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			{{Short description|Toxic gaseous compound (COCl2)}}
	{{distinguish|phosphine|oxalyl chloride|phosgene oxime}}
			{{redirect|COCl2|the compound {{chem2|CoCl2}}|Cobalt(II) chloride}}
	{{chembox
			{{distinguish|phosphine|phosphene|oxalyl chloride|phosgene oxime}}
			{{Chembox
	| Watchedfields = changed		| Watchedfields = changed
	| verifiedrevid = 400848548		| verifiedrevid = 444050518
	| Reference=<ref>'']'', 11th Edition, '''7310'''.</ref>		| Reference=<ref>'']'', 11th Edition, '''7310'''.</ref>
	| Name = Phosgene		| Name = Phosgene
	| ImageFileL1_Ref = {{chemboximage|correct|??}}		| ImageFile1_Ref = {{chemboximage|correct|??}}
	| ImageFileL1 = Phosgene-dimensions-2D.svg		| ImageFile1 = Phosgene-dimensions-2D.svg
			| ImageName1 = Full structural formula with dimensions
	| ImageSizeL1 = 120px
	| ImageFileR1 = Phosgene-3D-vdW.png		| ImageFile2 = Phosgene-3D-vdW.png
			| ImageName2 = Space-filling model
	| ImageSizeR1 = 100px
			| ImageFile3 = Smelling Case of War Gases, Clifton Park Museum.jpg
	| IUPACName = Carbonyl dichloride
			| ImageCaption3 = A sample case of toxic gases used in chemical warfare; the leftmost contains phosgene in a sealed capillary
	| OtherNames = CG; carbon dichloride oxide; carbon oxychloride; chloroformyl chloride; dichloroformaldehyde; dichloromethanone
			| PIN = Carbonyl dichloride<ref name=iupac2013>{{cite book |title=Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book) |publisher=] |location=Cambridge |date=2014 |page=798 |isbn=978-0-85404-182-4 |doi=10.1039/9781849733069-FP001}}</ref>
	| Section1 = {{Chembox Identifiers
			| OtherNames = {{ubl|Carbon dichloride oxide|Carbon oxychloride|Carbonyl chloride|CG|Chloroformyl chloride|Collongite|Dichloroformaldehyde|Dichloromethanal|Dichloromethanone}}
	| ChEBI = 29365
			|Section1={{Chembox Identifiers
			| ChEBI_Ref = {{ebicite|correct|EBI}}
			| ChEBI = 29365
	| SMILES = ClC(Cl)=O		| SMILES = ClC(Cl)=O
	| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}		| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
	| ChemSpiderID = 6131		| ChemSpiderID = 6131
	| UNII_Ref = {{fdacite|correct|FDA}}		| UNII_Ref = {{fdacite|correct|FDA}}
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	| StdInChIKey = YGYAWVDWMABLBF-UHFFFAOYSA-N		| StdInChIKey = YGYAWVDWMABLBF-UHFFFAOYSA-N
	| CASNo = 75-44-5		| CASNo = 75-44-5
	| CASNo_Ref = {{cascite|correct|CAS}}		| CASNo_Ref = {{cascite|correct|CAS}}
	| RTECS = SY5600000		| RTECS = SY5600000
	| EINECS = 200-870-3		| EINECS = 200-870-3
	| UNNumber = 1076		| UNNumber = 1076
	| PubChem = 6371		| PubChem = 6371
	}}
	| Section2 = {{Chembox Properties
	| Formula = CCl<sub>2</sub>O
	| MolarMass = 98.92 g mol<sup>-1</sup>
	| Appearance = colorless gas
	| Density = 4.248 g/L (15 °C, gas)<br>1.432 g/cm<sup>3</sup> (0 °C, liquid)
	| Solubility = hydrolysis
