Chromyl chloride

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Chromyl chloride
Chromyl chloride by NileRed.jpg
Chromyl chloride fuming in air
Preferred IUPAC name
Chromium(VI) dichloride dioxide
Systematic IUPAC name
Other names
Chromic oxychloride, chromium chloride oxide, chromium dioxychloride, chromium dichloride dioxide, chromium dioxide dichloride, chromium oxychloride, chlorochromic anhydride
Molar mass 154.9008 g/mol
Appearance Viscous fuming blood-red liquid
Odor Acrid, burning
Density 1.96 g/cm3 (at 20 °C)
Melting point −96.5 °C (−141.7 °F; 176.7 K)
Boiling point 117 °C (243 °F; 390 K)
Solubility Reacts with alcohols, toluene
Soluble in glacial acetic acid, benzene, carbon disulfide, carbon tetrachloride, chloroform, dichloromethane, diethyl ether, nitrobenzene, phosphoryl chloride
Vapor pressure 20 mmHg (at 20 °C)
Safety data sheet Acros
Flash point Non-flammable
Related compounds
Related compounds
Chromic acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Chromyl chloride is an inorganic chemical compound, used as an oxidizing agent, mostly in organic chemistry. It is an opaque dark blood-red liquid at standard conditions.



Chromyl chloride will oxidize toluene to benzaldehyde. This reaction occurs in two steps:

First, a chromium compound is formed from the chromyl chloride and toluene:

C6H5CH3 + 2 CrO2Cl2 → C6H5CH[CrO2Cl2]2

The complex is hydrolyzed with water to yield benzaldehyde.

C6H5CH[CrO2Cl2]2 + 2 H2O → C6H5CH=O + Cr2O3 + 4 HCl

It will react with water to yield chromic acid and hydrochloric acid. The reaction is exothermic.

CrO2Cl2 + 2 H2O → H2CrO4 + 2 HCl


Chromyl chloride is a deep red viscous liquid, which fumes in air. It reacts with water, alcohols, but soluble in chlorinated carbons and carboxylic acids.


Chromyl chloride is difficult to find and due to its hazards, it's difficult to acquire in most countries. It's best to make it yourself, though you better have a good ventilation if you attempt to make it, as it's a nasty thing.


Chromyl chloride can be made by reacting potassium dichromate with sulfuric acid and sodium chloride:

K2Cr2O7 + 4 NaCl + 6 H2SO4 → 2 CrO2Cl2 + 2 KHSO4 + 4 NaHSO4 + 3 H2O

A good procedure can be found here.

Chromium trioxide or potassium chromate can also be used instead of potassium dichromate.




Chromyl chloride is extremely corrosive and will fume in contact with air, releasing a mist of hydrochloric and chromic acids. Proper protection must be worn when handling the compound. As it is a Cr(VI) compound, it is also carcinogenic.


Chromyl chloride must be stored in glass containers, with a proper label and a hazard symbol, away from any moisture or organic compounds. A round bottom flask with a glass stopper can be used. Inspect it periodically to make sure there's no leak and check if the ground joint froze.


To safely neutralize chromyl chloride, add the compound in a chilled inert solvent, like chloroform or glacial acetic acid and stir the suspension/solution. Slowly add a reducing agent, such as sodium sulfite/metabisulfite/thiosulfate, ascorbic acid or glucose/sugar until the color changes from red/orange to green. Try to avoid adding aqueous solutions if possible, especially if you're using glacial acetic acid as solvent, as the neutralization will generate heat.

Do this outside or in a fumehood, wearing proper protection.


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