Chromyl chloride
{{Chembox
| Watchedfields = changed
| verifiedrevid = 443523900
| ImageFileL1 = Chromyl-chloride-2D.svg
| ImageClassL1 = skin-invert-image
| ImageNameL1 = Wireframe model of chromyl chloride
| ImageFileR1 = Chromyl-chloride-3D-balls.png
| ImageClassR1 = bg-transparent
| ImageNameR1 = Ball and stick model of chromyl chloride
| ImageFile2 = Chromyl chloride.jpg
| ImageName2 = Chromyl chloride in vial
| PIN = Chromium(VI) dichloride dioxide
| SystematicName = Dichloridodioxidochromium
| OtherNames = Chromic acid chloride
Chromium oxychloride
Étard reagent
Chlorochromic anhydride
Chromic oxychloride
Chromium chloride oxide
Chromium dioxide dichloride
Chromium dioxychloride
Chromium oxychloride
| Section1 = {{Chembox Identifiers
|InChI1 = 1/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2/rCl2CrO2/c1-3(2,4)5
|InChIKey1 = AHXGRMIPHCAXFP-GRYJOLFGAD
|CASNo_Ref = {{cascite|correct|??}}
|CASNo = 14977-61-8
|Gmelin = 2231
|UNII_Ref = {{fdacite|correct|FDA}}
|UNII = JQU316FZ5W
|UNNumber = 1758
|PubChem = 22150757
|ChemSpiderID = 21106426
|ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
|EINECS = 239-056-8
|RTECS = GB5775000
|ChEBI_Ref = {{ebicite|correct|EBI}}
|ChEBI = 33038
|StdInChI_Ref = {{stdinchicite|correct|chemspider}}
|StdInChI = 1S/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2
|StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
|StdInChIKey = AHXGRMIPHCAXFP-UHFFFAOYSA-L
|SMILES = Cl[Cr](Cl)(=O)=O
|InChI = 1S/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2
|InChIKey = AHXGRMIPHCAXFP-UHFFFAOYSA-L}}
| Section2 = {{Chembox Properties
|Formula = CrO2Cl2
|MolarMass = 154.9008 g/mol
|Appearance = Blood-red fuming liquid, similar to bromine
|Density = 1.911 g/mL, liquid
|MeltingPtC = -96.5
|BoilingPtC = 118.5
|Solubility = Reacts with water
|VaporPressure = 20 mmHg (20 °C)
}}
| Section3 = {{Chembox Hazards
|ExternalSDS = [https://www.sigmaaldrich.com/MSDS/MSDS/DisplayMSDSPage.do?country=US&language=en&productNumber=200042&brand=ALDRICH&PageToGoToURL=https%3A%2F%2Fwww.sigmaaldrich.com%2Fcatalog%2Fsearch%3Fterm%3DChromyl%2Bchloride%26interface%3DProduct%2520Name%26N%3D0%2B%26mode%3Dmode%2520matchpartialmax%26lang%3Den%26region%3DUS%26focus%3DproductN%3D0%2520220003048%2520219853286%2520219853269 Sigma Aldrich - Chromyl Chloride]
|GHSPictograms = {{GHS03}}{{GHS05}}{{GHS07}}{{GHS08}}{{GHS09}}
|MainHazards = Toxic, oxidizer, carcinogenic, mutagenic, reacts violently with water
|FlashPt = noncombustible
|GHSSignalWord = Danger
|HPhrases = {{H-phrases|271|314|317|340|350|410}}
|PPhrases = {{P-phrases|201|210|280|303+361+353|305+351+338+310|308+313}}{{cite web |title=Chromyl chloride 200042 |url=https://www.sigmaaldrich.com/catalog/product/aldrich/200042?lang=en®ion=GB |website=Sigma-Aldrich |archive-url=https://archive.org/download/chromyl-chloride-msds/Chromyl%20chloride%20MSDS.pdf |archive-date=2020-09-01}}
|NFPA-H = 3
|NFPA-F = 0
|NFPA-R = 2
|NFPA-S = W+OX
|PEL = none{{PGCH|0142}}
|REL = Ca TWA 0.001 mg Cr(VI)/m3
}}
| Section4 = {{Chembox Related
|OtherCompounds = Sulfuryl chloride
Vanadium oxytrichloride
Molybdenum dichloride dioxide
Tungsten dichloride dioxide
Chromyl fluoride
Uranyl chloride}}
}}
Chromyl chloride is an inorganic compound with the formula CrO2Cl2. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal compounds. It is the dichloride of chromic acid.
Preparation
Chromyl chloride can be prepared by the reaction of potassium chromate or potassium dichromate with hydrogen chloride in the presence of concentrated sulfuric acid, followed by distillation.{{cite book |last= Moody |first= B.J. |title= Comparative Inorganic Chemistry |edition= 1 |publisher= Edward Arnold |location= London |chapter= 22 |page= 381 |year= 1965 |isbn= 0-7131-3679-0 }}{{cite book|doi=10.1002/9780470132333.ch63|title=Chromyl Chloride [Chromium(VI) Dioxychloride]|series=Inorganic Syntheses|pages=205–207|volume=2|year=1946|last1=Sisler|first1=Harry H.|isbn=9780470132333}}
:K2Cr2O7 + 6 HCl → 2 CrO2Cl2 + 2 KCl + 3 H2O
The sulfuric acid serves as a dehydration agent.
It can also be prepared directly by exposing chromium trioxide to anhydrous hydrogen chloride gas.
:CrO3 + 2 HCl ⇌ CrO2Cl2 + H2O
Usage
= Test for the presence of chlorides =
The chromyl chloride test involves heating a sample suspected to contain chlorides with potassium dichromate and concentrated sulfuric acid. If a chloride is present then chromyl chloride forms which is indicated by the evolution of red smoke. No similar compound is formed in the presence of fluoride, bromide, iodide, or cyanide, making this test specific to chlorides.
=Reagent for oxidation of alkenes=
Chromyl chloride oxidizes internal alkenes to alpha-chloroketones or related derivatives.{{cite journal|title=Aldehydes by Oxidation of Terminal Olefins with Chromyl Chloride: 2,4,4-Trimethylpentanal
|first1=Fillmore|last1=Freeman|first2=Richard H.|last2=DuBois|first3=Thomas G.|last3=McLaughlin|journal=Org. Synth.|year=1971|volume=51|page=4|doi= 10.15227/orgsyn.051.0004}} It will also attack benzylic methyl groups to give aldehydes via the Étard reaction. Dichloromethane is a suitable solvent for these reactions.{{cite journal|author=F. Freeman|title=Chromyl Chloride|journal=Encyclopedia of Reagents for Organic Synthesis|year=2004|doi=10.1002/047084289X.rc177|isbn=0471936235}}
= Others =
CrO2Cl2 can also be used to test for the absence of nitrate ions.
Safety considerations
{{main|Hexavalent chromium}}
File:Chromyl chloride ampouled.png to prevent vapours leaking out of the container|234x234px]]
Chromyl chloride is severely corrosive and easily burns the skin and eyes. It is a probable human carcinogen.{{cite book |editor= Prof CH Gray |title= Laboratory Handbook of Toxic Agents |edition= 2 |publisher= Royal Institute of Chemistry |location= London |chapter= IV |page= 79 |year= 1966 }}
References
{{Commons category}}
{{reflist}}
External links
- [https://www.cdc.gov/niosh/npg/npgd0142.html CDC - NIOSH Pocket Guide to Chemical Hazards - Chromyl Chloride]
{{Chromium compounds}}
{{DEFAULTSORT:Chromyl Chloride}}
Category:Chromium(VI) compounds