PhosgeneFrom Wikipedia, the free encyclopedia"COCl2" redirects here. For the compound CoCl2, seeCobalt(II) chloride.Not to be confused withphosphine,phosphene,oxalyl chloride, orphosgene oxime.Phosgene[1]

Names

IUPAC name : Carbonyl dichloride

Other namesCG; carbon dichloride oxide; carbon oxychloride; Chloroformyl chloride; dichloroformaldehyde; dichloromethanone; dichloromethanal

Identifiers

CAS Registry Number75-44-5

ChEBICHEBI:29365

ChemSpider6131

EC number200-870-3

InChI[show]

Jmol-3D imagesImage

PubChem6371

RTECS numberSY5600000

SMILES[show]

UNII117K140075

UN number1076

Properties

Chemical formulaCOCl2

Molar mass98.92 g mol1

Appearancecolorless gas

Odorsuffocating, like musty hay[2]

Density4.248 g/L (15C, gas) ----- 1.432 g/cm3(0C, liquid)

Melting point118C (180F; 155K)

Boiling point8.3C (46.9F; 281.4K)

Solubility in waterdecomposes in water[3]

Solubilitysoluble inbenzene,toluene,acetic acid ------ decomposes inalcoholandacid

Vapor pressure1.6 atm (20C)[2]

Structure

Molecular shapePlanar, trigonal

Dipole moment1.17D

Hazards

SDSICSC 0007

EU Index006-002-00-8

EU classificationT+

R-phrasesR26R34

S-phrases(S1/2)S9S26S36/37/39S45

NFPA 7044 blue - 0 red - 1 yellow

Flash pointNon-flammable

Threshold Limit Value0.1 ppm

LC50(Median lethal concentration)500 ppm (human, 1 min)340 ppm (rat, 30 min)438 ppm (mouse, 30 min)243 ppm (rabbit, 30 min)316 ppm (guinea pig, 30 min)1022 ppm (dog, 20 min)145 ppm (monkey, 1 min)[4]

US health exposure limits (NIOSH):

PEL (Permissible)TWA 0.1 ppm (0.4 mg/m3)[2]

REL (Recommended)TWA 0.1 ppm (0.4 mg/m3) C 0.2 ppm (0.8 mg/m3) [15-minute][2]

IDLH (Immediate danger)2 ppm[2]

Related compounds

Related compoundsThiophosgeneFormaldehydeCarbonic acidUreaCarbon monoxideChloroformic acid

Except where otherwise noted, data are given for materials in theirstandard state(at 25C [77F], 100kPa).

verify(what is:/?)

Infoboxreferences

Phosgeneis thechemical compoundwith theformulaCOCl2. This colorless gas gained infamy as achemical weaponduringWorld War Iwhere it was responsible forabout 85%of the 100,000 deaths caused by chemical weapons. It is also a valued industrial reagent and building block insynthesisof pharmaceuticals and otherorganic compounds. In low concentrations, its odor resembles freshly cut hay or grass.[5]In addition to its industrial production, small amounts occur naturally from the breakdown and thecombustionoforganochlorine compounds, such as those used inrefrigerationsystems.[6]The chemical was named by combining the Greek words 'phos' (meaning light) and genesis (birth); it does not mean it contains anyphosphorus(cf.phosphine).Contents 1Structure and basic properties 2Production 2.1Adventitious occurrence 3Uses 3.1Synthesis of carbonates 3.2Synthesis of isocyanates 3.3Laboratory uses 4Other chemistry 5History 5.1Chemical warfare 6Safety 7See also 8References 9External links

