Chromyl chloride

Chromyl chloride

Names
Preferred IUPAC name Chromium(VI) dichloride dioxide
Systematic IUPAC name Dichlorodioxochromium
Other names Chromic acid chloride Chromium oxychloride Etard Reagent Chlorochromic anhydride Chromic oxychloride Chromium chloride oxide Chromium dioxide dichloride Chromium dioxychloride Chromium oxychloride
Identifiers
CAS Number	14977-61-8 Y
3D model (Jmol)	Interactive image
ChEBI	CHEBI:33038 Y
ChemSpider	21106426 Y
ECHA InfoCard	100.035.491
EC Number	239-056-8
PubChem CID	22150757
RTECS number	GB5775000
InChI InChI=1S/2ClH.Cr.2O/h2*1H;;;/q;;+2;;/p-2 Y Key: AHXGRMIPHCAXFP-UHFFFAOYSA-L Y 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
SMILES Cl[Cr](Cl)(=O)=O
Properties
Chemical formula	CrO2Cl2
Molar mass	154.9008 g/mol
Appearance	deep red fuming liquid
Odor	musty, burning, acrid
Density	1.911 g/mL, liquid
Melting point	-96.5 °C
Boiling point	117 °C
Solubility in water	Reacts
Vapor pressure	20 mmHg (20 °C)
Hazards
Main hazards	carcinogen, reacts violently with water
R-phrases (outdated)	R49 R46 R8 R35 R43 R50/53
S-phrases (outdated)	S53 S45 S60 S61
Flash point	noncombustible
US health exposure limits (NIOSH):
PEL (Permissible)	none
REL (Recommended)	Ca TWA 0.001 mg Cr(VI)/m3
IDLH (Immediate danger)	N.D.
Related compounds
Related compounds	SO2Cl2; VOCl3; MoO2Cl2; WO2Cl2; CrO2F2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Y  (what is YN ?)
Infobox references

Chromium oxychloride

Chromyl chloride is a chemical compound with the formula CrO₂Cl₂. This compound is an opaque dark blood-red liquid at room temperature and pressure. It is tetrahedral, somewhat like SO₂Cl₂. CrO₂Cl₂ is similar to the most commonly encountered chromium(VI) derivative chromate, [CrO₄]²⁻; both are tetrahedral Cr(VI) compounds. However, they differ in both oxidizing power and in physical properties: one is a liquid and the other forms salts.

CrO₂Cl₂ is a neutral molecular species. This means that in the liquid and solid forms, the individual CrO₂Cl₂ entities interact predominantly via van der Waals bonding. Such weak bonding leads to low melting and boiling points, which is related to the fact that it is a distillable liquid.

The diminished oxidizing power of [CrO₄]²⁻ vs. CrO₂Cl₂ can be ascribed to its anionic nature, which diminishes its electron affinity. Also, chloride is a poorer pi-donor ligand than is oxide.

Chromyl chloride can be prepared by mixing potassium chromate or potassium dichromate with sodium chloride and treating this mix with concentrated sulfuric acid, followed by gentle distillation.

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

CrO₂Cl₂ is highly electrophilic and an aggressive oxidizing agent, e.g. causing spontaneous combustion when dripped onto amorphous sulfur; can also oxidize toluene into benzaldehyde. Its electrophilicity is demonstrated by its rapid hydrolysis to give chromic acid and hydrochloric acid: