Oxalyl chloride

Oxalyl chloride is a chemical compound with the formula (COCl)2. This colourless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.[3]

Oxalyl chloride
Oxalyl chloride
Oxalyl chloride.jpg
Preferred IUPAC name
Oxalyl dichloride[1]
Systematic IUPAC name
Ethanedioyl dichloride[1]
Other names
Oxalic acid chloride
Oxalic acid dichloride
Oxalic dichloride
Oxaloyl chloride
3D model (JSmol)
ECHA InfoCard 100.001.092 Edit this at Wikidata
EC Number
  • 201-200-2
RTECS number
  • KI2950000
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
Main hazards Toxic, corrosive, lachrymator [2]
Safety data sheet External MSDS
GHS pictograms GHS06: Toxic GHS05: Corrosive [2]
GHS Signal word Danger[2]
H314, H331[2]
P261, P280, P305+351+338, P310[2]
NFPA 704 (fire diamond)
Flammability (red): no hazard codeHealth code 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasReactivity code 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazards (white): no codeNFPA 704 four-colored diamond
Related compounds
Malonyl chloride
Succinyl chloride
Related compounds
Oxalic acid
Diethyl oxalate
Oxalyl hydrazide
Cuprizon 1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references


Oxalyl chloride was first prepared in 1892 by the French chemist Adrien Fauconnier, who reacted diethyl oxalate with phosphorus pentachloride.[4] It can also be prepared by treating oxalic acid with phosphorus pentachloride.[5]

Oxalyl chloride is produced commercially from ethylene carbonate. Photochlorination gives the tetrachloride, which is subsequently degraded:[6]

C2H4O2CO + 4 Cl2 → C2Cl4O2CO + 4 HCl
C2Cl4O2CO → C2O2Cl2 + COCl2


Oxalyl chloride reacts with water giving off gaseous products only: hydrogen chloride (HCl), carbon dioxide (CO2), and carbon monoxide (CO).

+ H
O → 2 HCl + CO
+ CO

In this, it is quite different from other acyl chlorides which hydrolyze with formation of hydrogen chloride and the original carboxylic acid.

Applications in organic synthesisEdit

Oxidation of alcoholsEdit

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.[7][8][9]

Synthesis of acyl chloridesEdit

Oxalyl chloride is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acyl chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent degrades into volatile side products in this application, which simplifies workup. One of the minor byproducts from the N,N-dimethylformamide catalyzed reaction is a potent carcinogen, stemming from the N,N-dimethylformamide decomposition.[10] 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.


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 arenesEdit

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.[11][12] The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.

Preparation of oxalate diestersEdit

Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:

OH + (COCl)
R + 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.[13]


In March 2000, a Malaysia Airlines Airbus A330-300 was damaged beyond repair after a cargo of prohibited oxalyl chloride (falsely declared as hydroxyquinoline) leaked into the cargo bay.[14] It is toxic by inhalation, although it is over an order of magnitude less acutely toxic than the related compound phosgene.[15]

See alsoEdit


  1. ^ a b Nomenclature of Organic Chemistry: IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 797. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  2. ^ a b c d e Oxalyl chloride MSDS
  3. ^ Salmon, R. (2001). "Oxalyl Chloride". Encyclopedia of Reagents for Organic Synthesis, 8 Volume Set. Encyclopedia of Reagents for Organic Synthesis. New York: John Wiley & Sons. doi:10.1002/047084289X.ro015. ISBN 0471936235.
  4. ^ Fauconnier, Adrien (1892). "Action du perchlorure de phosphore sur l'oxalate d'éthyle" [The action of phosphorus pentachloride on diethyl oxalate]. Comptes rendus hebdomadaires des séances de l'Académie des Sciences (in French). 114: 122–123.
  5. ^ 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 
  6. ^ Pfoertner, Karl-Heinz (2000). "Photochemistry". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_573.
  7. ^ Dondoni, A.; Perrone, D. (2004). "Synthesis of 1,1-Dimethyl Ethyl-(S)-4-formyl-2,2-dimethyl-3-oxazolidinecarboxylate by Oxidation of the Alcohol". Organic Syntheses.CS1 maint: multiple names: authors list (link); Collective Volume, 10, p. 320
  8. ^ Bishop, R. (1998). "9-Thiabicyclo[3.3.1]nonane-2,6-dione". Organic Syntheses.; Collective Volume, 9, p. 692
  9. ^ Leopold, E. J. (1990). "Selective hydroboration of a 1,3,7-triene: Homogeraniol". Organic Syntheses.; Collective Volume, 7, p. 258
  10. ^ Clayden, Jonathan (2005). Organic chemistry (Reprinted (with corrections) ed.). Oxford [u.a.]: Oxford Univ. Press. pp. 296. ISBN 978-0-19-850346-0.
  11. ^ Neubert, M. E.; Fishel, D. L. (1983). "Preparation of 4-Alkyl- and 4-Halobenzoyl Chlorides: 4-Pentylbenzoyl Chloride". Organic Syntheses. 61: 8.CS1 maint: multiple names: authors list (link); Collective Volume, 7, p. 420
  12. ^ Sokol, P. E. (1964). "Mesitoic Acid". Organic Syntheses. 44: 69.; Collective Volume, 5, p. 706
  13. ^ 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.
  14. ^ "Firm told to pay $65 mln for ruining plane". Reuters. 2007-12-06. Retrieved 2007-12-06.
  15. ^ Barbee, S.J.; Stone, J.J.; Hilaski, R.J. (January 1995). "Acute Inhalation Toxicology of Oxalyl Chloride". American Industrial Hygiene Association Journal. 56 (1): 74–76. doi:10.1080/15428119591017358. ISSN 0002-8894.