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Bernardirfan (talk | contribs) Clarification, Replacing <chem> with {{chem2}} |
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 =
|Section1={{Chembox Identifiers
| ChEBI_Ref = {{ebicite|correct|EBI}}
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|Section2={{Chembox Properties
| Formula = {{chem2|COCl2}}
| C=1|O=1|Cl=2
| Appearance = Colorless gas
| Odor = Suffocating, like musty hay or grass<ref name=PGCH/>
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}}
|Section3={{Chembox Structure
| MolShape =
| Dipole = 1.17{{nbsp}}[[Debye|D]]
}}
|Section7={{Chembox Hazards
| ExternalSDS = [https://produkte.airliquide.de/gasekatalog/sdb/099-DE-DE-Phosgen.pdf]
| GHSPictograms = {{GHS04}}
| GHSSignalWord = '''Danger'''
| HPhrases = {{H-phrases|280|330|314}}<ref name=GESTIS/>
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| NFPA-F = 0
| NFPA-R = 1
| FlashPt = [[Non-flammable]]
| TLV = 0.1{{nbsp}}[[Parts-per notation|ppm]] (1 ppm = 4 [[Milligram|mg]]/m<sup>3</sup>)
| PEL = TWA 0.1{{nbsp}}ppm (0.4{{nbsp}}mg/m<sup>3</sup>)<ref name=PGCH>{{PGCH|0504}}</ref>
| IDLH = 2{{nbsp}}ppm<ref name=PGCH/><br>1 ppm = 4 mg/m<sup>3</sup>
| REL = TWA 0.1{{nbsp}}ppm (0.4{{nbsp}}mg/m<sup>3</sup>) C 0.2{{nbsp}}ppm (0.8{{nbsp}}mg/m<sup>3</sup>) [15-minute]<ref name=PGCH/>
| LC50 = {{ubl|500{{nbsp}}ppm (human, 1{{nbsp}}min)
| LCLo = {{ubl|3{{nbsp}}ppm (human, 2.83{{nbsp}}h)
}}
|Section8={{Chembox Related
| OtherCompounds = {{ubl|[[Thiophosgene]]
}}
}}
'''Phosgene''' is an [[organic chemical compound]] with the [[chemical formula|formula]] {{chem2|COCl2
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 ===
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
[[Carbon tetrachloride]] (
Phosgene is also formed as a metabolite of [[chloroform]], likely via the action of [[cytochrome P-450]].<ref>{{cite journal |last1=Pohl |first1=Lance R. |last2=Bhooshan |first2=B. |last3=Whittaker |first3=Noel F. |last4=Krishna |first4=Gopal |title=Phosgene: A metabolite of chloroform |journal=Biochemical and Biophysical Research Communications |date=December 1977 |volume=79 |issue=3 |pages=684–691 |pmid=597296 |doi=10.1016/0006-291X(77)91166-4}}</ref>
==History==
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==Reactions and uses==
The reaction of an organic substrate with phosgene is called '''phosgenation'''.<ref name=Ullmann/> Phosgenation of [[diol]]s give carbonates (R = [[Hydrogen|H]], [[alkyl]], [[aryl]]), which can be either linear or cyclic:
:{{chem2|''n'' HO\sCR2\sX\sCR2\sOH + ''n'' COCl2 → [\sO\sCR2\sX\sCR2\sO\sC(\dO)\s]_{''n''} + 2''n'' HCl}}
Aside from the widely used reactions described above, phosgene is also used to produce [[acyl chloride]]s from [[carboxylic acid]]s:▼
:{{chem2|R\sC(\dO)\sOH + COCl2 → R\sC(\dO)\sCl + HCl + CO2}}
For this application, [[thionyl chloride]] is commonly used instead of phosgene
===
The synthesis of [[isocyanate]]s from amines illustrates the [[electrophilic]] character of this reagent and its use in introducing the equivalent [[synthon]] "CO<sup>2+</sup>":<ref>{{OrgSynth |author= R. L. Shriner, W. H. Horne, and R. F. B. Cox |title= p-Nitrophenyl Isocyanate |collvol= 2 |collvolpages= 453 |year= 1943 |prep= CV2P0453}}</ref>
:
Such reactions are conducted on laboratory scale in the presence of a base such as [[pyridine]] that neutralizes the [[hydrogen chloride]] side-product.
▲Phosgene is used in industry for the production of aromatic di-isocyanates like [[toluene diisocyanate]] (TDI) and [[methylene diphenyl diisocyanate]] (MDI), which are precursors for production of [[polyurethanes]]. It is also used to form [[polycarbonate]]s, via a reaction with [[bisphenol A]]. More than 90% of the worldwide produced phosgene is used in these processes, with the biggest production units located in the United States (Texas and Louisiana), Germany, Shanghai, Japan, and South Korea. The most important producers are [[Dow Chemical]], [[Covestro]], and [[BASF]]. Phosgene is used in the production of aliphatic diisocyanates such as [[hexamethylene diisocyanate]] (HDI) and [[isophorone diisocyanate]] (IPDI), which are precursors for the production of advanced coatings. Phosgene is also used to produce monoisocyanates, used as pesticide precursors (''e.g.'' [[methyl isocyanate]] (MIC).
In the research laboratory, due to safety concerns phosgene nowadays finds limited use in [[organic synthesis]]. A variety of substitutes have been developed, notably trichloromethyl chloroformate ("[[diphosgene]]"), a liquid at room temperature, and bis(trichloromethyl) carbonate ("[[triphosgene]]"), a crystalline substance.<ref>Hamley, P. "Phosgene" ''Encyclopedia of Reagents for Organic Synthesis'', 2001 John Wiley, New York. {{doi |10.1002/047084289X.rp149}}</ref>▼
▲Aside from the widely used reactions described above, phosgene is also used to produce [[acyl chloride]]s from [[carboxylic acid]]s:
▲For this application, [[thionyl chloride]] is commonly used instead of phosgene in academic settings.
Phosgene is used to produce [[chloroformate]]s such as [[benzyl chloroformate]]:
:
In these syntheses, phosgene is used in excess to prevent formation of the corresponding [[carbonate ester]].
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===
▲In the research laboratory, due to safety concerns phosgene nowadays finds limited use in [[organic synthesis]]. A variety of substitutes have been developed, notably trichloromethyl chloroformate ("[[diphosgene]]"), a liquid at room temperature, and bis(trichloromethyl) carbonate ("[[triphosgene]]"), a crystalline substance.<ref>Hamley, P. "Phosgene" ''Encyclopedia of Reagents for Organic Synthesis'', 2001 John Wiley, New York. {{doi |10.1002/047084289X.rp149}}</ref>
===Other reactions===
Phosgene reacts with [[water]] to release [[hydrogen chloride]] and [[carbon dioxide]]:
:
Analogously, upon contact with ammonia, it converts to [[urea]]:
:
Halide exchange with [[nitrogen trifluoride]] and [[aluminium tribromide]] gives [[carbonyl fluoride|
===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
In case of low or moderate quantities of inhaled phosgene, the exposed person is to be monitored and subjected to precautionary therapy, then released after several hours. For higher doses of inhaled phosgene (above 150 ppm × min) a [[pulmonary edema]] often develops which can be detected by [[Radiography|X-ray imaging]] and regressive [[Oxygen saturation (medicine)|blood oxygen concentration]]. Inhalation of such high doses can eventually result in fatality within hours up to 2–3 days of the exposure.
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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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