Acetyl chloride

Acetyl chloride[1]
Names
IUPAC name
Acetyl chloride
Systematic IUPAC name
Ethanoyl chloride
Other names
acyl chloride
Identifiers
75-36-5 YesY
ChEBI CHEBI:37580 YesY
ChemSpider 6127 YesY
Jmol 3D model Interactive image
RTECS number AO6390000
UNII QD15RNO45K YesY
Properties
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)
Reacts with water
Structure
2.45 D
Hazards
Flammable (F)
Corrosive (C)
R-phrases R11 R14 R34
S-phrases (S1/2) S9 S16 S26 S45
NFPA 704
Flammability code 3: Liquids and solids that can be ignited under almost all ambient temperature conditions. Flash point between 23 and 38 °C (73 and 100 °F). E.g., gasoline) Health code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
3
3
2
Flash point 4 °C (39 °F; 277 K)
390 °C (734 °F; 663 K)
Explosive limits 7.3–19%
Related compounds
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:[2]

(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.[3] 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.[3] It can also be synthesized from the catalytic carbonylation of methyl chloride.[4]

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.[5]

References

  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. 1 2 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, 2. doi:10.15227/orgsyn.030.0001

External links

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