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This chemical does not appear to be generally related to those topics, and this specific chunk of content definitely is not. But regardless, I will happily take ownership of the edit if necessary. Undid revision 1236516456 by 2600:100F:B10C:8CFD:4B12:E60:51CC:101 (talk) |
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| ImageName2 = Space-filling model
| ImageFile3 = Smelling Case of War Gases, Clifton Park Museum.jpg
| ImageCaption3 = A
| PIN = Carbonyl dichloride<ref name=iupac2013>{{cite book |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book) |publisher=[[Royal Society of Chemistry]] |location=Cambridge |date=2014 |page=798 |isbn=978-0-85404-182-4 |doi=10.1039/9781849733069-FP001|doi-broken-date=2024-05-09 }}</ref>
| OtherNames = {{ubl|Carbon dichloride oxide|Carbon oxychloride|Carbonyl chloride|CG|Chloroformyl chloride|Collongite|Dichloroformaldehyde|Dichloromethanal|Dichloromethanone}}
|Section1={{Chembox Identifiers
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}}
|Section8={{Chembox Related
| OtherCompounds = {{ubl|[[Thiophosgene]]|[[Formaldehyde]]|[[Carbonic acid]]|[[Urea]]|[[Carbon monoxide]]|[[Chloroformic acid]]|[[Phosgene oxime]]}}
}}
}}
'''Phosgene''' is an [[organic chemical compound]] with the [[chemical formula|formula]]
Phosgene is extremely poisonous and was used as a [[chemical weapon]] during [[World War I]], where it was [[Chemical weapons in World War I|responsible for 85,000 deaths]]. It is a highly potent pulmonary irritant and quickly filled enemy trenches due to it being a heavy gas.
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==Structure and basic properties==
Phosgene is a planar molecule as predicted by [[VSEPR theory]]. The C=O distance is 1.18 [[angstrom (unit)|Å]], the C−Cl distance is 1.74 Å and the Cl−C−Cl angle is 111.8°.<ref>{{cite journal |author1=Nakata, M. |author2=Kohata, K. |author3=Fukuyama, T. |author4=Kuchitsu, K. |title= Molecular Structure of Phosgene as Studied by Gas Electron Diffraction and Microwave Spectroscopy. The ''r<sub>z</sub>'' Structure and Isotope Effect |journal= [[Journal of Molecular Spectroscopy]] |year= 1980 |volume= 83 |pages= 105–117 |doi=10.1016/0022-2852(80)90314-8}}</ref> Phosgene is a [[carbon oxohalide]] and it can be considered one of the simplest acyl chlorides, being formally derived from [[carbonic acid]].
== Production ==
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This reaction is exothermic and is typically performed between 50 and 150 °C. Above 200 °C, phosgene reverts to carbon monoxide and chlorine, ''K''<sub>eq</sub>(300 K) = 0.05. World production of this compound was estimated to be 2.74 million tonnes in 1989.<ref name=Ullmann/>
Phosgene is fairly simple to produce, but is listed as a [[List of Schedule 3 substances (CWC)|Schedule 3 substance]] under the [[Chemical Weapons Convention]]. As such, it is usually considered too dangerous to transport in [[Bulk cargo|bulk quantities]]. Instead, phosgene is usually produced and consumed within the same plant, as part of an "on demand" process. This involves maintaining equivalent rates of production and consumption, which keeps the amount of phosgene in the system at any one time fairly low, reducing the risks in the event of an accident. Some batch production does still take place, but efforts are made to reduce the amount of phosgene stored.<ref>{{cite journal |last=Gowland |first=Richard |title=Applying inherently safer concepts to a phosgene plant acquisition |journal=Process Safety Progress |date=1996 |volume=15 |issue=1 |pages=52–57 |s2cid=110707551 |doi=10.1002/prs.680150113}}</ref>
=== Inadvertent generation ===
====Atmospheric chemistry====
Simple [[organochloride]]s slowly convert into phosgene when exposed to [[ultraviolet]] (UV) irradiation in the presence of [[oxygen]].<ref name=Singh>{{cite journal |last=Singh |first=Hanwant Bir |title=Phosgene in the ambient air |journal=Nature |date=December 1976 |volume=264 |issue=5585 |pages=428–429 |pmid=1004568 |bibcode=1976Natur.264..428S |s2cid=4209599 |doi=10.1038/264428a0}}</ref> Before the discovery of the [[Ozone hole]] in the late 1970s large quantities of organochlorides were routinely used by industry, which inevitably led to them entering the atmosphere.
Phosgene in the troposphere can last up to about 70 days and is removed primarily by hydrolysis with ambient humidity or cloudwater.<ref>{{cite journal |last1=Kindler |first1=T.P. |last2=Chameides |first2=W.L. |last3=Wine |first3=P.H. |last4=Cunnold |first4=D.M. |last5=Alyea |first5=F.N. |last6=Franklin |first6=J.A. |title=The fate of atmospheric phosgene and the stratospheric chlorine loadings of its parent compounds: CCl 4, C 2 Cl 4, C 2 HCl 3, CH 3 CCl 3, and CHCl 3 |journal=Journal of Geophysical Research: Atmospheres |date=20 January 1995 |volume=100 |issue=D1 |pages=1235–1251 |doi=10.1029/94JD02518|bibcode=1995JGR...100.1235K }}</ref> Less than 1% makes it to the [[stratosphere]], where it is expected to have a lifetime of several years, since this layer is much drier and phosgene decomposes slowly through UV [[Photodissociation|photolysis]]. Consequently, it does play a minor part in [[ozone depletion]].
