Acetyl chloride (CH
3COCl) is an
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 ...
derived from
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
. It belongs to the class of
organic compounds called
acid halides. It is a colorless, corrosive, volatile
liquid
A liquid is a nearly incompressible fluid that conforms to the shape of its container but retains a (nearly) constant volume independent of pressure. As such, it is one of the four fundamental states of matter (the others being solid, gas, a ...
. Its formula is commonly abbreviated to AcCl.
Synthesis
On an industrial scale, the reaction of
acetic anhydride
Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a col ...
with
hydrogen chloride produces a mixture of acetyl chloride and acetic acid:
:(CH
3CO)
2O + HCl → CH
3COCl + CH
3CO
2H
Laboratory routes
Acetyl chloride was first prepared in 1852 by French chemist
Charles Gerhardt by treating
potassium acetate with
phosphoryl chloride.
Acetyl chloride is produced in the laboratory by the reaction of
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
with chlorodehydrating agents such as
PCl3,
PCl5,
SO2Cl2,
phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
, or
SOCl2. However, these methods usually give acetyl chloride contaminated by phosphorus or sulfur impurities, which may interfere with the organic reactions.
Other methods
When heated, a mixture of
dichloroacetyl chloride and
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
gives acetyl chloride.
It can also be synthesized from the catalytic
carbonylation of
methyl chloride. It also arises from the reaction of acetic acid,
acetonitrile
Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...
, and
hydrogen chloride.
Occurrence
Acetyl chloride is not expected to exist in nature, because contact with
water would
hydrolyze it into acetic acid and
hydrogen chloride. In fact, if handled in open air it releases white "smoke" resulting from hydrolysis due to the moisture in the air. The smoke is actually small droplets of
hydrochloric acid and
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
formed by hydrolysis.
Uses
Acetyl chloride is used for acetylation reactions, i.e., the introduction of an acetyl group. Acetyl is an
acyl group having the formula ). For further information on the types of chemical reactions compounds such as acetyl chloride can undergo, see
acyl halide. Two major classes of acetylations include
esterification and the
Friedel-Crafts reaction.
Acetic acid esters and amide
Acetyl chloride is a reagent for the preparation of esters and amides of acetic acid, used in the
derivatization of
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 and
amines. One class of acetylation reactions are
esterification, for example the reaction with
ethanol to produce
ethyl acetate and
hydrogen chloride:
:
CH3COCl + HO-CH2-CH3 -> CH3-COO-CH2-CH3 + HCl
Frequently such acylations are carried out in the presence of a base such as
pyridine,
triethylamine, or
DMAP, which act as
catalysts to help promote the reaction and as
bases
neutralize
Neutralization may refer to:
* Neutralization (chemistry), a chemical reaction where a base and an acid react to form a salt
* Neutralisation (immunology), pathogen neutralization caused by antibodies
* Neutralisation (sociology)
* Neutralizati ...
the resulting
HCl. Such reactions will often proceed via
ketene.
Friedel-Crafts acetylations
A second major class of acetylation reactions are the
Friedel-Crafts reactions.
[Charles Merritt, Jr and Charles E. Braun "9-Acetylanthracene" Org. Synth. 1950, 30, 2. ]
See also
*
Acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main component ...
*
Acetyl bromide
*
Acetyl fluoride
Acetyl fluoride is an acyl halide with the chemical formula CH3COF. The formula is commonly abbreviated AcF.
Synthesis
Acetyl fluoride is synthesized using hydrogen fluoride and acetic anhydride. Acetic acid is produced as a byproduct.
: + ↠...
*
Acetyl iodide
References
External links
*
{{Authority control
Acyl chlorides
Reagents for organic chemistry
Organic compounds with 2 carbon atoms