Structure and basic properties[edit]Phosgene is a planar molecule as predicted byVSEPR theory. The C=O distance is 1.18, the CCl distance is 1.74 and the ClCCl angle is 111.8.[7]It is one of the simplestacid chlorides, being formally derived fromcarbonic acid.Production[edit]Industrially, phosgene is produced by passing purifiedcarbon monoxideandchlorinegas through a bed of porousactivated carbon, which serves as acatalyst:[6]CO + Cl2 COCl2(Hrxn= 107.6kJ/mol)The reaction is exothermic, therefore the reactor must be cooled. Typically, the reaction is conducted between 50 and 150C. Above 200C, phosgene reverts to carbon monoxide and chlorine, Keq(300K) = 0.05. World production of this compound was estimated to be 2.74 million tonnes in 1989.[6]Because of safety issues, phosgene is often produced and consumed within the same plant, and extraordinary measures are made to contain this toxic gas. It is listed onschedule 3of theChemical Weapons Convention: All production sites manufacturing more than 30 tonnes per year must be declared to theOPCW.[8]Although less dangerous than many otherchemical weapons, such assarin, phosgene is still regarded as a viablechemical warfare agentbecause it is so easy to manufacture when compared to the production requirements of more technically advanced chemical weapons such as the first-generationnerve agenttabun.[9]Adventitious occurrence[edit]Uponultraviolet(UV) radiation in the presence ofoxygen,chloroformslowly converts into phosgene by aradical reaction. To suppress thisphotodegradation, 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 ofarc weldingprocesses.[10]Phosgene may also be produced during testing for leaks of older-style refrigerant gases.Chloromethanes(R12,R22and others) were formerly leak-tested in situ by employing a small gas torch (propane,butaneorpropylenegas) 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.[citation needed]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 afreonleak, or fighting fires usinghalonor halotron.[citation needed]Uses[edit]The great majority of phosgene is used in the production ofisocyanates, the most important beingtoluene diisocyanate(TDI) andmethylene diphenyl diisocyanate(MDI). These two isocyanates are precursors topolyurethanes.Synthesis of carbonates[edit]Significant amounts are also used in the production ofpolycarbonatesby its reaction withbisphenol A.[6]Polycarbonatesare an important class of engineeringthermoplasticfound, for example, in lenses in eyeglasses.Diolsreact with phosgene to give either linear or cyclic carbonates (R = H, alkyl, aryl):HOCR2-X-CR2OH + COCl2 1/n [OCR2-X-CR2OC(O)-]n+ 2 HClSynthesis of isocyanates[edit]The synthesis ofisocyanatesfrom amines illustrates theelectrophiliccharacter of this reagent and its use in introducing the equivalent of "CO2+":[11]RNH2+ COCl2 RN=C=O + 2 HCl (R =alkyl,aryl)Such reactions are conducted in the presence of a base such aspyridinethat absorbs thehydrogen chloride.Laboratory uses[edit]In the research laboratory phosgene still finds limited use inorganic 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.[12]Aside from the above reactions that are widely practiced industrially, phosgene is also used to produceacid chloridesandcarbon dioxidefromcarboxylic acids:RCO2H + COCl2 RC(O)Cl + HCl + CO2Such acid chlorides react with amines and alcohols to give, respectively, amides and esters, which are commonly used intermediates.Thionyl chlorideis more commonly and more safely employed for this application. A specific application for phosgene is the production of chloroformic esters:ROH + COCl2 ROC(O)Cl + HClPhosgene is stored in metal cylinders. The outlet is always standared, a tapered thread that is known as CGA 160Other chemistry[edit]Although it is somewhat hydrophobic, phosgene reacts withwaterto releasehydrogen chlorideandcarbon dioxide:COCl2+ H2O CO2+ 2 HClAnalogously, with ammonia, one obtainsurea:COCl2+ 4 NH3 CO(NH2)2+ 2 NH4ClHalide exchange withnitrogen trifluorideandaluminium tribromidegivesCOF2andCOBr2, respectively.[6]History[edit]Phosgene was synthesized by theBritishchemistJohn Davy(17901868) in 1812 by exposing a mixture of carbon monoxide and chlorine tosunlight. He named it "phosgene" in reference of the use of light to promote the reaction; fromGreek,phos(light) andgene(born).[13]It gradually became important in the chemical industry as the 19th century progressed, particularly in dye manufacturing.Chemical warfare[edit]Further information:Use of poison gas in World War IandSecond Italo-Abyssinian WarFollowing the extensive use of phosgene gas in combat duringWorld War I, it was stockpiled by various countries as part of their secret chemical weapons programs.[14][15][16]In May 1928, eleven tons of phosgene escaped from a war surplus store in central Hamburg.[17]300 people were poisoned of whom 10 died.[17]

