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Acetic anhydride
Acetic anhydride
Acetic anhydride
Names
Preferred IUPAC name

Acetic anhydride

Systematic IUPAC name

Ethanoic anhydride

Other names

Ethanoyl ethanoate
Acetic acid anhydride
Acetyl acetate
Acetyl oxide
Acetic oxide

Identifiers

CAS Number
  • 108-24-7 check

3D model (JSmol)
  • Interactive image
  • Interactive image
ChEBI
  • CHEBI:36610 check
ChEMBL
  • ChEMBL1305819
ChemSpider
  • 7630 check
ECHA InfoCard 100.003.241 Edit this at Wikidata
EC Number
  • 203-564-8

PubChem CID
  • 7918
RTECS number
  • AK1925000
UNII
  • 2E48G1QI9Q check
UN number 1715

CompTox Dashboard (EPA)
  • DTXSID0024395 Edit this at Wikidata

InChI

  • InChI=1S/C4H6O3/c1-3(5)7-4(2)6/h1-2H3 check

    Key: WFDIJRYMOXRFFG-UHFFFAOYSA-N check

  • InChI=1/C4H6O3/c1-3(5)7-4(2)6/h1-2H3

    Key: WFDIJRYMOXRFFG-UHFFFAOYAH

SMILES

  • O=C(OC(=O)C)C

  • CC(=O)OC(=O)C

Properties

Chemical formula

 C4H6O3
Molar mass 102.089 g·mol−1
Appearance colorless liquid
Density 1.082 g cm−3, liquid
Melting point −73.1 °C (−99.6 °F; 200.1 K)
Boiling point 139.8 °C (283.6 °F; 412.9 K)

Solubility in water

 2.6 g/100 mL, reacts (see text)
Vapor pressure 4 mmHg (20 °C)[1]

Magnetic susceptibility (χ)

 -52.8·10−6 cm3/mol

Refractive index (nD)

 1.3901
Thermochemistry[2]

Std enthalpy of
formation (ΔfH⦵298)

 −624.4 kJ·mol−1
Pharmacology
Legal status
Hazards
GHS labelling:

Pictograms

 GHS02: FlammableGHS05: CorrosiveGHS07: Exclamation mark

Signal word

 Danger

Hazard statements

 H226, H302, H314, H332

Precautionary statements

 P210, P233, P240, P241, P242, P243, P260, P261, P264, P270, P271, P280, P301+P312, P301+P330+P331, P303+P361+P353, P304+P312, P304+P340, P305+P351+P338, P310, P312, P321, P330, P363, P370+P378, P403+P235, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 3: Short exposure could cause serious temporary or residual injury. E.g. chlorine gasFlammability 2: Must be moderately heated or exposed vĩ đại relatively high ambient temperature before ignition can occur. Flash point between 38 and 93 °C (100 and 200 °F). E.g. diesel fuelInstability 1: Normally stable, but can become unstable at elevated temperatures and pressures. E.g. calciumSpecial hazard W: Reacts with water in an unusual or dangerous manner. E.g. sodium, sulfuric acid

3

2

1

W

Flash point 49 °C (120 °F; 322 K)
316 °C (601 °F; 589 K)
Explosive limits 2.7–10.3%
Lethal dose or concentration (LD, LC):

LC50 (median concentration)

 1000 ppm (rat, 4 hr)[3]
NIOSH (US health exposure limits):

PEL (Permissible)

 TWA 5 ppm (20 mg/m3)[1]

REL (Recommended)

 C 5 ppm (20 mg/m3)[1]

IDLH (Immediate danger)

 200 ppm[1]
Safety data sheet (SDS) ICSC 0209
Related compounds

Related acid anhydrides

 Propionic anhydride

Related compounds

 Acetic acid
Acetyl chloride

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

Acetic anhydride, or ethanoic anhydride, is the chemical compound with the formula (CH3CO)2O. Commonly abbreviated Ac2O, it is the simplest isolable anhydride of a carboxylic acid and is widely used as a reagent in organic synthesis. It is a colorless liquid that smells strongly of acetic acid, which is formed by its reaction with moisture in the air.

Structure and properties[edit]

Acetic anhydride in a glass bottle

Acetic anhydride, lượt thích most acid anhydrides, is a flexible molecule with a nonplanar structure.[4] The pi system linkage through the central oxygen offers very weak resonance stabilization compared vĩ đại the dipole-dipole repulsion between the two carbonyl oxygens. The energy barriers vĩ đại bond rotation between each of the optimal aplanar conformations are quite low.[5]

Like most acid anhydrides, the carbonyl carbon atom of acetic anhydride has electrophilic character, as the leaving group is carboxylate. The internal asymmetry may contribute vĩ đại acetic anhydride's potent electrophilicity as the asymmetric geometry makes one side of a carbonyl carbon atom more reactive than vãn the other, and in doing sánh tends vĩ đại consolidate the electropositivity of a carbonyl carbon atom vĩ đại one side (see electron mật độ trùng lặp từ khóa diagram).

Production[edit]

Acetic anhydride was first synthesized in 1852 by the French chemist Charles Frédéric Gerhardt (1816-1856) by heating potassium acetate with benzoyl chloride.[6]

Acetic anhydride is produced by carbonylation of methyl acetate:[7]

CH3CO2CH3 + CO → (CH3CO)2O

The Tennessee Eastman acetic anhydride process involves the conversion of methyl acetate vĩ đại methyl iodide and an acetate salt. Carbonylation of the methyl iodide in turn affords acetyl iodide, which reacts with acetate salts or acetic acid vĩ đại give the product. Rhodium chloride in the presence of lithium iodide is employed as catalysts. Because acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions.

To a decreasing extent, acetic anhydride is also prepared by the reaction of ketene (ethenone) with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).[8]

H2C=C=O + CH3COOH → (CH3CO)2O
(ΔH = −63 kJ/mol)

The route from acetic acid vĩ đại acetic anhydride via ketene was developed by Wacker Chemie in 1922,[9] when the demand for acetic anhydride increased due vĩ đại the production of cellulose acetate.

Due vĩ đại its low cost, acetic anhydride is usually purchased, not prepared, for use in research laboratories.

Reactions[edit]

Acetic anhydride is a versatile reagent for acetylations, the introduction of acetyl groups vĩ đại organic substrates.[10] In these conversions, acetic anhydride is viewed as a source of CH3CO+.

Acetylation of alcohols and amines[edit]

Alcohols and amines are readily acetylated.[11] For example, the reaction of acetic anhydride with ethanol yields ethyl acetate:

(CH3CO)2O + CH3CH2OH → CH3CO2CH2CH3 + CH3COOH

Often a base such as pyridine is added vĩ đại function as catalyst. In specialized applications, Lewis acidic scandium salts have also proven effective catalysts.[12]

Acetylation of aromatic rings[edit]

Aromatic rings are acetylated by acetic anhydride. Usually acid catalysts are used vĩ đại accelerate the reaction. Illustrative are the conversions of benzene vĩ đại acetophenone[13] and ferrocene vĩ đại acetylferrocene:[14]

(C5H5)2Fe + (CH3CO)2O → (C5H5)Fe(C5H4COCH3) + CH3CO2H

Preparation of other acid anhydrides[edit]

Dicarboxylic acids are converted vĩ đại the anhydrides upon treatment with acetic anhydride.[15] It is also used for the preparation of mixed anhydrides such as that with nitric acid, acetyl nitrate.

Precursor vĩ đại geminal diacetates[edit]

Aldehydes react with acetic anhydride in the presence of an acidic catalyst vĩ đại give geminal diacetates.[16] A former industrial route vĩ đại vinyl acetate involved the intermediate ethylidene diacetate, the geminal diacetate obtained from acetaldehyde and acetic anhydride:[17]

CH3CHO + (CH3CO)2O → (CH3CO2)2CHCH3

Hydrolysis[edit]

Acetic anhydride dissolves in water vĩ đại approximately 2.6% by weight.[18] Aqueous solutions have limited stability because, lượt thích most acid anhydrides, acetic anhydride hydrolyses vĩ đại give carboxylic acids. In this case, acetic acid is formed, this reaction product being fully water miscible:[19]

(CH3CO)2O + H2O → 2 CH3COOH

Applications[edit]

As indicated by its organic chemistry, acetic anhydride is mainly used for acetylations leading vĩ đại commercially significant materials. Its largest application is for the conversion of cellulose vĩ đại cellulose acetate, which is a component of photographic film and other coated materials, and is used in the manufacture of cigarette filters. Similarly it is used in the production of aspirin (acetylsalicylic acid), which is prepared by the acetylation of salicylic acid.[20] It is also used as an active modification agent via autoclave impregnation and subsequent acetylation vĩ đại make a durable and long-lasting timber.[21]

In starch industry, acetic anhydride is a common acetylation compound, used for the production of modified starches (E1414, E1420, E1422)

Legal status[edit]

Because of its use for the synthesis of heroin by the diacetylation of morphine, acetic anhydride is listed as a U.S. DEA List II precursor, and restricted in many other countries.[22][23]

Safety[edit]

Acetic anhydride is an irritant and combustible liquid; it is highly corrosive vĩ đại skin and any direct tương tác will result in severe burns. Because of its reactivity toward water and alcohol, foam or carbon dioxide are preferred for fire suppression.[24] The vapour of acetic anhydride is harmful.[25]

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References[edit]

