Oxalyl chloride

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Oxalyl chloride
Oxalyl chloride
Oxalyl-chloride-3D-balls.png Oxalyl-chloride-3D-vdW.png
CAS number 79-37-8 YesY
PubChem 65578
ChemSpider 59021 N
RTECS number KI2950000
Jmol-3D images Image 1
Molecular formula C2O2Cl2
Molar mass 126.93 g/mol
Appearance Colorless liquid
Density 1.4785 g/mL
Melting point −16 °C (3 °F; 257 K)
Boiling point 63 to 64 °C (145 to 147 °F; 336 to 337 K) at 1.017 bar
Solubility in water Reacts
Refractive index (nD) 1.429
MSDS External MSDS
GHS pictograms The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) [1]
GHS hazard statements H314, H331[1]
GHS precautionary statements P261, P280, P305+351+338, P310[1]
EU classification not listed
R-phrases R14 R23 R29 R34 [1]
S-phrases (S1/2) S26 S30 S36/37/39 S38 S45 S61 [1]
Main hazards Toxic, corrosive, lachrymator [1]
NFPA 704
Flammability (red): no hazard code Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g., calcium Special hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Related acyl chlorides Malonyl chloride
Succinyl chloride
Related compounds Oxalic acid
Diethyl oxalate
Oxalyl hydrazide
Cuprizon 1
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

Oxalyl chloride is a chemical compound with the formula (COCl)2. This colourless, sharp-smelling liquid, the diacid chloride of oxalic acid, is a useful reagent in organic synthesis.[2] It can be prepared by treating oxalic acid with phosphorus pentachloride.[3] There exist two isomers of this molecule, cis-oxalyl chloride and trans-oxalyl chloride;[4] it is the "trans-" isomer which is shown here.


Oxalyl chloride reacts with water giving off gaseous products only: hydrogen chloride (HCl), carbon dioxide (CO
), and carbon monoxide (CO). In this, it is quite different from other acyl chlorides which hydrolyze with formation of hydrogen chloride and the original carboxylic acid.

+ H
→ 2 HCl + CO
+ CO

Applications in organic synthesis[edit]

Oxidation of alcohols[edit]

The solution comprising DMSO and oxalyl chloride, followed by quenching with triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.[5][6][7]

Synthesis of acid chlorides[edit]

It is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acid chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent degrades in volatile side products in this application, which simplifies workup. One of the minor by-products from this reaction is a potent carcinogen.[8] Relative to thionyl chloride, oxalyl chloride tends to be a milder, more selective reagent. It is also more expensive than thionyl chloride so it tends to be used on a smaller scale.

Oxalyl chloride DMF catalyst.png

This reaction involves conversion of DMF to the imidoyl chloride derivative (Me2N=CHCl+), akin to the first stage in the Vilsmeier–Haack reaction. The imidoyl chloride is the active chlorinating agent.

Formylation of arenes[edit]

Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation.[9][10] The resulting acyl chloride can be hydrolysed in water to form the corresponding carboxylic acid.

Preparation of oxalate diesters[edit]

Like other acyl 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.


Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketone (C4O6), an oxide of carbon.[11]


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.[12]

See also[edit]


  1. ^ a b c d e f Oxalyl chloride MSDS
  2. ^ Salmon, R. (2001). "Oxalyl Chloride". Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.ro015. 
  3. ^ DE patent 2840435, Vogel, A.; Steffan, G.; Mannes, K.; Trescher, V., "Process for the preparation of oxalyl chloride", issued 1980-03-27, assigned to Bayer 
  4. ^ http://www.chemicalbook.com/Search_EN.aspx?keyword=oxalyl%20chloride
  5. ^ Dondoni, A.; Perrone, D. (2004), "Synthesis of 1,1-Dimethyl Ethyl-(S)-4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate by Oxidation of the Alcohol", Org. Synth. ; Coll. Vol. 10: 320 
  6. ^ Bishop, R. (1998), "9-Thiabicyclo[3.3.1]nonane-2,6-dione", Org. Synth. ; Coll. Vol. 9: 692 
  7. ^ Leopold, E. J. (1990), "Selective hydroboration of a 1,3,7-triene: Homogeraniol", Org. Synth. ; Coll. Vol. 7: 258 
  8. ^ Clayden, Jonathan (2005). Organic chemistry (Reprinted (with corrections). ed.). Oxford [u.a.]: Oxford Univ. Press. p. 296. ISBN 978-0-19-850346-0. 
  9. ^ Neubert, M. E.; Fishel, D. L. (1983), "Preparation of 4-Alkyl- and 4-Halobenzoyl Chlorides: 4-Pentylbenzoyl Chloride", Org. Synth. 61: 8 ; Coll. Vol. 7: 420 
  10. ^ Sokol, P. E. (1964), "Mesitoic Acid", Org. Synth. 44: 69 ; Coll. Vol. 5: 706 
  11. ^ Strazzolini, P.; Gambi, A.; Giumanini, A. G.; Vancik, H. (1998). "The reaction between ethanedioyl (oxalyl) dihalides and Ag2C2O4: a route to Staudinger’s elusive ethanedioic (oxalic) acid anhydride". Journal of the Chemical Society, Perkin Transactions 1 1998 (16): 2553–2558. doi:10.1039/a803430c. 
  12. ^ "Firm told to pay $65 mln for ruining plane". Reuters. 2007-12-06. Retrieved 2007-12-06.