Acetyl chloride

Acetyl chloride

Names
IUPAC name Acetyl chloride
Systematic IUPAC name Ethanoyl chloride
Other names acyl chloride
Identifiers
CAS Number	75-36-5 Y
ChEBI	CHEBI:37580 Y
ChemSpider	6127 Y
Jmol 3D model	Interactive image
RTECS number	AO6390000
UNII	QD15RNO45K Y
InChI InChI=1S/C2H3ClO/c1-2(3)4/h1H3 Y Key: WETWJCDKMRHUPV-UHFFFAOYSA-N Y InChI=1/C2H3ClO/c1-2(3)4/h1H3 Key: WETWJCDKMRHUPV-UHFFFAOYAQ
SMILES ClC(=O)C
Properties
Chemical formula	CH3COCl
Molar mass	78.49 g/mol
Appearance	colorless liquid
Density	1.104 g/ml, liquid
Melting point	−112 °C (−170 °F; 161 K)
Boiling point	52 °C (126 °F; 325 K)
Solubility in water	Reacts with water
Structure
Dipole moment	2.45 D
Vapor pressure	{{{value}}}
Related compounds
Related acyl chlorides	Propionyl chloride Butyryl chloride
Related compounds	Acetic acid Acetic anhydride Acetyl bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Acetyl chloride, CH₃COCl is an acid chloride derived from acetic acid. It belongs to the class of organic compounds called acyl halides. It is a colorless, corrosive, volatile liquid.

Synthesis

Acetyl chloride mixed with acetic acid is produced by the reaction of acetic anhydride with hydrogen chloride:

(CH₃CO)₂O + HCl → CH₃COCl + CH₃CO₂H

Laboratory route

Acetyl chloride is produced in the laboratory by the reaction of acetic acid with chlorodehydrating agents such as PCl₃, PCl₅, SO₂Cl₂, or SOCl₂. However, these methods usually gives acetyl chloride contaminated by phosphorus or sulfur impurities, which may interfere with the organic reactions. a route avoiding these impurities of phosphorus and sulphur is that of phosgene and acetic acid, COCl₂ + CH₃COOH = CH₃COCl + HCl + CO₂. HCl impurities can be removed by distilling the crude product from dimethylaniline or by degassing the mixture by a stream of argon.

Other methods

When heated, a mixture of dichloroacetic acid and acetic acid gives acetyl chloride. It can also be synthesized from the catalytic carbonylation of methyl 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 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-C(=O)-CH₃. 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 alcohols and amines. One class of acetylation reactions are esterification.

CH₃COCl + HO-CH₂-CH₃ → CH₃-COO-CH₂-CH₃ + H-Cl

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 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.

External links

• International Chemical Safety Card 0210