US Army phosgene identification poster fromWorld War IIPhosgene was then only frequently used by theImperial Japanese Armyagainst the Chinese during theSecond Sino-Japanese War.[18]Gas weapons, such as phosgene, were produced byUnit 731and authorized by specific orders given by Hirohito (Emperor Showa) himself, transmitted by thechief of staff of the army. For example, the Emperor authorized the use of toxic gas on 375 separate occasions during theBattle of Wuhanfrom August to October 1938.[19]Safety[edit]Phosgene is an insidious poison as the odor may not be noticed and symptoms may be slow to appear.[20]Theodor detection thresholdfor phosgene is 0.4 ppm, four times thethreshold limit value. Its hightoxicityarises from the action of the phosgene on theproteinsin the pulmonaryalveoli, the site of gas exchange: their damage disrupts theblood-air barrier, causing suffocation. It reacts with theaminesof the proteins, causing crosslinking by formation ofurea-like linkages, in accord with the reactions discussed above. Phosgene detection badges are worn by those at risk of exposure.[6]Sodium bicarbonatemay be used to neutralise liquid spills of phosgene. Gaseous spills may be mitigated withammonia.[21]See also[edit] Diphosgene Triphosgene Bhopal disaster Carbonyl fluoride Carbonyl bromide FormaldehydeReferences[edit]1. Jump up^Merck Index, 11th Edition,7310.2. ^Jump up to:abcde"NIOSH Pocket Guide to Chemical Hazards #0504".National Institute for Occupational Safety and Health(NIOSH).3. Jump up^http://www.inchem.org/documents/icsc/icsc/eics0007.htm4. Jump up^"Phosgene".Immediately Dangerous to Life and Health.National Institute for Occupational Safety and Health(NIOSH).5. Jump up^CBRNE - Lung-Damaging Agents, PhosgeneMay 27, 20096. ^Jump up to:abcdefWolfgang Schneider; Werner Diller (2005), "Phosgene",Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH,doi:10.1002/14356007.a19_4117. Jump up^Nakata, M.; Kohata, K.; Fukuyama, T.; Kuchitsu, K. (1980). "Molecular Structure of Phosgene as Studied by Gas Electron Diffraction and Microwave Spectroscopy. The rzStructure and Isotope Effect".Journal of Molecular Spectroscopy83: 105117.doi:10.1016/0022-2852(80)90314-8.8. Jump up^Annex on Implementation and Verification ("Verification Annex")9. Jump up^https://itportal.decc.gov.uk/cwc_files/S2AAD_guidance.pdf10. Jump up^"Common Cleaners Can Turn Into Poison Gas".American Iron Magazine. TAM Communications. Retrieved14 October2011.11. Jump up^R. L. Shriner, W. H. Horne, and R. F. B. Cox (1943)."p-Nitrophenyl Isocyanate".Org. Synth.;Coll. Vol.2, p.45312. Jump up^Hamley, P. "Phosgene"Encyclopedia of Reagents for Organic Synthesis, 2001 John Wiley, New York.doi:10.1002/047084289X.rp14913. Jump up^John Davy (1812). "On a Gaseous Compound of Carbonic Oxide and Chlorine".Philosophical Transactions of the Royal Society of London102: 144151.doi:10.1098/rstl.1812.0008.JSTOR107310.14. Jump up^Base's phantom war reveals its secrets,Lithgow Mercury, 7/08/200815. Jump up^Chemical warfare left its legacy,Lithgow Mercury, 9/09/200816. Jump up^Chemical bombs sit metres from Lithgow families for 60 years,The Daily Telegraph, September 22, 200817. ^Jump up to:abRyan, T.Anthony (1996).Phosgene and Related Carbonyl Halides. Elsevier. pp.154155.ISBN0444824456.18. Jump up^Yuki Tanaka, "Poison Gas, the Story Japan Would Like to Forget",Bulletin of the Atomic Scientists, October 1988, p. 161719. Jump up^Y. Yoshimi and S. Matsuno,Dokugasusen Kankei Shiry II, Kaisetsu, Jugonen Sens Gokuhi Shiryoshu, 1997, p. 272920. Jump up^Borak J., Diller W. F. (2001). "Phosgene exposure: mechanisms of injury and treatment strategies".Journal of Occupational and Environmental Medicine43(2): 1109.doi:10.1097/00043764-200102000-00008.PMID11227628.21. Jump up^"Phosgene: Health and Safety Guide".International Programme on Chemical Safety. 1998.External links[edit] Davy's account of his discovery of phosgene International Chemical Safety Card 0007 CDC - Phosgene - NIOSH Workplace Safety and Health Topic NIOSH Pocket Guide to Chemical Hazards U.S. CDC Emergency Preparedness & Response U.S. EPA Acute Exposure Guideline Levels Regime For Schedule 3 Chemicals And Facilities Related To Such Chemicals, OPCW website CBWInfo website Use of Phosgene in WWII and in modern-day warfare(Refer to Section 4.C of the article) An experience with accidental poisoning by heated tetrachlorethylene solvent

http://en.wikipedia.org/wiki/Phosgene