Acetyl chloride

Acetyl chloride[1]
Names
Preferred IUPAC name
Acetyl chloride[2]
Systematic IUPAC name
Ethanoyl chloride
Other names
Acyl chloride
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.000.787
EC Number 200-865-6
RTECS number AO6390000
UNII
UN number 1717
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
-38.9·10−6 cm3/mol
Structure
2.45 D
Hazards
GHS pictograms
GHS signal word Danger
H225, H302, H314, H318, H335, H402, H412
P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P273, P280, P301+312, P301+330+331, P303+361+353, P304+340, P305+351+338, P310, P312, P321, P330, P363, P370+378, P403+233
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., gasolineHealth code 3: Short exposure could cause serious temporary or residual injury. E.g., chlorine gasReactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorusSpecial 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 was first prepared in 1852 by French chemist Charles Gerhardt by treating potassium acetate with phosphoryl chloride.[3]

The reaction of acetic anhydride with hydrogen chloride produces a mixture of acetyl chloride and acetic acid:[4]

(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, 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.

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.[7]

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. ↑ See:
  4. ↑ 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
  5. 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.
  6. ↑ US 4352761
  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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