Phosgene

Phosgene (also known as carbonyl chloride, COCl2) is a highly toxic gas or refrigerated liquid that was used as a chemical weapon in World War I. It has no color, but is detectable in air by its odor, which resembles moldy hay.

Production and use

Industrially, phosgene is produced by passing purified carbon monoxide and chlorine gas through a bed of highly porous carbon, which acts as a catalyst.

Related Topics:
Carbon monoxide - Chlorine - Carbon - Catalyst

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The chemical equation for their reaction is

Related Topics:
Chemical equation - Reaction

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:CO + Cl2 → COCl2

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The reaction is exothermic, so the reactor must be continually cooled to carry away the heat it produces.

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Typically, the reaction is carried out between 50°C and 150°C.

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Above 200°C, phosgene decomposes back into carbon monoxide and chlorine.

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Because of the safety issues with storing and transporting it, phosgene is almost always produced and consumed within the same chemical plant. It is listed on schedule 3 of the Chemical Weapons Convention: all production sites must be declared to the OPCW.

Related Topics:
Schedule 3 - Chemical Weapons Convention - OPCW

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Phosgene is used chiefly in the production of polymers including polyurethanes, polycarbonates, and polyureas.

Related Topics:
Polymer - Polyurethane - Polycarbonate - Polyurea

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It is also used to produce isocyanates and acid chlorides as intermediates in the dye, pesticide, and pharmaceutical industries.

Related Topics:
Isocyanate - Acid chloride - Dye - Pesticide - Pharmaceutical

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It is possible to use phosgene to isolate certain metals including aluminium and uranium from their ores, but these methods are not widely used.

Related Topics:
Metal - Aluminium - Uranium - Ore

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In the laboratory, the use of the gaseous phosgene has long since been replaced by diphosgene, which is a liquid at room temperature, or triphosgene, a crystalline substance.

Related Topics:
Diphosgene - Triphosgene

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