreezes;
• as an auxiliary material during fabric dyeing, etc.

Pyridine derivatives, e.g. 2-methyl-5-vinylpyridine, are used in production of vinylpyridine rubbers. Pyridine sulfotrioxide C5H5N•SO3 is a soft sulphonating agent.