|Jmol-3D images||Image 1|
|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|
|Solubility in water||Reacts|
|Refractive index (nD)||1.429|
|GHS hazard statements||H314, H331|
|GHS precautionary statements||P261, P280, P305+351+338, P310|
|EU classification||not listed|
|R-phrases||R14 R23 R29 R34 |
|S-phrases||(S1/2) S26 S30 S36/37/39 S38 S45 S61 |
|Main hazards||Toxic, corrosive, lachrymator |
|Related acyl chlorides||Malonyl chloride
|Related compounds||Oxalic acid
|Except where noted otherwise, 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 diacid chloride of oxalic acid, is a useful reagent in organic synthesis. It can be prepared by treating oxalic acid with phosphorus pentachloride. There exist two isomers of this molecule, cis-oxalyl chloride and trans-oxalyl chloride; 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
2), 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.
2 + H
2O → 2 HCl + CO
2 + CO
Applications in organic synthesis
Oxidation of alcohols
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.
Synthesis of acid chlorides
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. 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 arenes
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 in water to form the corresponding carboxylic acid.
Preparation of oxalate diesters
Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:
- 2 RCH2OH + (COCl)2 → RCH2OC(O)C(O)OCH2R + 2 HCl
- Oxalyl chloride MSDS
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