Acetyl chloride

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Acetyl chloride[1]
Skeletal formula of acetyl chloride Ball-and-stick model of acetyl chloride
Space-filling model of acetyl chloride
Acetyl chloride 25ml.jpg
Identifiers
CAS number 75-36-5 YesY
ChemSpider 6127 YesY
UNII QD15RNO45K YesY
ChEBI CHEBI:37580 YesY
RTECS number AO6390000
Jmol-3D images Image 1
Properties
Molecular 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
Hazards
EU classification Flammable (F)
Corrosive (C)
R-phrases R11 R14 R34
S-phrases (S1/2) S9 S16 S26 S45
Flash point 4 °C (39 °F; 277 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 noted otherwise, 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[edit]

Acetyl chloride mixed with acetic acid is produced by the reaction of acetic anhydride with hydrogen chloride:[2]

(CH3CO)2O + HCl → CH3COCl + CH3CO2H

Laboratory route[edit]

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.[3] HCl impurities can be removed by distilling the crude product from dimethylaniline or by degassing the mixture by a stream of argon.

Other methods[edit]

When heated, a mixture of dichloroacetic acid and acetic acid gives acetyl chloride.[3] It can also be synthesized from the catalytic carbonylation of methyl chloride.[4]

Occurrence[edit]

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[edit]

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[edit]

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-CH3CH3-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[edit]

A second major class of acetylation reactions are the Friedel-Crafts reactions.[5]

References[edit]

  1. ^ Merck Index, 11th Edition, 79.
  2. ^ Hosea Cheung, Robin S. Tanke, G. Paul Torrence “Acetic Acid” in Ullmann's Encyclopedia of Industrial Chemistry, 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a01_045
  3. ^ a b 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. 
  4. ^ US 4352761 
  5. ^ Charles Merritt, Jr and Charles E. Braun "9-Acetylanthracene" Org. Synth. 1950, 30, 1. doi:10.15227/orgsyn.030.0001

External links[edit]