	| SolubleOther = soluble in ], ], ] <br> decomposes in ] and ]
	| MeltingPtC = −118
	| BoilingPtC = 8.3
	}}
	| Section3 = {{Chembox Structure
	| MolShape = Planar, trigonal
	| Dipole = 1.17 ]
	}}
	| Section7 = {{Chembox Hazards
	| ExternalMSDS =
	| EUIndex = 006-002-00-8
	| EUClass = Very toxic ('''T+''')
	| RPhrases = {{R26}} {{R34}}
	| SPhrases = {{S1/2}} {{S9}} {{S26}} {{S36/37/39}} {{S45}}
	| NFPA-H = 4
	| NFPA-F = 0
	| NFPA-R = 1
	| FlashPt = non-flammable
	| TLV = 0.1 ppm
	}}
	| Section8 = {{Chembox Related
	| OtherCpds = ]<br/>]<br/>]<br/>]<br/>]<br/>]
	}}
	}}		}}
			|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/>
			| Density = 4.248{{nbsp}}g/L (15&nbsp;°C, gas)<br>1.432{{nbsp}}g/cm<sup>3</sup> (0&nbsp;°C, liquid)
			| Solubility = Insoluble, reacts<ref>{{cite web |url=http://www.inchem.org/documents/icsc/icsc/eics0007.htm |title=PHOSGENE (cylinder) |work=Inchem (Chemical Safety Information from Intergovernmental Organizations) |publisher=International Programme on Chemical Safety and the European Commission}}</ref>
			| SolubleOther = Soluble in ], ], ]<br>Decomposes in ] and ]
			| MeltingPtC = −118
			| BoilingPtC = 8.3
			| VaporPressure = 1.6{{nbsp}}atm (20°C)<ref name=PGCH/>
			| MagSus = −48·10<sup>−6</sup> cm<sup>3</sup>/mol
			}}
			|Section3={{Chembox Structure
			| MolShape = ]
			| Dipole = 1.17{{nbsp}}]
			}}
			|Section7={{Chembox Hazards
			| ExternalSDS =
			| GHSPictograms = {{GHS05}}{{GHS06}}<ref name="GESTIS">{{GESTIS|ZVG=1340 |CAS=75-44-5 |Name=Phosgene |Date=16 March 2021 }}</ref>
			| GHSSignalWord = '''Danger'''
			| HPhrases = {{H-phrases|330|314}}<ref name=GESTIS/>
			| PPhrases = {{P-phrases|260|280|303+361+353+315|304+340+315|305+351+338+315|403|405}}<ref name=GESTIS/>
			| NFPA-H = 4
			| NFPA-F = 0
			| NFPA-R = 1
			| FlashPt = ]
			| TLV = 0.1{{nbsp}}] (1 ppm = 4 ]/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>) <ref name=PGCH/>
			| LC50 = {{ubl|500{{nbsp}}ppm (human, 1{{nbsp}}min)|340{{nbsp}}ppm (rat, 30{{nbsp}}min)|438{{nbsp}}ppm (mouse, 30{{nbsp}}min)|243{{nbsp}}ppm (rabbit, 30{{nbsp}}min)|316{{nbsp}}ppm (guinea pig, 30{{nbsp}}min)|1022{{nbsp}}ppm (dog, 20{{nbsp}}min)|145{{nbsp}}ppm (monkey, 1{{nbsp}}min)|1{{nbsp}}ppm is 4{{nbsp}}mg/m<sup>3</sup>}}<ref name=IDLH>{{IDLH|75445|Phosgene}}</ref>
			| LCLo = {{ubl|3{{nbsp}}ppm (human, 2.83{{nbsp}}h)|30{{nbsp}}ppm (human, 17{{nbsp}}min)|50{{nbsp}}ppm (mammal, 5{{nbsp}}min)|88{{nbsp}}ppm (human, 30{{nbsp}}min)|46{{nbsp}}ppm (cat, 15{{nbsp}}min)|50{{nbsp}}ppm (human, 5{{nbsp}}min)|2.7{{nbsp}}ppm (mammal, 30{{nbsp}}min)|1{{nbsp}}ppm is 4{{nbsp}}mg/m<sup>3</sup>}}<ref name=IDLH/>
			}}
			|Section8={{Chembox Related
			| OtherCompounds = {{ubl|]|]|]|]|]|]|]}}
			}}
			}}
