Oxalyl chloride

Oxalyl chloride
IUPAC name	Oxalyl dichloride
Other names	Ethanedioyl dichloride Oxalic acid chloride Oxalic acid dichloride Oxalyl dichloride Oxalic dichloride Oxaloyl chloride
Identifiers
CAS number	79-37-8 Y
RTECS number	KI2950000
SMILES	ClC(=O)C(=O)Cl
Properties
Molecular formula	C2O2Cl2
Molar mass	126.93 g/mol
Appearance	colorless liquid
Density	1.4785 g/mL, liquid
Melting point	−16 °C
Boiling point	63–64 °C (1.017 bar)
Solubility in water	Decomposes
Refractive index (nD)	1.429
Hazards
MSDS	External MSDS
EU classification	not listed
NFPA 704	0 3 1
Related compounds
Related acyl chlorides	Malonyl chloride Succinyl chloride phosgene
Related compounds	Oxalic acid Diethyl oxalate Oxamide Oxalyl hydrazide Cuprizon 1
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Oxalyl chloride or ethanedioyl dichloride 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]

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. A small amount of N,N-dimethylformamide is usually added as a catalyst for the reaction.

Formylation of arenes

Oxalyl chloride reacts with aromatic compounds in the presence of aluminium 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, oxalyl chloride and triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.

Other

Oxalyl chloride was reportedly used in the first syhthesis of dioxane tetraketone (C₄O₆), a novel oxide of carbon.^[5]

Precautions

As with all acyl chlorides, oxalyl chloride reacts with water liberating HCl gas. Overall, its effects are comparable to those of phosgene.

In March 2000 a Malaysia Airlines Airbus A330 was damaged beyond repair after a falsely declared cargo of oxalyl chloride leaked into the cargo bay. ^[6]

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. (1990), "Preparation of 4-Alkyl- and 4-Halobenzoyl Chlorides: 4-Pentylbenzoyl Chloride", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv7p0420 ; Coll. Vol. 7: 420 
4. ^ Sokol, P. E. (1973), "Mesitoic Acid", Org. Synth., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV5P0706 ; Coll. Vol. 5: 706 
5. ^ Paolo Strazzolini, Alberto Gambi, Angelo G. Giumanini and Hrvoj Vancik (1998). "The reaction between ethanedioyl (oxalyl) dihalides and Ag₂C₂O₄: a route to Staudinger’s elusive ethanedioic (oxalic) acid anhydride". J. Chem. Soc., Perkin Trans. 1 (16): 2553-2558. doi:10.1039/a803430c. 
6. ^ "Firm told to pay $65 mln for ruining plane". Reuters. 2007-12-06. http://www.reuters.com/article/oddlyEnoughNews/idUSN0620441720071206. Retrieved 2007-12-06.