Acetyl chloride

Acetyl chloride (CH3COCl) is an acyl chloride derived from acetic acid. It belongs to the class of organic compounds called acid halides. It is a colorless, corrosive, volatile liquid. Its formula is commonly abbreviated to AcCl.

Acetyl chloride[1]
Skeletal formula of acetyl chloride
Ball-and-stick model of acetyl chloride
Names
Preferred IUPAC name
Acetyl chloride[2]
Systematic IUPAC name
Ethanoyl chloride
Other names
Acyl chloride
Identifiers
CAS Number
3D model (JSmol)
Beilstein Reference
 605303
ChEBI
ChemSpider
ECHA InfoCard 100.000.787
EC Number
  • 200-865-6
Gmelin Reference
 1611
PubChem CID
RTECS number
  • AO6390000
UNII
UN number 1717
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
Magnetic susceptibility (χ)
 -38.9·10−6 cm3/mol
Structure
Dipole moment
 2.45 D
Hazards
GHS labelling:
Pictograms
Signal word
 Danger
Hazard statements
 H225, H302, H314, H335, H412
Precautionary statements
 P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P310, P312, P321, P330, P363, P370+P378, P403+P233, P403+P235, P405, P501
NFPA 704 (fire diamond)
3
3
2
Flash point 4 °C (39 °F; 277 K)
Autoignition
temperature
 390 °C (734 °F; 663 K)
Explosive limits 7.3–19%
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).
Y verify (what is YN ?)
Infobox references
Not to be confused with Chloroacetic acid, Chloroacetyl chloride, Acetylcholine, or Actinium(III) chloride.

Synthesis

On an industrial scale, the reaction of acetic anhydride with hydrogen chloride produces a mixture of acetyl chloride and acetic acid:[3]

(CH3CO)2O + HCl → CH3COCl + CH3CO2H

Laboratory routes

Acetyl chloride was first prepared in 1852 by French chemist Charles Gerhardt by treating potassium acetate with phosphoryl chloride.[4]


Acetyl chloride is produced in the laboratory by the reaction of acetic acid with chlorodehydrating agents such as PCl3, PCl5, SO2Cl2, phosgene, or SOCl2. However, these methods usually give acetyl chloride contaminated by phosphorus or sulfur impurities, which may interfere with the organic reactions.[5]

Other methods

When heated, a mixture of dichloroacetyl chloride and acetic acid gives acetyl chloride.[5] It can also be synthesized from the catalytic carbonylation of methyl chloride.[6] It also arises from the reaction of acetic acid, acetonitrile, 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 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, for example the reaction with ethanol to produce ethyl acetate and hydrogen chloride:

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.[7]

See also
  • Acetic acid
  • Acetyl bromide
  • Acetyl fluoride
  • Acetyl iodide

References
  1. Merck Index, 11th Edition, 79.
  2. Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. pp. 796–797. doi:10.1039/9781849733069-FP001. ISBN 978-0-85404-182-4.
  3. Cheung, Hosea; Tanke, Robin S.; Torrence, G. Paul (2000). "Acetic Acid". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a01_045.
  4. See:
  5. Leo A. Paquette (2005). "Acetyl chloride". Handbook of Reagents for Organic Synthesis, Activating Agents and Protective Groups. John Wiley & Sons. p. 16. ISBN 978-0-471-97927-2.
  6. US 4352761, Erpenbach, Heinz; Gehrmann, Klaus & Lork, Winfried et al., "Production of acetyl chloride", published 1982-10-05, assigned to Hoechst AG
  7. Charles Merritt, Jr and Charles E. Braun "9-Acetylanthracene" Org. Synth. 1950, 30, 2. doi:10.15227/orgsyn.030.0001
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