Diphosgene is an organic

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula ClCO₂CCl₃. This colorless liquid is a valuable reagent in the

synthesis Synthesis or synthesize may refer to: Science Chemistry and biochemistry *Chemical synthesis, the execution of chemical reactions to form a more complex molecule from chemical precursors **Organic synthesis, the chemical synthesis of organi ...

of organic compounds. Diphosgene is related to

phosgene Phosgene is an organic chemical compound with the formula . It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. It can be thought of chemically as the double acyl chloride analog of ...

and has comparable

toxic Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacterium, or plant, as well as the effect on a subst ...

ity, but is more conveniently handled because it is a liquid, whereas phosgene is a gas.

Production and uses

Diphosgene is prepared by radical chlorination of methyl chloroformate under UV light: :Cl-CO-OCH₃ + 3 Cl₂ —(hv)→ Cl-CO-OCCl₃ + 3 HCl Another method is the radical chlorination of methyl formate: :H-CO-OCH₃ + 4 Cl₂ —(hv)→ Cl-CO-OCCl₃ + 4 HCl Diphosgene converts to phosgene upon heating or upon

catalysis Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

with

charcoal Charcoal is a lightweight black carbon residue produced by strongly heating wood (or other animal and plant materials) in minimal oxygen to remove all water and volatile constituents. In the traditional version of this pyrolysis process, ca ...

. It is thus useful for reactions traditionally relying on phosgene. For example, it convert

amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...

s into

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

s, secondary amines into carbamoyl chlorides,

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an Substituent, R-group. The general formula of a carboxylic acid is often written as or , sometimes as with R referring to an organyl ...

s into

acid chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

s, and

formamide Formamide is an amide derived from formic acid. It is a colorless liquid which is miscible with water and has an ammonia-like odor. It is chemical feedstock for the manufacture of sulfa drugs and other pharmaceuticals, herbicides and pesticides, ...

s into

isocyanide An isocyanide (also called isonitrile or carbylamine) is an organic compound with the functional group –. It is the isomer of the related nitrile (–C≡N), hence the prefix is ''isocyano''.IUPAC Goldboo''isocyanides''/ref> The organic fragme ...

s. Diphosgene serves as a source of two equivalents of phosgene: :2 RNH₂ + ClCO₂CCl₃ → 2 RNCO + 4 HCl With α-

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s diphosgene gives the acid chloride-isocyanates, OCNCHRCOCl, or ''N''-carboxy-amino acid anhydrides depending on the conditions. It hydrolyzes to release HCl in humid air. Diphosgene is used in some laboratory preparations because it is easier to handle than phosgene.

Role in warfare

Diphosgene was originally developed as a

pulmonary agent A pulmonary agent, or choking agent, is a chemical weapon agent designed to impede a victim's ability to breathe. Such compounds operate by causing a build-up of fluids in the lungs, which then leads to asphyxiation. Exposure of the eyes and sk ...

for chemical warfare, a few months after the first use of phosgene. It was used as a poison gas in

artillery Artillery consists of ranged weapons that launch Ammunition, munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during sieges, and l ...

shells by

Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...

during

World War I World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...

. The first recorded battlefield use was in May 1916. Diphosgene was developed because the vapors could destroy the filters of the

gas mask A gas mask is a piece of personal protective equipment used to protect the wearer from inhaling airborne pollutants and toxic gases. The mask forms a sealed cover over the nose and mouth, but may also cover the eyes and other vulnerable soft ...

s in use at the time.

Safety

Diphosgene has a relatively high

vapor pressure Vapor pressure or equilibrium vapor pressure is the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phases (solid or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indicat ...

of 10 mm Hg (1.3 kPa) at 20 °C and decomposes to

around 300 °C. Exposure to diphosgene is similar in hazard to phosgene.

References

External links

medical care guide

includes treatment advice
material safety data sheet
(PDF, for phosgene and diphosgene treated as one).
MSDS for diphosgene specifically
{{Chemical warfare Pulmonary agents Chloroformates Trichloromethyl esters Carbon oxohalides

Production and uses

Role in warfare

Safety

See also

References

External links