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acetylene

Product name acetylene
Synonyms ethyne
ethine
GOST no data
CAS 74-86-2

Acetylene is a colorless, flammable, odorless gas. The characteristic garlic-like odor of technical grade acetylene is attributable to contamination by impurities (phosphine, arsine). Acetylene is boundedly soluble in water, ethanol, benzene, acetic acid. Readily soluble in acetone, dimethylformamide (DMF). Acetylene has a linear geometry, all four atoms are placed in the same straight line. It is a simplest alkyne and most reactions occur at its triple bond. Addition occurs in two stages. At the first step ethylene devivatives formation take place and then reaction tesults in ethane derivatives:

HCCH + Cl2 --> ClHC=CHCl
ClHC=CHCl + Cl2 --> Cl2HC-CHCl2


Acetylene can be hydrogenated in the presence of nickel or platinum catalyst to give ethylene and then ethane respectively. It reacts with water in the presence of mercury(II) salts resulting in acetaldehyde formation (Kucherov reaction). Interaction with hydrogen cyanide in acid medium yields to acrylonitrile:

HCCH + H2O --> H3C-CHO
HCCH + HCN --> H2C=CH-CN


Acetylene is a raw material in lewisite synthesis. It is readily reacts with formaldehyde on C-H bond (Reppe synthesis); able to substitute hydrogen atom with metal to form metal acetylenides MCCH. Interaction of acetylene with organomagnegium compounds results in acetylene magnesium halides (Iotsich reaction)

Acetylene gas is highly unstable, and can explode with extreme violence if the pressure of the gas exceeds about 0.2MPa or the temperature is above 500C. Because of it is shipped and stored dissolved in acetone or dimethylformamide (DMF), contained in a metal cylinder with porous filling (e.g. active carbon), which renders it safe to transport and use.

Production.

Acetylene is synthesized:

  • by thermooxidative methane cracking:

    6CH4 + 4O2 --> HCCH + 8H2 + 3CO + CO2 + 3H2O

  • by electrocracking of methane in arc furnace:

    2CH4 --> HCCH + 3H2

  • by fusion of calcium carbonate with coke at the temperature ~2000C followed by calcium carbide hydratation to release acetylene:

    CaCO3 + 3C --> CaC2 + CO + CO2
    CaC2 + 2H2O --> HCCH + Ca(OH)2


  • by natural gas pyrolysis at 1500C;

    Uses.

    Most of the acetylene produced is used in chemical synthesis.

  • in making chlorinated hydrocarbons, such as tetrachloroethylene, trichloroethylene, vinyl chloride and many others;
  • as an intermediate in manufacturing acetaldehyde, acetic acid, acetone, ethanol and others;
  • for preparation of acrylonitrile, vinyl alcohols, vinyl acetate;
  • in 1,4-butylene glycol and hydroquinone production;
  • for oxyacetylene gas welding and cutting;
  • for carburization of steel;

  • Manufacturer(s) no data
    Chemical structure of acetylene

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