OXALYL CHLORIDE

Oxalyl chloride
Oxalyl chloride
General
Systematic name	Oxalyl dichloride
Other names	Ethanedioyl dichloride Oxalic acid chloride Oxalic acid dichloride Oxalyl dichloride Oxalic dichloride Oxaloyl chloride
Molecular formula	C2O2Cl2
SMILES	ClC(=O)C(=O)Cl
Molar mass	126.93 g/mol
Appearance	colorless liquid
CAS number	[79-37-8]
Properties
Density and phase	1.4785 g/mL, liquid
Solubility in water	Decomposes
Solubility	diethyl ether, benzene, chloroform carbon disulfide
Melting point	−16 °C
Boiling point	63–64 °C (1.017 bar)
Viscosity	? cP at ? °C
Thermodynamic data
Standard enthalpy offormation ɢf''H''oliquid	? kJ/mol
Standard molar entropy ''S''oliquid	? J.K−1.mol−1
'Hazards'
EU classification	not listed
NFPA 704
RTECS number	KI2950000
Supplementary data page
Structure and properties	''n'' = 1.429 ''É√r'', etc.
Thermodynamic data	Phase behaviour Solid, liquid, gas
Spectral data	UV, IR, NMR, MS
Regulatory data	Flash point, RTECS number, etc.
Related compounds
Related acyl chlorides	Malonyl chloride Succinyl chloride phosgene
Related compounds	Oxalic acid Diethyl oxalate Oxamide Oxalyl hydrazide Cuprizon 1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)

'Oxalyl chloride' is a chemical compound with the formula (COCl)₂. This colourless liquid, the diacid chloride of oxalic acid, is a useful reagent in organic synthesis.^[1] It can be prepared by treating oxalic acid with phosphorus pentachloride.^[2]

Contents

Applications in organic synthesis

Synthesis of acid chlorides

Formylation of arenes

Preparation of diesters

Oxidation of alcohols

Precautions

References

Applications in organic synthesis

Synthesis of acid chlorides

It is mainly used in organic synthesis for the preparation of acid chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent produces volatile side products in this application:
:RCO₂H + (COCl)₂ → RC(O)Cl + HCl + CO + CO₂
Oxalyl chloride tends to be a milder, more selective reagent.

Formylation of arenes

Oxalyl chloride reacts with aromatic compounds in the presence of aluminum chloride to give the corresponding acid chloride in a process known as a Friedel-Crafts acylation.^[3][4] The resulting acid chloride can be hydrolysed in water to form the corresponding carboxylic acid.

Preparation of diesters

Like other acid chlorides, oxalyl chloride reacts with alcohols to give esters:
:2 RCH₂OH + (COCl)₂ → RCH₂OC(O)C(O)OCH₂R + 2 HCl
Typically such reactions are conducted in the presence of a base such as pyridine. The diester derived from phenol, phenyl oxalate ester, is Cyalume, the active ingredient in glow sticks.

Oxidation of alcohols

The combination of DMSO and oxalyl chloride converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.

Precautions

Oxalyl chloride reacts with water liberating HCl gas. Overall, its effects are comparable to those of phosgene. See MSDS:
http://ptcl.chem.ox.ac.uk/MSDS/OX/oxalyl_chloride.html

http://www.sciencelab.com/xMSDS-Oxalyl_chloride-9926352

http://www.jtbaker.com/msds/englishhtml/o6180.htm

References

1. Salmon, R. "Oxalyl Chloride" in Encyclopedia of Reagents for Organic Synthesis 2001, John Wiley & Sons, New York.DOI: 10.1002/047084289X.ro015
2. Vogel, A.; Steffan, G.; Mannes, K.; Trescher, V. "Oxalyl chloride" DE 78-2840435 19780916.Chemical Abstracts Number 93:94818
3. Neubert, M. E.; Fishel, D. L. ''Organic Syntheses'', Collected Volume 7, p.420 (1990). http://www.orgsyn.org/orgsyn/pdfs/CV7P0420.pdf
4. Sokol, P. E. "Mesitoic Acid" Organic Syntheses, Collected Volume 5, p.706 (1973). http://www.orgsyn.org/orgsyn/pdfs/CV5P0706.pdf