Acetylene

The acetylene (called éthyne by the nomenclature IUPAC) is a chemical Composé Hydrocarbure of the class of the Alcyne S of rough Formule C 2 H 2. He was discovered by Edmund Davy in England in 1836. It is the simplest alkyne compound, made up of two atoms of Carbone and two of Hydrogène. The two carbon atoms are connected by a Triple connection which contains the majority of its chemical energy.

Its structure is linear:

Berthelot, in 1862, was the first to synthesize acetylene by an electric arch produced between two electrode of Graphite bathing in an atmosphere of Hydrogène:

2 C + H2 → C2H2

Acetylene is a colorless Gaz, with the odor of garlic, extremely Inflammable at temperature and standard pressure and which is liquefied at a temperature of -83 ºC and is solidified with -85 ºC. It can in a free state break up quickly when the pressure is higher than 100 kPa, for this reason it is stored dissolved in the Acétone or the diméthylformamide (DMF), them same included in a stabilizing porous matter.

Chemistry

The chemical properties of acetylene are explained mainly by the presence in its molecule of triple connection resulting from the superposition of a connection simple S (coming from the fusion of two Orbitale S sp) and of two connections p resulting from the orbital fusion of two 2p. This connection, length 0,124 Nm and characterized by an energy of 811 kJ, is thus less stable than the connections simple (614 kJ) and doubles (347,3 kJ), and consequently more reactive.

Obtaining

Acetylene does not exist in nature. However, the synthesis of Berthelot revolutionized the designs of the time because for the first time a substance organic (and nonmineral) was synthesized by the man, without the intervention of a " fluid vital " divin.
The principal industrial methods to produce acetylene are:

Carbochimic method

One uses as raw material the calcareous and coke or of the charcoal. In a furnace at high temperature (1700 minimum ºC) heated by an electric current passing in the reactional medium in fusion, it occurs Carbure of calcium according to the reactions:

CaCO3 → CAD + CO2

CAD + 3 C + 108.300 calories → CaC2 + CO

In the user, the carbide reacts with water to produce acetylene.

CaC2 + 2:00 2O → C2H2 + Ca (OH) 2 + 31.000 calories

Combustion partial of methane

Combustion partial of the Méthane produces also acetylene:

3 CH 4 + 3 O2 → C2H2 + CO + 5:00 2O

Dehydrogenation of alkanes

The heaviest alkanes of oil and natural gas are cracked in lighter molecules which are dehydrogenated at high temperature.

C2H6 → C2H2 + 2:00 2

Applications

Applications of acetylene:

  • the strong percentage of carbon gives a very lighting flame used for example in the lamps used in the careers.

  • the high heat of combustion (3810°C in pure oxygen) of acetylene makes it possible to use it for the welding. Only the flame resulting from acetylene is reducing and is adapted to the welding. It allows the varied metal assembly (steels, stainless, alloys of copper, but also under certain conditions the aluminum alloyed with silicon.

  • the reaction of acetylene with the Hydrochloric acid is a manner of producing Chlorure of vinyl (monomeric of the Chloride polyvinyl).

Reactions of acetylene

  • acetylene and the monoalquilacetylenes are the only hydrocarbons which have a hydrogen being acid and which can be exchanged by a metal.

Certain acétylénures as are explosives with the shock.

  • acetylene gives the Benzène by Polymérisation under the action of heat.

  • By Dimérisation in the presence of catalysts, one obtains vinylacetylene to which one adds Chlorure of hydrogen to obtain chloroprene, Monomère polychloroprene or Néoprène.

See too

Simple: Acetylene

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