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|
|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|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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.
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
- 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 hard to find and it's best to make it yourself, though you better have a good ventilation if you attempt to make it.
- K2Cr2O7 + 4 NaCl + 6 H2SO4 → 2 CrO2Cl2 + 2 KHSO4 + 4 NaHSO4 + 3 H2O
A good procedure can be found here.
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 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, 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.