  1. ^ a b c d NIOSH Pocket Guide vĩ đại Chemical Hazards. "#0003". National Institute for Occupational Safety and Health (NIOSH).
  2. ^ John Rumble (June 18, 2018). CRC Handbook of Chemistry and Physics (99th ed.). CRC Press. pp. 5–3. ISBN 978-1138561632.
  3. ^ "Acetic anhydride". Immediately Dangerous vĩ đại Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  4. ^ Seidel, R. W.; Goddard, R.; Nöthling, N.; Lehmann, C. W. (2016), "Acetic anhydride at 100 K: the first crystal structure determination", Acta Crystallographica Section C, 72 (10): 753–757, doi:10.1107/S2053229616015047, PMID 27703123.
  5. ^ Wu, Guang; Van Alsenoy, C.; Geise, H. J.; Sluyts, E.; Van Der Veken, B. J.; Shishkov, I. F.; Khristenko (2000), "Acetic Anhydride in the Gas Phase, Studied by Electron Diffraction and Infrared Spectroscopy, Supplemented with ab Initio Calculations of Geometries and Force Fields", The Journal of Physical Chemistry A, 104 (7): 1576–1587, Bibcode:2000JPCA..104.1576W, doi:10.1021/jp993131z.
  6. ^ Charles Gerhardt (1852) “Recherches sur les acides organiques anhydres” (Investigations into the anhydrides of organic acids), Comptes rendus … , 34 : 755-758.
  7. ^ Zoeller, J. R.; Agreda, V. H.; Cook, S. L.; Lafferty, N. L.; Polichnowski, S. W.; Pond, D. M. (1992), "Eastman Chemical Company Acetic Anhydride Process", Catal. Today, 13 (1): 73–91, doi:10.1016/0920-5861(92)80188-S
  8. ^ Arpe, Hans-Jürgen (2007-01-11), Industrielle organische Chemie: Bedeutende vor- und Zwischenprodukte (6th ed.), Weinheim: Wiley-VCH, pp. 200–1, ISBN 978-3-527-31540-6[permanent dead link].
  9. ^ Milestones in the history of WACKER, Wacker Chemie AG, retrieved 2009-08-27.
  10. ^ "Acid Anhydrides", Understanding Chemistry, retrieved 2006-03-25.
  11. ^ Shakhashiri, Bassam Z., "Acetic Acid & Acetic Anhydride", Science is Fun…, Department of Chemistry, University of Wisconsin, archived from the original on 2006-03-03, retrieved 2006-03-25.
  12. ^ Macor, John; Sampognaro, Anthony J.; Verhoest, Patrick R.; Mack, Robert A. (2000). "(R)-(+)-2-Hydroxy-1,2,2-Triphenylethyl Acetate". Organic Syntheses. 77: 45. doi:10.15227/orgsyn.077.0045.; Collective Volume, vol. 10, p. 464
  13. ^ Roger Adams and C. R. Noller "p-Bromoacetophenone" Org. Synth. 1925, vol. 5, p. 17. doi:10.15227/orgsyn.005.0017
  14. ^ Taber, Douglass F., Column chromatography: Preparation of Acetyl Ferrocene, Department of Chemistry and Biochemistry, University of Delaware, archived from the original on 2009-05-02, retrieved 2009-08-27.
  15. ^ B. H. Nicolet and J. A. Bender "3-Nitrophthalic Anhydride" Org. Synth. 1927, vol. 7, 74. doi:10.15227/orgsyn.007.0074
  16. ^ R. T. Bertz "Furfuryl Diacetate" Org. Synth. 1953, 33, 39. doi:10.15227/orgsyn.033.0039
  17. ^ G. Roscher "Vinyl Esters" in Ullmann's Encyclopedia of Chemical Technology, 2007 John Wiley & Sons: Thủ đô New York. doi:10.1002/14356007.a27_419
  18. ^ Acetic Anhydride: Frequently Asked Questions (PDF), British Petroleum, archived from the original (PDF) on 2007-10-11, retrieved 2006-05-03.
  19. ^ Acetic Anhydride: Material Safety Data Sheet (PDF) (PDF), Celanese, archived from the original (PDF) on 2007-09-27, retrieved 2006-05-03.
  20. ^ Acetic anhydride (PDF), SIDS Initial Assessment Report, Geneva: United Nations Environment Programme, p. 5.
  21. ^ Tullo, Alexander (2012-08-06). "Making Wood Last Forever With Acetylation". Chemical and Engineering News. No. 32. American Chemical Society. ISSN 0009-2347. Retrieved 2022-09-17.
  22. ^ "§ 1310.02 - Substances Covered". e-CFR. 2022-02-15. Archived from the original on 2022-02-15.
  23. ^ UN Intercepts Taliban's Heroin Chemical in Rare Afghan Victory, Bloomberg, archived from the original on 22 October 2012, retrieved 2008-10-07.
  24. ^ "Data Sheets". International Occupational Safety and Health Information Centre. Retrieved 2006-04-13.
  25. ^ "NIOSH". Pocket Guide vĩ đại Chemical Hazards. Archived from the original on 22 April 2006. Retrieved 2006-04-13.

External links[edit]

  • ICSC 0209
  • NIOSH Pocket Guide vĩ đại Chemical Hazards