			'''Phosgene''' is an ] with the ] {{chem2|COCl2}}. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass.<ref> May 27, 2009</ref> It can be thought of chemically as the double ] analog of ], or structurally as ] with the hydrogen atoms replaced by chlorine atoms. In 2013, about 75–80 % of global phosgene was consumed for ]s, 18% for ]s and about 5% for other ].<ref>{{Cite book |title=Best Available Techniques (BAT) reference document for the production of large volume organic chemicals |date=2017 |publisher= EU Publications Office |isbn=978-92-79-76589-6 |editor-last=Falcke |editor-first=Heino |location=Luxembourg |pages=443 |editor-last2=Holbrook |editor-first2=Simon |editor-last3=Clenahan |editor-first3=Iain |editor-last4=López Carretero |editor-first4=Alfredo |editor-last5=Sanalan |editor-first5=Teoman |editor-last6=Brinkmann |editor-first6=Thomas |editor-last7=Roth |editor-first7=Joze |editor-last8=Zerger |editor-first8=Benoit |editor-last9=Roudier |editor-first9=Serge}}</ref>
			Phosgene is extremely poisonous and was used as a ] during ], where it was ]. It is a highly potent pulmonary irritant and quickly filled enemy trenches due to it being a heavy gas.
	'''Phosgene''' is the ] with the ] COCl<sub>2</sub>. This colorless gas gained infamy as a ] during ]. It is also a valued industrial reagent and building block in ] of pharmaceuticals and other ]s. In low concentrations, its odor resembles freshly cut hay or grass.<ref> May 27, 2009</ref> In addition to its industrial production, small amounts occur naturally from the breakdown and the ] of ]s, such as those used in ] systems.<ref name=Ullmann>Wolfgang Schneider and Werner Diller "Phosgene" in Ullmann's Encyclopedia of Industrial Chemistry Wiley-VCH, Weinheim, 2002. {{DOI| 10.1002/14356007.a19_411}}.</ref> The name, sounding similar to "phosphine", does not mean it has any phosphorus. The chemical was named by combining the Greek words ‘phos’ (meaning light) and genesis (birth).		It is classified as a ] under the ]. In addition to its industrial production, small amounts occur from the breakdown and the ] of ], such as ].<ref name=Ullmann>{{Ullmann |author1= Wolfgang Schneider |author2= Werner Diller |title= Phosgene |doi= 10.1002/14356007.a19_411}}</ref>
	==Structure and basic properties==		==Structure and basic properties==
	Phosgene is a planar molecule as predicted by ]. The C=O distance is 1.18 ], the C---Cl distance is 1.74 Å and the Cl---C---Cl angle is 111.8°.<ref>{{cite journal | author = Nakata, M.; Kohata, K.; Fukuyama, T.; 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 = ] | year = 1980 | volume = 83 | pages = 105–117 | doi=10.1016/0022-2852(80)90314-8}}</ref> It is one of the simplest ]s, being formally derived from ].		Phosgene is a planar molecule as predicted by ]. The C=O distance is 1.18&nbsp;], the C−Cl distance is 1.74&nbsp;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= ] |year= 1980 |volume= 83 |pages= 105–117 |doi=10.1016/0022-2852(80)90314-8}}</ref> Phosgene is a ] and it can be considered one of the simplest acyl chlorides, being formally derived from ].