====Combustion====
[[Carbon tetrachloride]] ({{chem2|CCl4}}) can turn into phosgene when exposed to heat in air. This was a problem as carbon tetrachloride is an effective fire suppressant and was formerly in widespread use in [[Fire extinguisher|fire extinguishers]].<ref name="Burke">{{cite book |last=Burke |first=Robert |title=Fire Protection: Systems and Response |date=2007-11-06 |publisher=CRC Press |isbn=978-0-203-48499-9 |pages=209}}</ref> There are reports of fatalities caused by its use to fight fires in [[Confined space|confined spaces]].<ref>{{cite journal |last1=Fieldner |first1=A. C. |last2=Katz |first2=S. H. |last3=Kinney |first3=S. P. |last4=Longfellow |first4=E. S. |date=1920-10-01 |title=Poisonous gases from carbon tetrachloride fire extinguishers |url=https://www.sciencedirect.com/science/article/pii/S0016003220914941 |access-date=2022-02-03 |journal=Journal of the Franklin Institute |volume=190 |issue=4 |pages=543–565 |language=en |doi=10.1016/S0016-0032(20)91494-1}}</ref> Carbon tetrachloride's generation of phosgene and its own toxicity mean it is no longer used for this purpose.<ref name="Burke" />
====Biologically====
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With [[amino acid]]s, phosgene (or its trimer) reacts to give [[amino acid N-carboxyanhydride]]s. More generally, phosgene acts to link two nucleophiles by a carbonyl group. For this purpose, alternatives to phosgene such as [[carbonyldiimidazole]] (CDI) are safer, albeit expensive.<ref>{{cite journal |last1=Bigi |first1=Franca |last2=Maggi |first2=Raimondo |last3=Sartori |first3=Giovanni |title=Selected syntheses of ureas through phosgene substitutes |journal=Green Chemistry |date=2000 |volume=2 |issue=4 |pages=140–148 |doi=10.1039/B002127J}}</ref> CDI itself is prepared by reacting phosgene with [[imidazole]].
Phosgene is stored in [[Gas cylinder|metal cylinders]]. In the US, the cylinder valve outlet is a tapered thread known as "[[Gas cylinder#Connection|CGA]] 160" that is used only for phosgene.
===Alternatives to phosgene===
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===Chemical warfare===
[[File:"Phosgene,
{{Further|Chemical weapons in World War I|Second Italo-Ethiopian War}}
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Following the extensive use of phosgene during [[World War I]], it was stockpiled by various countries.<ref>[https://archive.today/20120713033614/http://lithgow.yourguide.com.au/news/local/news/general/chemical-warfare-left-its-legacy/1237570.aspx Base's phantom war reveals its secrets], ''Lithgow Mercury'', 7/08/2008</ref><ref>[http://lithgow.yourguide.com.au/news/local/news/general/chemical-warfare-left-its-legacy/1266856.aspx Chemical warfare left its legacy] {{Webarchive|url=https://web.archive.org/web/20081205064323/http://lithgow.yourguide.com.au/news/local/news/general/chemical-warfare-left-its-legacy/1266856.aspx |date=2008-12-05 }}, ''Lithgow Mercury'', 9/09/2008</ref><ref>[http://www.mustardgas.org/wp-content/uploads/Chemical-Warfare-Left-Its-Legacy.pdf Chemical bombs sit metres from Lithgow families for 60 years], ''The Daily Telegraph'', September 22, 2008</ref>
Phosgene was then only infrequently used by the [[Imperial Japanese Army]] against the [[Republic of China (1912–1949)|Chinese]] during the [[Second Sino-Japanese War]].<ref>Yuki Tanaka, "Poison Gas, the Story Japan Would Like to Forget", ''Bulletin of the Atomic Scientists'', October 1988, pp. 16–17</ref> Gas weapons, such as phosgene, were produced by the IJA's [[Unit 731]].
==Toxicology and safety==
Phosgene is an insidious poison as the odor may not be noticed and symptoms may be slow to appear.<ref>{{cite journal |title= Phosgene exposure: mechanisms of injury and treatment strategies |author1=Borak J. |author2=Diller W. F. |journal= Journal of Occupational and Environmental Medicine |year= 2001 |volume= 43 |issue= 2 |pages= 110–9 |pmid= 11227628 |doi= 10.1097/00043764-200102000-00008|s2cid=41169682 }}</ref>
Phosgene at low concentrations, may have a pleasant odor of freshly mown hay or green corn,<ref>{{Cite web |last=CDC |date=2023-08-31 |title=Facts About Phosgene |url=https://emergency.cdc.gov/agent/phosgene/basics/facts.asp |access-date=2024-06-28 |website=emergency.cdc.gov |language=en-us}}</ref> but has also been described as sweet, like rotten banana peels.
