Oxalyl chloride is an organic

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

(COCl)₂. This colorless, sharp-smelling liquid, the di

acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...

oxalic acid Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early inve ...

, is a useful reagent in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

Preparation

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

with

phosphorus pentachloride Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moist ...

. Oxalyl chloride is produced commercially from

ethylene carbonate Ethylene carbonate (sometimes abbreviated EC) is the organic compound with the formula (CH2O)2CO. It is classified as the Cyclic compound, cyclic carbonate ester of ethylene glycol and carbonic acid. At room temperature (25 °C) ethylene car ...

. Photochlorination gives the tetrachloride, which is subsequently degraded: :C₂H₄O₂CO + 4 Cl₂ → C₂Cl₄O₂CO + 4 HCl :C₂Cl₄O₂CO → C₂O₂Cl₂ + COCl₂

Reactions

Oxalyl chloride reacts with

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

giving off gaseous products only:

hydrogen chloride The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...

(HCl),

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

(CO₂), and

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

(CO). : In this, it is quite different from other

s which hydrolyze with formation of hydrogen chloride and the original

carboxylic acid In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

Applications in organic synthesis

Oxidation of alcohols

The solution comprising

DMSO Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds an ...

and oxalyl chloride, followed by quenching with

triethylamine Triethylamine is the chemical compound with the formula N(CH2CH3)3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine or tetraethylammonium, for which TEA ...

converts

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

s to the corresponding

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl grou ...

s and

ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...

s via the process known as the

Swern oxidation The Swern oxidation, named after Daniel Swern, is a chemical reaction whereby a primary or secondary alcohol is oxidized to an aldehyde or ketone using oxalyl chloride, dimethyl sulfoxide (DMSO) and an organic base, such as triethylamine. It is one ...

Synthesis of acyl chlorides

Oxalyl chloride is mainly used together with a ''N'',''N''-dimethylformamide catalyst in

for the preparation of acyl chlorides from the corresponding

s. Like

thionyl chloride Thionyl chloride is an inorganic compound with the chemical formula . It is a moderately volatile, colourless liquid with an unpleasant acrid odour. Thionyl chloride is primarily used as a chlorinating reagent, with approximately per year bein ...

, 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 In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

. It is also more expensive than

so it tends to be used on a smaller scale. : Oxalyl chloride DMF catalyst

This reaction involves conversion of DMF to the

imidoyl chloride Imidoyl chlorides are organic compounds that contain the functional group RC(NR')Cl. A double bond exist between the R'N and the carbon centre. These compounds are analogues of acyl chloride. Imidoyl chlorides tend to be highly reactive and are m ...

derivative (Me₂N=CHCl⁺), akin to the first stage in the

Vilsmeier–Haack reaction The Vilsmeier–Haack reaction (also called the Vilsmeier reaction) is the chemical reaction of a substituted amide (1) with phosphorus oxychloride and an electron-rich arene (3) to produce an aryl aldehyde or ketone (5). The reaction is named af ...

. The imidoyl chloride is the active chlorinating agent.

Formylation of arenes

Oxalyl chloride reacts with

aromatic In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...

compounds in the presence of

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...

to give the corresponding

in a process known as a Friedel-Crafts acylation. The resulting acyl chloride can be hydrolysed to form the corresponding

Preparation of oxalate diesters

Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters: : Typically, such reactions are conducted in the presence of a base such as

pyridine Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a d ...

. The diester derived from

phenol Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it req ...

phenyl oxalate ester Diphenyl oxalate (trademark name Cyalume) is a solid whose oxidation products are responsible for the chemiluminescence in a glowstick. This chemical is the double ester of phenol with oxalic acid. Upon reaction with hydrogen peroxide, 1,2-dioxet ...

, is Cyalume, the active ingredient in

glow stick A glow stick, also known as a light stick, chem light, light wand, light rod, and rave light, is a self-contained, short-term light-source. It consists of a translucent plastic tube containing isolated substances that, when combined, make light ...

Other

Oxalyl chloride was reportedly used in the first synthesis of

dioxane tetraketone Dioxane tetraketone (or 1,4-dioxane-2,3,5,6-tetrone) is an organic compound with the formula C4O6. It is an oxide of carbon (an oxocarbon), which can be viewed as the fourfold ketone of dioxane. It can also be viewed as the cyclic dimer of oxi ...

(C₄O₆), an oxide of carbon.

Precautions

In March 2000, a

Malaysia Airlines Malaysia Airlines Berhad (MAB; ms, Penerbangan Malaysia Berhad), formerly known as Malaysian Airline System (MAS; ), and branded as Malaysia Airlines, is the flag carrier airline of Malaysia and a member of the Oneworld airline alliance. (The ...

Airbus A330 The Airbus A330 is a wide-body aircraft developed and produced by Airbus. Airbus conceived several derivatives of the A300, its first airliner in the mid-1970s. Then the company began development on the A330 twinjet in parallel with the A340 ...

-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.

References

{{Authority control Acyl chlorides Carbon oxohalides