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pyridine

Product name pyridine
Synonyms azabenzene
azine
GOST no data
CAS 110-86-1

Pyridine is a clear, colorless, flammable liquid with a characteristic, sour, putrid odor. It is a heterocyclic aromatic organic compound. It is fully miscible in water, ethyl alcohol, benzene and most organic solvents. Pyridine forms azeotrope with water (58% wt of pyridine, bp 94°C).

It is a basic compound, its basicity is less than basicity of tertiary alkyl amines due to influence of aromatic ring pi-system. But nevertheless an equatorial lone pair of electrons at the nitrogen atom of pyridine does not participate in the aromatic pi-system. As a basic compound, pyridine reacts with inorganic acids to form stable salts; interaction with alkyl halides result in pyridinium salts. Pyridine is able to form complexes with Lewis acids: SO2, SO3, Br2, H2O. Due to lone pair of electrons it can act as a neutral ligand in a metal coordination sphere.

Nucleophilic substitution in 2 and 4-positions in pyridine occures at much more soft conditions than in benzene, but electrophilic substitution occurs at hard high temperature and with a low yields. Pyridine is relatively stable to oxidizers action, but interaction with peracids results in pyridine N-oxide. Pyridine is a good solvent, it is able to dissolve inorganic salts, such as AgBr, Hg2Cl2 and others. It is a harmful substance if inhaled, ingested or absorbed through skin, it is known to reduce male fertility and is considered carcinogenic as well. Common symptoms of exposure include: headache, coughing, asthmatic breathing, laryngitis, nausea and vomiting.

Production.

  • from crude coal tar (contains up to 0.08% of pyridine);
  • by pyrolysis of wood, peat or bones;
  • by the reaction of butadiene with hydrogen cyanide in the presence of aluminium oxide Al2O3:

    CH2=CHCH=CH2 + HCN --> C5H5N

  • by the reaction of acetylene with hydrogen cyanide. Process is catalyzed with mercury(II) chloride HgCl2:

    2HCCH + HCN --> C5H5N

  • by thermal cyclocondensation of acetaldehyde, formaldehyde and ammonia at 200-250°C at high pressure on zeolite catalyst (Chichibabin reaction):

    2CH3CHO + CH2O + NH3 --> C5H5N

    Uses.

  • as a solvent and reaction medium in laboratory synthesis and in chemical industry;
  • as a raw material and an intermediate in making insecticides, herbicides, fungicides, dyes, paints, rubber chemicals, adhesives, explosives and disinfectants;
  • for preparation of pharmaceuticals and food flavorings;
  • as a denaturant for technical ethyl alcohol, antifreeze mixtures;
  • as a dyeing assistant;

  • Manufacturer(s) Dzerzhinsk phenol plant
    Chemical structure of pyridine

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