Oxalyl chloride
Encyclopedia
Oxalyl chloride or ethanedioyl dichloride 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.
for the preparation of acid chlorides from the corresponding carboxylic acid
s. Like thionyl chloride
, the reagent produces volatile side products in this application:
Oxalyl chloride tends to be a milder, more selective reagent
. A small amount of N,N-dimethylformamide is usually added as a catalyst for the reaction.
to give the corresponding acid chloride in a process known as a Friedel-Crafts acylation. The resulting acid chloride can be hydrolysed in water to form the corresponding carboxylic acid
.
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, and triethylamine
converts alcohols to the corresponding aldehyde
s and ketone
s via the process known as the Swern oxidation
.
(C4O6), a novel oxide of carbon
.
s, oxalyl chloride reacts with water liberating HCl
gas. Overall, its effects are comparable to those of phosgene
.
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.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
(COCl)2. This colourless, sharp-smelling liquid, the diacid chloride of oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...
, is a useful reagent in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
. It can be prepared by treating oxalic acid
Oxalic acid
Oxalic acid is an organic compound with the formula H2C2O4. This colourless solid is a dicarboxylic acid. In terms of acid strength, it is about 3,000 times stronger than acetic acid. Oxalic acid is a reducing agent and its conjugate base, known as oxalate , is a chelating agent for metal cations...
with phosphorus pentachloride.
Synthesis of acid chlorides
It is mainly used in organic synthesisOrganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
for the preparation of acid chlorides from the corresponding carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
s. Like thionyl chloride
Thionyl chloride
Thionyl chloride is an inorganic compound with the formula SOCl2. It is a reactive chemical reagent used in chlorination reactions. It is a colorless, distillable liquid at room temperature and pressure that decomposes above 140 °C. Thionyl chloride is sometimes confused with sulfuryl...
, the reagent produces volatile side products in this application:
- RCO2H + (COCl)2 → RC(O)Cl + HCl + COCarbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
+ CO2Carbon dioxideCarbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
Oxalyl chloride tends to be a milder, more selective reagent
Reagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
. A small amount of N,N-dimethylformamide is usually added as a catalyst for the reaction.
Formylation of arenes
Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chlorideAluminium chloride
Aluminium chloride is the main compound of aluminium and chlorine. It is white, but samples are often contaminated with iron trichloride, giving it a yellow colour. The solid has a low melting and boiling point. It is mainly produced and consumed in the production of aluminium metal, but large...
to give the corresponding acid chloride in a process known as a Friedel-Crafts acylation. The resulting acid chloride can be hydrolysed in water to form the corresponding carboxylic acid
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
.
Preparation of diesters
Like other acid 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
Pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula C5H5N. It is structurally related to benzene, with one C-H group replaced by a nitrogen atom...
. The diester derived from phenol
Phenol
Phenol, also known as carbolic acid, phenic acid, is an organic compound with the chemical formula C6H5OH. It is a white crystalline solid. The molecule consists of a phenyl , bonded to a hydroxyl group. It is produced on a large scale as a precursor to many materials and useful compounds...
, phenyl oxalate ester
Phenyl oxalate ester
Diphenyl oxalate is a solid ester whose oxidation products are responsible for the chemiluminescence in a glowstick. It can be synthesized by fully esterifying phenol with oxalic acid...
, is Cyalume, the active ingredient in glow sticks.
Oxidation of alcohols
The combination of DMSODimethyl sulfoxide
Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...
, oxalyl chloride, and triethylamine
Triethylamine
Triethylamine is the chemical compound with the formula N3, commonly abbreviated Et3N. It is also abbreviated TEA, yet this abbreviation must be used carefully to avoid confusion with triethanolamine, for which TEA is also a common abbreviation....
converts alcohols to the corresponding aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s and ketone
Ketone
In organic chemistry, a ketone is an organic compound with the structure RCR', where R and R' can be a variety of atoms and groups of atoms. It features a carbonyl group bonded to two other carbon atoms. Many ketones are known and many are of great importance in industry and in biology...
s via the process known as the Swern oxidation
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 and an organic base, such as triethylamine...
.
Other
Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketoneDioxane tetraketone
Dioxane tetraketone is an organic compound with the formula C4O6. It is an oxide of carbon , which can be viewed as the fourfold ketone of dioxane...
(C4O6), a novel oxide of carbon
Oxocarbon
An oxocarbon or oxide of carbon is an inorganic compound consisting only of carbon and oxygen.The simplest and most common oxocarbons are carbon monoxide and carbon dioxide...
.
Precautions
As with all acyl chlorideAcyl chloride
In organic chemistry, an acyl chloride is an organic compound with the functional group -CO-Cl. Their formula is usually written RCOCl, where R is a side chain. They are usually considered to be reactive derivatives of carboxylic acids. A specific example of an acyl chloride is acetyl chloride,...
s, oxalyl chloride reacts with water liberating HCl
Hydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
gas. Overall, its effects are comparable to those of phosgene
Phosgene
Phosgene is the chemical compound with the formula COCl2. This colorless gas gained infamy as a chemical weapon during World War I. It is also a valued industrial reagent and building block in synthesis of pharmaceuticals and other organic compounds. In low concentrations, its odor resembles...
.
In March 2000, a Malaysia Airlines
Malaysia Airlines
Malaysian Airline System Berhad , DBA Malaysia Airlines , is the government-owned flag carrier of Malaysia. Malaysia Airlines operates flights from its home base, Kuala Lumpur International Airport, and its eastern hub in Kota Kinabalu. It has its headquarters on the grounds of Sultan Abdul Aziz...
Airbus A330
Airbus A330
The Airbus A330 is a wide-body twin-engine jet airliner made by Airbus, a division of EADS. Versions of the A330 have a range of and can accommodate up to 335 passengers in a two-class layout or carry of cargo....
was damaged beyond repair after a falsely declared cargo of oxalyl chloride leaked into the cargo bay.