	==Production==		== Production ==
	Industrially, phosgene is produced by passing purified ] and ] gas through a bed of porous ], which serves as a ]:<ref name=Ullmann/>		Industrially, phosgene is produced by passing purified ] and ] gas through a bed of porous ], which serves as a ]:<ref name=Ullmann/>
	:CO + Cl<sub>2</sub> → COCl<sub>2</sub> (ΔH<sub>rxn</sub> = −107.6kJ/mol)		:{{chem2|CO + Cl2 → COCl2}} (Δ''H''<sub>rxn</sub> = −107.6 kJ/mol)
	The reaction is exothermic, therefore the reactor must be cooled. Typically, the reaction is conducted between 50 and 150 °C. Above 200 °C, phosgene reverts to carbon monoxide and chlorine, K<sub>eq</sub> (300K) = 0.05. Approximately 5000 tonnes were produced in 1989.
			This reaction is exothermic and is typically performed between 50 and 150&nbsp;°C. Above 200&nbsp;°C, phosgene reverts to carbon monoxide and chlorine, ''K''<sub>eq</sub>(300&nbsp;K) = 0.05. World production of this compound was estimated to be 2.74 million tonnes in 1989.<ref name=Ullmann/>
	Because of safety issues, phosgene is almost always produced and consumed within the same plant and extraordinary measures are made to contain this toxic gas. It is listed on ] of the ]: All production sites manufacturing more than 30 tonnes per year must be declared to the ].<ref></ref> Although less dangerous than many other ], such as ], phosgene is still regarded as a viable ] because it is so easy to manufacture when compared to the production requirements of more technically advanced chemical weapons such as the first-generation ] ].
			Phosgene is fairly simple to produce, but is listed as a ] under the ]. As such, it is usually considered too dangerous to transport in ]. 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>
	===Adventitious occurrence===
	Upon ] (UV) radiation in the presence of ], ] slowly converts into phosgene via a ]. To suppress this ], chloroform is often stored in brown-tinted glass containers. Chlorinated compounds used to remove oil from metals, such as automotive brake cleaners, are converted to phosgene by the UV rays of ] processes.
			=== Inadvertent generation ===
	Phosgene may also be produced during testing for leaks of older-style refrigerant gasses. ] (], ] and others) were formerly leak-tested in situ by employing a small gas torch (], ] or ] gas) with a sniffer tube and a copper reaction plate in the flame nozzle of the torch. If any refrigerant gas was leaking from a pipe or joint, the gas would be sucked into the flame via the sniffer tube and would cause a colour change of the gas flame to a bright greenish blue. In the process, phosgene gas would be created due to the thermal reaction. No valid statistics are available, but anecdotal reports suggest that numerous refrigeration technicians suffered the effects of phosgene poisoning due to their ignorance of the toxicity of phosgene, produced during such leak testing. Electronic sensing of refrigerant gases phased out the use of flame testing for leaks in the 1980s. Similarly, phosgene poisoning is a consideration for people fighting fires that are occurring in the vicinity of freon refrigeration equipment, smoking in the vicinity of a freon leak, or fighting fires using ] or halotron.
			====Atmospheric chemistry====
			Simple ]s slowly convert into phosgene when exposed to ] (UV) irradiation in the presence of ].<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 ] in the late 1970s large quantities of organochlorides were routinely used by industry, which inevitably led to them entering the atmosphere. In the 1970-80s phosgene levels in the ] were around 20-30 ] (peak 60 pptv).<ref name=Singh /> These levels had not decreased significantly nearly 30 years later,<ref>{{cite journal |last1=Fu |first1=Dejian |last2=Boone |first2=Chris D. |last3=Bernath |first3=Peter F. |last4=Walker |first4=Kaley A. |last5=Nassar |first5=Ray |last6=Manney |first6=Gloria L. |last7=McLeod |first7=Sean D. |title=Global phosgene observations from the Atmospheric Chemistry Experiment (ACE) mission |journal=Geophysical Research Letters |date=14 September 2007 |volume=34 |issue=17 |pages=L17815 |doi=10.1029/2007GL029942|bibcode=2007GeoRL..3417815F |s2cid=44164908 |doi-access=free }}</ref> despite organochloride production becoming restricted under the ].
			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 ], where it is expected to have a lifetime of several years, since this layer is much drier and phosgene decomposes slowly through UV ]. It plays a minor part in ].
