|Preferred IUPAC name
|Systematic IUPAC name
Oxalic acid chloride
Oxalic acid dichloride
3D model (JSmol)
CompTox Dashboard (EPA)
|Molar mass||126.93 g/mol|
|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|
Refractive index (nD)
|Main hazards||Toxic, corrosive, lachrymator |
|Safety data sheet||External MSDS|
|GHS signal word||Danger|
|P261, P280, P305+351+338, P310|
Related acyl chlorides
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
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. It can be prepared by treating oxalic acid with phosphorus pentachloride.
Oxalyl chloride was first prepared in 1892 by the French chemist Adrien Fauconnier, who reacted diethyl oxalate with phosphorus pentachloride.
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.
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. 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.
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. The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.
Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:
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. It is toxic by inhalation, although it is over an order of magnitude less acutely toxic than the related compound phosgene.