The [[odor detection threshold]] for phosgene is 0.4 ppm, four times the [[threshold limit value]] (time weighted average). Its high [[toxicity]] arises from the action of the phosgene on the {{chem2|\sOH}}, {{chem2|\sNH2}} and {{chem2|\sSH}} groups of the [[protein]]s in pulmonary [[Pulmonary alveolus|alveoli]] (the site of gas exchange), respectively forming ester, amide and thioester functional groups in accord with the reactions discussed above. This results in disruption of the [[blood–air barrier]], eventually causing [[pulmonary edema]]. The extent of damage in the alveoli does not primarily depend on phosgene concentration in the inhaled air, with the dose (amount of inhaled phosgene) being the critical factor.<ref name=":0" /> Dose can be approximately calculated as "concentration" × "duration of exposure".<ref name=":0">Werner F. Diller, Early Diagnosis of Phosgene Overexposure.''Toxicology and Industrial Health, Vol.1, Nr.2, April 1985, p. 73 -80''</ref><ref>W. F. Diller, R. Zante : Zentralbl. Arbeitsmed. Arbeitsschutz Prophyl. Ergon. 32, (1982) 60 -368</ref> Therefore, persons in workplaces where there exists risk of accidental phosgene release usually wear indicator badges close to the nose and mouth.<ref name=":1" /> Such badges indicate the approximate inhaled dose, which allows for immediate treatment if the monitored dose rises above safe limits.<ref name=":1">W. F.Diller, E.Drope, E. Reichold: ''Ber. Int. Kolloq. Verhütung von Arbeitsunfällen und Berufskrankheiten Chem. Ind.6 th (1979) Chem. Abstr. 92 (1980) 168366x''</ref>
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==Accidents==
*The first major phosgene-related incident happened in May 1928 when eleven tons of phosgene escaped from a war surplus store in central [[Hamburg]].<ref name=Ryan154/> Three hundred people were poisoned, of whom ten died.<ref name=Ryan154>{{cite book |title=Phosgene and Related Carbonyl Halides |url=https://archive.org/details/phosgenerelatedc00tary |url-access=limited |last=Ryan |first=T.Anthony |year=1996 |publisher= Elsevier |isbn=0444824456 |pages=[https://archive.org/details/phosgenerelatedc00tary/page/n200 154]–155}}</ref>
*In the second half of 20th century several fatal incidents implicating phosgene occurred in Europe, Asia and the US. Most of them have been investigated by authorities and the outcome made accessible to the public. For example, phosgene was initially [[blamed]] for the [[Bhopal disaster]], but investigations proved [[methyl isocyanate]] to be responsible for the numerous poisonings and fatalities.
* Recent major incidents happened in January 2010 and May 2016. An accidental release of phosgene gas at a [[DuPont (1802–2017)|DuPont]] facility in [[West Virginia]] killed one employee in 2010.<ref>{{Cite web|url=https://www.csb.gov/dupont-corporation-toxic-chemical-releases/|title=DuPont Corporation Toxic Chemical Releases | CSB}}</ref> The [[U.S. Chemical Safety Board|US Chemical Safety Board]] released a video detailing the accident.<ref>{{Citation|title=Fatal Exposure: Tragedy at DuPont| date=22 September 2011 |url=https://www.youtube.com/watch?v=ISNGimMXL7M|language=en|access-date=2021-07-02}}</ref> Six years later, a phosgene leak occurred in a [[BASF]] plant in [[South Korea]], where a contractor inhaled a lethal dose of phosgene.<ref>Archived at [https://ghostarchive.org/varchive/youtube/20211205/ISNGimMXL7M Ghostarchive]{{cbignore}} and the [https://web.archive.org/web/20130104204718/http://www.youtube.com/watch?v=ISNGimMXL7M&feature=youtube_gdata Wayback Machine]{{cbignore}}: {{cite web| url = https://www.youtube.com/watch?v=ISNGimMXL7M| title = Fatal Exposure: Tragedy at DuPont | website=[[YouTube]]| date = 22 September 2011 }}{{cbignore}}</ref>
*[[2023 Ohio train derailment]]: A freight train carrying [[vinyl chloride]] derailed and burned in [[East Palestine, Ohio]], releasing phosgene and [[hydrogen chloride]] into the air and contaminating the [[Ohio River]].<ref>{{Cite web |date=February 11, 2023 |title=Ohio catastrophe is 'wake-up call' to dangers of deadly train derailments |url=https://www.theguardian.com/us-news/2023/feb/11/ohio-train-derailment-wake-up-call |website=The Guardian |access-date=February 13, 2023 |archive-date=February
==See also==
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*[[Oxalyl chloride]]
*[[Thiophosgene]]
*[[Thionyl chloride]]
*[[Perfluoroisobutene]]
*[[Bis(trifluoromethyl) disulfide]]
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