Acetic Anhydride

Title: Acetic Anhydride
CAS Registry Number: 108-24-7
Additional Names: Acetic oxide; acetyl oxide
Molecular Formula: C4H6O3
Molecular Weight: 102.09
Percent Composition: C 47.06%, H 5.92%, O 47.02%
Line Formula: (CH3CO)2O
Literature References: Equivalent to 117.64% acetic acid. Made formerly from sod. acetate and acetyl or sulfuryl chloride; now usually obtained from acetaldehyde or acetic acid: Faith, Keyes & Clark's Industrial Chemicals, F. A. Lowenheim, M. K. Moran, Eds. (Wiley-Interscience, New York, 4th ed., 1975) pp 16-20. Of industrial importance is also the ketene process, starting with the thermal decomposition of acetone: Schmidlin, Bergmann, Ber. 43, 2821 (1910). Toxicity study: H. F. Smyth et al., Arch. Ind. Hyg. Occup. Med. 4, 119 (1951).
Properties: Very refractive liquid; strong acetic odor. Readily combustible. Fire hazard. Flash pt 130°F. d415 1.080. mp -73°. bp 139°. nD20 1.3904. Slowly soluble in water, forming acetic acid; with alcohol forms ethyl acetate; sol in chloroform, ether. LD50 orally in rats: 1.78 g/kg (Smyth).
Melting point: mp -73°
Boiling point: bp 139°
Flash point: Flash pt 130°F
Index of refraction: nD20 1.3904
Density: d415 1.080
Toxicity data: LD50 orally in rats: 1.78 g/kg (Smyth)
CAUTION: Potential symptoms of overexposure are conjunctivitis, lacrimation, corneal edema, opacity and photophobia; nasal, pharyngeal irritation; cough, dyspnea and bronchitis; skin burns, vesiculation and sensitization dermatitis. See NIOSH Pocket Guide to Chemical Hazards (DHHS/NIOSH 97-140, 1997) p 2.
Use: Manuf acetyl compounds, cellulose acetates. As acetulizer and solvent in examining wool fat, glycerol, fatty and volatile oils, resins; detection of rosin. Widely used in organic syntheses, e.g., as dehydrating agent in nitrations, sulfonations and other reactions where removal of water is necessary.
Acetimidoquinone Acetoacetanilide Acetoacetic Acid Acetobromglucose Acetochlor

Acetic anhydride
Acetic anhydride
Acetic anhydride
Acetic anhydride electron density.PNG
CAS number 108-24-7 YesY
PubChem 7918
ChemSpider 7630 YesY
EC number 203-564-8
ChEBI CHEBI:36610 YesY
RTECS number AK1925000
Jmol-3D images Image 1
Image 2
Molecular formula C4H6O3
Molar mass 102.09 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, see text
Refractive index (nD) 1.3901
EU Index 607-008-00-9
EU classification Corrosive (C)
R-phrases R10, R20/22, R34
S-phrases (S1/2), S26, S36/37/39, S45
NFPA 704
NFPA 704.svg
Flash point 49 °C; 120 °F; 322 K
Autoignition temperature 316 °C; 601 °F; 589 K
Explosive limits 2.7–10.3%
Related compounds
Related acid anhydrides Propionic anhydride
Related compounds Acetic acid
Acetyl chloride
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

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