Chromyl chloride

Chromyl chloride

Names
Preferred IUPAC name Chromium(VI) dichloride dioxide
Systematic IUPAC name Dichlorodioxochromium
Other names Chromic oxychloride, chromium chloride oxide, chromium dioxychloride, chromium dichloride dioxide, chromium dioxide dichloride, chromium oxychloride, chlorochromic anhydride
Identifiers
Jmol-3D images	Image
SMILES Cl[Cr](Cl)(=O)=O
Properties
Chemical formula	CrO2Cl2
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 in water	Reacts
Solubility	Soluble in glacial acetic acid, benzene, carbon disulfide, carbon tetrachloride, chloroform, dichloromethane, diethyl ether, nitrobenzene, phosphorus oxychloride
Vapor pressure	20 mmHg (at 20 °C)
Hazards
Safety data sheet	Acros
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.

Properties

Chemical

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:

C₆H₅CH₃2 + 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

Physical

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.

Availability

Chromyl chloride is hard to find and it's best to make it yourself.

Preparation

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.

Projects

• Make benzaldehyde
• Spontanous ignition of sulfur

Handling

Safety

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

Storage

Chromium chloride must be stored in glass containers, 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.

Disposal

Adding a supersaturated solution of sodium sulfite or some other reducing agent will neutralize the compound to less toxic Cr(III).

References

Relevant Sciencemadness threads

• Demo with chromyl chloride