Chromyl chloride is the

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as '' inorganic chemis ...

with the formula CrO₂Cl₂. It is a reddish brown compound that is a volatile liquid at room temperature, which is unusual for transition metal complexes.

Preparation

Chromyl chloride can be prepared by the reaction of potassium chromate or

potassium dichromate Potassium dichromate, , is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health ...

with

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chlorid ...

in the presence of

sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid ( Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen and hydrogen, with the molecular fo ...

, followed by distillation. :K₂Cr₂O₇ + 6 HCl → 2 CrO₂Cl₂ + 2 KCl + 3 H₂O The sulfuric acid serves as the dehydration agent. It can also be prepared directly by exposing chromium trioxide to anhydrous hydrogen chloride gas. :CrO₃ + 2 HCl ⇌ CrO₂Cl₂ + H₂O The method used to prepare chromyl chloride is the basis for a qualitative test for chloride: a sample suspected of containing chloride is heated with a mixture of potassium dichromate and concentrated sulfuric acid. If chloride is present, chromyl chloride forms as evidenced by red fumes of CrO₂Cl₂. Analogous compounds are not formed with

fluoride Fluoride (). According to this source, is a possible pronunciation in British English. is an inorganic, monatomic anion of fluorine, with the chemical formula (also written ), whose salts are typically white or colorless. Fluoride salts ty ...

bromide A bromide ion is the negatively charged form (Br−) of the element bromine, a member of the halogens group on the periodic table. Most bromides are colorless. Bromides have many practical roles, being found in anticonvulsants, flame-retardant ...

iodide An iodide ion is the ion I−. Compounds with iodine in formal oxidation state −1 are called iodides. In everyday life, iodide is most commonly encountered as a component of iodized salt, which many governments mandate. Worldwide, iodine de ...

s and

cyanide Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of ...

Reagent for oxidation of alkenes

Chromyl chloride oxidizes internal alkenes to alpha-chloroketones or related derivatives. It will also attack

benzyl In organic chemistry, benzyl is the substituent or molecular fragment possessing the structure . Benzyl features a benzene ring () attached to a methylene group () group. Nomenclature In IUPAC nomenclature, the prefix benzyl refers to a substi ...

methyl group In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in ma ...

s to give aldehydes via the

Étard reaction The Étard reaction is a chemical reaction that involves the direct oxidation of an aromatic or heterocyclic bound methyl group to an aldehyde using chromyl chloride. For example, toluene can be oxidized to benzaldehyde. It is named for the Fre ...

Dichloromethane Dichloromethane (DCM or methylene chloride, methylene bichloride) is an organochlorine compound with the formula . This colorless, volatile liquid with a chloroform-like, sweet odour is widely used as a solvent. Although it is not miscible wit ...

is a suitable solvent for these reactions.

Safety considerations

CrO₂Cl₂ decomposes violently on contact with water to release hydrochloric acid (HCl) and chromic acid (H₂CrO₄). Although not combustible, chromyl chloride is a strong oxidizer and can spontaneously ignite or explode on contact with flammable substances. In case of fire, no direct contact should be made with water. Additionally, chromyl chloride is severely corrosive and easily burns the skin and eyes, and ingestion would cause severe internal damage. Its vapours are also strongly irritating to all parts of the body. Chronic: Cr^VI can produce chromosomal aberrations and is a human

carcinogen A carcinogen is any substance, radionuclide, or radiation that promotes carcinogenesis (the formation of cancer). This may be due to the ability to damage the genome or to the disruption of cellular metabolic processes. Several radioactive sub ...

via inhalation. Frequent exposure of the skin to chromyl chloride may result in

ulceration An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...

References

External links

CDC - NIOSH Pocket Guide to Chemical Hazards - Chromyl Chloride
{{DEFAULTSORT:Chromyl Chloride Chromium(VI) compounds Chromium–halogen compounds Oxychlorides Oxidizing agents Carcinogens Chromium–oxygen compounds

Preparation

Reagent for oxidation of alkenes

Safety considerations

See also

References

External links