	==Uses==
	The great majority of phosgene is used in the production of ]s, the most important being ] (TDI) and ] (MDI). These isocyanates are precursors to ]s. Significant amounts are also used in the production of ]s via its reaction with ].<ref name=Ullmann/> ]s are an important class of engineering ] found, for example, in lenses in eye glasses.
	===Organic synthesis===		====Combustion====
			] ({{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 ].<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 ].<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" />
	Although phosgene still finds use in ], a variety of substitutes have been developed, notably trichloromethyl chloroformate (“]”), which is a liquid at room temperature, and bis(trichloromethyl) carbonate (“]”), a crystalline substance.<ref>Hamley, P. "Phosgene" Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley, New York. {{DOI| 10.1002/047084289X.rp149}}</ref> The following are the three most useful reactions involving phosgene.
	====Synthesis of carbonates====		====Biologically====
			Phosgene is also formed as a metabolite of ], likely via the action of ].<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>
	]s react with phosgene to give either linear or cyclic carbonates (R = H, alkyl, aryl):
	:HOCR<sub>2</sub>-X-CR<sub>2</sub>OH + COCl<sub>2</sub> → 1/n <sub>n</sub> + 2 HCl
			==History==
	====Synthesis of isocyanates====
			Phosgene was synthesized by the ] chemist ] (1790–1868) in 1812 by exposing a mixture of carbon monoxide and chlorine to ]. He named it "phosgene" from ] {{lang|grc|φῶς}} ({{lang|grc-Latn|phos}}, light) and {{lang|grc|γεννάω}} ({{lang|grc-Latn|gennaō}}, to give birth) in reference of the use of light to promote the reaction.<ref>{{cite journal |title= On a gaseous compound of carbonic oxide and chlorine |author= John Davy |journal= Philosophical Transactions of the Royal Society of London |volume= 102 |year= 1812 |pages= 144–151 |url= https://babel.hathitrust.org/cgi/pt?id=mdp.39015034564289;view=1up;seq=162 |doi= 10.1098/rstl.1812.0008 |jstor=107310|doi-access= free }} Phosgene was named on p. 151: " ... it will be necessary to designate it by some simple name. I venture to propose that of phosgene, or phosgene gas; from {{lang|grc|φως}}, light, {{lang|grc|γινομαι}}, to produce, which signifies formed by light; ... "</ref> It gradually became important in the chemical industry as the 19th century progressed, particularly in dye manufacturing.
	The synthesis of ]s from amines illustrates the ] character of this reagent and its use in introducing the equivalent of "CO<sup>2+</sup>" (R = ], ]):
	<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>
	:RNH<sub>2</sub> + COCl<sub>2</sub> → RN=C=O + 2 HCl
	Such reactions are conducted in the presence of a base such as ] that absorbs the ].
			==Reactions and uses==
	====Synthesis of acid chlorides====
			The reaction of an organic substrate with phosgene is called '''phosgenation'''.<ref name=Ullmann/> Phosgenation of ]s give carbonates (R = ], ], ]), which can be either linear or cyclic:
	It is also used to produce ]s and ] from ]s:
			:{{chem2|''n'' HO\sCR2\sX\sCR2\sOH + ''n'' COCl2 → _{''n''} + 2''n'' HCl}}
	:RCO<sub>2</sub>H + COCl<sub>2</sub> → RC(O)Cl + HCl + CO<sub>2</sub>
			An example is the reaction of phosgene with ] to form ]s.<ref name="Ullmann" /> Phosgenation of diamines gives di-isocyanates, like ] (TDI), ] (MDI), ] (HDI), and ] (IPDI). In these conversions, phosgene is used in excess to increase yield and minimize side reactions. The phosgene excess is separated during the work-up of resulting end products and recycled into the process, with any remaining phosgene decomposed in water using ] as the catalyst. Diisocyanates are precursors to ]. More than 90% of the 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 ], ], and ]. Phosgene is also used to produce monoisocyanates, used as pesticide precursors (''e.g.'' ] (MIC).
