Chromyl chloride

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Chromyl chloride
Wireframe model of chromyl chloride Chromyl-chloride-2D.svg
Wireframe model of chromyl chloride
Ball and stick model of chromyl chloride Chromyl-chloride-3D-balls.png
Ball and stick model of chromyl chloride
Chromyl chloride in vial Chromyl chloride.jpg
Chromyl chloride in vial
Names
Preferred IUPAC name
Chromium(VI) dichloride dioxide
Systematic IUPAC name
Dichloridodioxidochromium
Other names
Chromic acid chloride
Chromium oxychloride
Chromic oxychloride
Étard reagent
Chlorochromic anhydride
Chromium chloride oxide
Chromium dioxide dichloride
Chromium dioxychloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.035.491 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 239-056-8
2231
PubChem CID
RTECS number
  • GB5775000
UNII
UN number 1758
  • InChI=1S/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2 Yes check.svgY
    Key: AHXGRMIPHCAXFP-UHFFFAOYSA-L Yes check.svgY
  • InChI=1S/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2
    Key: AHXGRMIPHCAXFP-UHFFFAOYSA-L
  • InChI=1/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2/rCl2CrO2/c1-3(2,4)5
    Key: AHXGRMIPHCAXFP-GRYJOLFGAD
  • Cl[Cr](Cl)(=O)=O
Properties
CrO2Cl2
Molar mass 154.9008 g/mol
AppearanceBlood-red fuming liquid, similar to bromine
Odor Musty, burning, acrid [1]
Density 1.911 g/mL, liquid
Melting point −96.5 °C (−141.7 °F; 176.7 K)
Boiling point 118.5 °C (245.3 °F; 391.6 K)
Reacts with water
Vapor pressure 20 mmHg (20 °C) [1]
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
Toxic, oxidizer, carcinogenic, mutagenic, reacts violently with water [1]
GHS labelling:
GHS-pictogram-rondflam.svg GHS-pictogram-acid.svg GHS-pictogram-exclam.svg GHS-pictogram-silhouette.svg GHS-pictogram-pollu.svg
Danger
H271, H314, H317, H340, H350, H410
P201, P210, P280, P303+P361+P353, P305+P351+P338+P310, P308+P313 [2]
NFPA 704 (fire diamond)
NFPA 704.svgHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 0: Will not burn. E.g. waterInstability 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g. white phosphorusSpecial hazard W+OX: Reacts with water in an unusual or dangerous manner AND is oxidizer
3
0
2
W
OX
Flash point noncombustible [1]
NIOSH (US health exposure limits):
PEL (Permissible)
none [1]
REL (Recommended)
Ca TWA 0.001 mg Cr(VI)/m3 [1]
IDLH (Immediate danger)
N.D. [1]
Safety data sheet (SDS) Sigma Aldrich - Chromyl Chloride
Related compounds
Related compounds
Sulfuryl chloride
Vanadium oxytrichloride
Molybdenum dichloride dioxide
Tungsten dichloride dioxide
Chromyl fluoride
Uranyl chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

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. [3]

Contents

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. [4] [5]

K2Cr2O7 + 6 HCl → 2 CrO2Cl2 + 2 KCl + 3 H2O

The sulfuric acid serves as a dehydration agent. This reaction, the chloride test, gives a strikingly red product. It was once used as a test for chloride. No similar compound is formed in the presence of fluoride, bromide, iodide, or cyanide, making this test specific to chlorides.

It can also be prepared directly by exposing chromium trioxide to anhydrous hydrogen chloride gas.

CrO3 + 2 HCl ⇌ CrO2Cl2 + H2O

When trityl chloride is used in place of HCl, the products are CrO2Cl2 and the alkoxides CrO2Cl(OCPh3) and CrO2(OCPh3)2 (Ph = C6H5). [6]

Reactions

Chromyl chloride is a Lewis acid, and a highly aggressive oxidant. It reacts with cyclohexane to give chlorocyclohexane, chlorocyclohexanone, and other species. [7]

Chromyl chloride oxidizes internal alkenes to alpha-chloroketones or related derivatives. [8] It will also attack benzylic methyl groups to give aldehydes via the Étard reaction. Dichloromethane is a suitable solvent for these reactions. [9]

When treated with conventional Lewis bases, chromyl chloride forms adducts, such as CrO2Cl2(2,2'-bipy): [10]

CrO2Cl2 + 2 L → CrO2Cl2L2

Safety considerations

Chromyl chloride is often stored in sealed glass ampoules to prevent vapours leaking out of the container Chromyl chloride ampouled.png
Chromyl chloride is often stored in sealed glass ampoules to prevent vapours leaking out of the container

Chromyl chloride is severely corrosive and easily burns the skin and eyes. It is a probable human carcinogen. [11]

References

  1. 1 2 3 4 5 6 7 NIOSH Pocket Guide to Chemical Hazards. "#0142". National Institute for Occupational Safety and Health (NIOSH).
  2. "Chromyl chloride 200042" (PDF). Sigma-Aldrich. Archived from the original on 2020-09-01.
  3. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 1022. doi:10.1016/C2009-0-30414-6. ISBN   978-0-08-037941-8.
  4. Moody, B.J. (1965). "22". Comparative Inorganic Chemistry (1 ed.). London: Edward Arnold. p. 381. ISBN   0-7131-3679-0.
  5. Sisler, Harry H. (1946). "Chromyl Chloride [Chromium(VI) Dioxychloride]". Inorganic Syntheses. Vol. 2. pp. 205–207. doi:10.1002/9780470132333.ch63. ISBN   9780470132333.{{cite book}}: ISBN / Date incompatibility (help)
  6. Stavropoulos, Pericles; Bryson, Nathan; Youinou, Marie Therese; Osborn, John A. (1990). "Chromyl Complexes with Aryloxy and Siloxy Ligands". Inorganic Chemistry. 29 (10): 1807–1811. doi:10.1021/ic00335a009.
  7. Gunay, Ahmet; Theopold, Klaus H. (2010). "C−H Bond Activations by Metal Oxo Compounds". Chemical Reviews. 110 (2): 1060–1081. doi:10.1021/cr900269x. PMID   20143877.
  8. Freeman, Fillmore; DuBois, Richard H.; McLaughlin, Thomas G. (1971). "Aldehydes by Oxidation of Terminal Olefins with Chromyl Chloride: 2,4,4-Trimethylpentanal". Org. Synth. 51: 4. doi:10.15227/orgsyn.051.0004.
  9. F. Freeman (2004). "Chromyl Chloride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc177. ISBN   0471936235.
  10. Levason, William; Reid, Gillian; Zhang, Wenjian (2014). "Synthesis, Properties, and Structures of Chromium(VI) and Chromium(V) Complexes with Heterocyclic Nitrogen Ligands". Zeitschrift für Anorganische und Allgemeine Chemie. 640 (1): 35–39. Bibcode:2014ZAACh.640...35L. doi: 10.1002/zaac.201300482 .
  11. Prof CH Gray, ed. (1966). "IV". Laboratory Handbook of Toxic Agents (2 ed.). London: Royal Institute of Chemistry. p. 79.