	Such acid chlorides react with amines and alcohols to give, respectively, amides and esters, which are commonly used intermediates. ] is more commonly and more safely employed for this application. A specific application for phosgene is the production of chloroformic esters:
	:ROH + COCl<sub>2</sub> → ROC(O)Cl + HCl
			Aside from the widely used reactions described above, phosgene is also used to produce ]s from ]s:
	===Inorganic chemistry===
			:{{chem2|R\sC(\dO)\sOH + COCl2 → R\sC(\dO)\sCl + HCl + CO2}}
	Although it is somewhat hydrophobic, phosgene reacts with ] to release ] and ]:
			For this application, ] is commonly used instead of phosgene.
	:COCl<sub>2</sub> + H<sub>2</sub>O → CO<sub>2</sub> + 2 HCl
	Analogously, with ammonia, one obtains ]:
	:COCl<sub>2</sub> + 4 NH<sub>3</sub> → CO(NH<sub>2</sub>)<sub>2</sub> + 2 NH<sub>4</sub>Cl
	Halide exchange with ] and ] gives ] and ], respectively.<ref name=Ullmann/>
			===Laboratory uses===
	==History==
			The synthesis of ]s from amines illustrates the ] character of this reagent and its use in introducing the equivalent ] "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>
	Phosgene was synthesized by the ] chemist ] (1790–1868) in 1812 by exposing a mixture of carbon monoxide and chlorine to ]. He named it "phosgene" in reference of the use of light to promote the reaction; from ], ''phos'' (light) and ''gene'' (born).<ref>{{cite journal
			:{{chem2|R\sNH2 + COCl2 → R\sN\dC\dO + 2 HCl}}, where R = ], ]
	| title = On a Gaseous Compound of Carbonic Oxide and Chlorine
			Such reactions are conducted on laboratory scale in the presence of a base such as ] that neutralizes the ] side-product.
	| author = John Davy
	| journal = Philosophical Transactions of the Royal Society of London
			Phosgene is used to produce ]s such as ]:
	| volume = 102
			:{{chem2|R\sOH + COCl2 → R\sO\sC(\dO)\sCl + HCl}}
	| year = 1812
			In these syntheses, phosgene is used in excess to prevent formation of the corresponding ].
	| pages = 144–151
	| doi = 10.1098/rstl.1812.0008
			With ]s, phosgene (or its trimer) reacts to give ]s. More generally, phosgene acts to link two nucleophiles by a carbonyl group. For this purpose, alternatives to phosgene such as ] (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 ].
	| jstor=107310}}</ref> It gradually became important in the chemical industry as the 19th century progressed, particularly in dye manufacturing.
			Phosgene is stored in ]. In the US, the cylinder valve outlet is a tapered thread known as "] 160" that is used only for phosgene.
			===Alternatives to phosgene===
			In the research laboratory, due to safety concerns phosgene nowadays finds limited use in ]. A variety of substitutes have been developed, notably trichloromethyl chloroformate ("]"), a liquid at room temperature, and bis(trichloromethyl) carbonate ("]"), 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 ] to release ] and ]:
			:{{chem2|COCl2 + H2O → CO2 + 2 HCl}}
			Analogously, upon contact with ammonia, it converts to ]:
			:{{chem2|COCl2 + 4 NH3 → CO(NH2)2 + 2 Cl}}
			Halide exchange with ] and ] gives ] and ], respectively.<ref name=Ullmann/>
	===Chemical warfare===		===Chemical warfare===
			]]]
	{{further|]|]}}
			{{Further|Chemical weapons in World War I|Second Italo-Ethiopian War}}
	Following the extensive use of phosgene gas in combat during ], it was stockpiled by various countries as part of their secret chemical weapons programs.<ref>, ''Lithgow Mercury'', 7/08/2008</ref><ref>, ''Lithgow Mercury'', 9/09/2008</ref><ref>, ''The Daily Telegraph'', September 22, 2008</ref>
			It is listed on ] of the ]: All production sites manufacturing more than 30 tonnes per year must be declared to the ].<ref> {{webarchive|url=https://web.archive.org/web/20060515151142/http://www.opcw.org/html/db/cwc/eng/cwc_annex_verification_part_VIII.html |date=2006-05-15}}.</ref> Although less toxic than many other ]s such as ], phosgene is still regarded as a viable ] because of its simpler manufacturing requirements when compared to that of more technically advanced chemical weapons such as ], a first-generation ].<ref>https://itportal.decc.gov.uk/cwc_files/S2AAD_guidance.pdf {{Webarchive|url=https://web.archive.org/web/20160304042624/https://itportal.decc.gov.uk/cwc_files/S2AAD_guidance.pdf |date=2016-03-04 }}.</ref>
	Phosgene was then only frequently used by the ] against the Chinese during the ].<ref>Yuki Tanaka, ''Poison Gas, the Story Japan Would Like to Forget,'' Bulletin of the Atomic Scientists, October 1988, p. 16-17</ref> Gas weapons, such as phosgene, were produced by ] and authorized by specific orders given by Hirohito (]) himself, transmitted by the ]. For example, the Emperor authorized the use of toxic gas on 375 separate occasions during the ] from August to October 1938.<ref>Y. Yoshimi and S. Matsuno, ''Dokugasusen Kankei Shiryô II, Kaisetsu, Jugonen Sensô Gokuhi Shiryoshu'', 1997, p.27-29</ref>
			Phosgene was first deployed as a chemical weapon by the French in 1915 in World War I.<ref>{{cite book |first=Mary Jo |last=Nye |year=1999 |page=193 |title=Before big science: the pursuit of modern chemistry and physics, 1800–1940 |publisher=Harvard University Press |isbn=0-674-06382-1}}</ref> It was also used in a mixture with an equal volume of chlorine, with the chlorine helping to spread the denser phosgene.<ref name="cbwinfo">{{cite web |author=Staff |year=2004 |url=http://cbwinfo.com/Chemical/Pulmonary/CG.shtml |title=Choking Agent: CG |publisher=CBWInfo |access-date=2007-07-30 |url-status=dead |archive-url=https://web.archive.org/web/20060218124704/http://cbwinfo.com/Chemical/Pulmonary/CG.shtml |archive-date=2006-02-18 }}</ref><ref>{{cite book |author=Kiester, Edwin |title=An Incomplete History of World War I |page=74 |volume=1 |publisher=Murdoch Books |year=2007 |isbn=978-1-74045-970-9 |display-authors=etal}}</ref> Phosgene was more potent than chlorine, though some symptoms took 24 hours or more to manifest.
	==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
	| author = Borak J., 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
	}}</ref>
	Phosgene can be detected at 0.4 ppm, which is four times the ]. Its high ] arises from the action of the phosgene on the ]s in the pulmonary ], which are the site of gas exchange: their damage disrupts the ], causing suffocation. It reacts with the ]s of the proteins, causing crosslinking via formation of ]-like linkages, in accord with the reactions discussed above. Phosgene detection badges are worn by those at risk of exposure.<ref name=Ullmann/>
			Following the extensive use of phosgene during ], it was stockpiled by various countries.<ref>, ''Lithgow Mercury'', 7/08/2008</ref><ref> {{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>, ''The Daily Telegraph'', September 22, 2008</ref>
	] may be used to neutralise liquid spills of phosgene. Gaseous spills may be mitigated with ].<ref>{{cite web | publisher = ] | title = Phosgene: Health and Safety Guide | year = 1998 | url = http://www.inchem.org/documents/hsg/hsg/hsg106.htm}}</ref>
			Phosgene was then only infrequently used by the ] against the ] during the ].<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 ].
			==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>
			At low concentrations, phosgene 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 ] for phosgene is 0.4 ppm, four times the ] (time weighted average). Its high ] arises from the action of the phosgene on the {{chem2|\sOH}}, {{chem2|\sNH2}} and {{chem2|\sSH}} groups of the ]s in pulmonary ] (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 ], eventually causing ]. 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>
			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 ] often develops which can be detected by ] and regressive ]. Inhalation of such high doses can eventually result in fatality within hours up to 2–3 days of the exposure.
			The risk connected to a phosgene inhalation is based not so much on its toxicity (which is much lower in comparison to modern chemical weapons like ] or ]) but rather on its typical effects: the affected person may not develop any symptoms for hours until an edema appears, at which point it could be too late for medical treatment to assist.<ref>W. F. Diller: ''Radiologische Untersuchungen zur verbesserten Frühdiagnose von industriellen Inhalationsvergiftungen mit verzögertem Wirkungseintritt, Verlag für Medizin Dr. E. Fischer, Heidelberg. Zentralbatt für Arbeitsmedizin, Arbeitsschutz und Ergonomie, Nr. 3, Mai 2013, p. 160 - 163''</ref> Nearly all fatalities as a result of accidental releases from the industrial handling of phosgene occurred in this fashion. On the other hand, pulmonary edemas treated in a timely manner usually heal in the mid- and longterm, without major consequences once some days or weeks after exposure have passed.<ref>W.F. Diller, F. Schnellbächer, F. Wüstefeld : Zentralbl. Arbeitsmed. Arbeitsschutz Prophyl. 29 (1979) p.5-16</ref><ref>Results From the US Industry-Wide Phosgene Surveillance "The Diller Registry" : Journal of Occ. and Env. Med., March 2011-Vol.53-iss. 3 p.239- 244</ref> Nonetheless, the detrimental health effects on pulmonary function from untreated, chronic low-level exposure to phosgene should not be ignored; although not exposed to concentrations high enough to immediately cause an edema, many synthetic chemists (''e.g.'' ]) working with the compound were reported to experience chronic respiratory health issues and eventual respiratory failure from continuous low-level exposure.
			If accidental release of phosgene occurs in an industrial or laboratory setting, it can be mitigated with ] gas; in the case of liquid spills (''e.g.'' of diphosgene or phosgene solutions) an absorbent and sodium carbonate can be applied.<ref>{{cite web |publisher= ] |title= Phosgene: Health and Safety Guide |year= 1998 |url= http://www.inchem.org/documents/hsg/hsg/hsg106.htm}}</ref>
			==Accidents==
			*The first major phosgene-related incident happened in May 1928 when eleven tons of phosgene escaped from a war surplus store in central ].<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=–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 ] for the ], but investigations proved ] 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 ] facility in ] killed one employee in 2010.<ref>{{Cite web|url=https://www.csb.gov/dupont-corporation-toxic-chemical-releases/|title=DuPont Corporation Toxic Chemical Releases &#124; CSB}}</ref> The ] 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 ] plant in ], where a contractor inhaled a lethal dose of phosgene.<ref>Archived at {{cbignore}} and the {{cbignore}}: {{cite web| url = https://www.youtube.com/watch?v=ISNGimMXL7M| title = Fatal Exposure: Tragedy at DuPont | website=]| date = 22 September 2011 }}{{cbignore}}</ref>
			*]: A freight train carrying ] derailed and burned in ], releasing phosgene and ] into the air and contaminating the ].<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 13, 2023 |archive-url=https://web.archive.org/web/20230213091852/https://www.theguardian.com/us-news/2023/feb/11/ohio-train-derailment-wake-up-call |url-status=live }}</ref>
			==See also==
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	==References==		==References==
	{{reflist}}
			{{Reflist}}
	==External links==		==External links==
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	*, OPCW website		*, OPCW website
	*		*
	* (Refer to Section 4.C of the article)		*
	*		*
	{{chemical warfare}}		{{Chemical agents}}
	{{U.S. chemical weapons}}		{{U.S. chemical weapons}}
			{{Authority control}}
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