108-24-7

A clear colorless liquid with a strong odor of vinegar. Flash point 129°F. Corrosive to metals and tissue. Density 9.0 lb /gal. Used to make fibers, plastics, pharmaceuticals, dyes, and explosives.

ACETIC ANHYDRIDE(108-24-7) reacts violently on contact with water, steam, methanol, ethanol, glycerol and boric acid. Reaction with water is particularly dangerous in presence with mineral acids (e.g., nitric, perchloric, chromic, sulfuric acid) [Chem. Eng. News 25, 3458]. Potentially explosive reactions with oxidizing reagents such as barium peroxide, chromium trioxide, chromic acid, hypochlorous acid, nitric acid, perchloric acid, peroxyacetic acid, potassium permanganate, hydrogen peroxide. [Sax, 9th ed., 1996, p. 15]. Reacts violently with metal nitrates used as nitrating agents [Davey W. et al., Chem. & Ind., 1948, p. 814].

Flammable. Reacts violently with water to generate acetic acid . This reaction is heightened by the presence of mineral acids (nitric, perchloric, sulfuric acid, etc.) [Chem. Eng. News 25, 3458].

Liquid is volatile and causes little irritation on uncovered skin. However, causes severe burns when clothing is wet with the chemical or if it enters gloves or shoes. Causes skin and eye burns and irritation of respiratory tract. Nausea and vomiting may develop after exposure.

Acetic anhydride is used as an acetylating agent or as a solvent in the manufacture of cellulose acetate, acetanilide, aspirin, synthetic fibers, plastics, explosives, resins, perfumes, and flavorings; and it is used in the textile dyeing industry. It is widely used as a pharmaceutical intermediate and as a pesticide intermediate

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately with large amounts of water. If this chemical contacts the skin, quickly remove clothing and immediately wash area with large amounts of water. If a person breathes this chemical, move the exposed person to fresh air at once and perform (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if hearth action hasstopped. When this chemical has been swallowed, get medical attention immediately. If victim is conscious, administer water or milk. Do not induce vomiting

UN1715 Acetic anhydride, Hazard class: 8; Labels: 8-Corrosive material, 3-Flammable liquid.

Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Keep away from alkaline materials, strong bases, strong acids, oxoacids, epoxides, alcohols, chromic acid (violent reaction), amines, strong caustics; finely divided metals. Contact with water forms acetic acid and liberates a large amount of heat. Corrosive to iron, steel and other metals.

Acetic anhydride is a combustible, colorless, strongly refractive, liquid which has a strongly irritating odor.

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.
Formic anhydride is an even simpler acid anhydride, but it spontaneously decomposes, especially once removed from solution.

An esterification agent used in the preparation of modified starch and for acetylation of acetylated monoglycerides. It has a strong acetic odor.

Colorless liquid

Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an afterburner and scrubber. All federal, state, and local environmental regulations must be observed.

Colorless, very mobile liquid with a very strong, acetic acid-like odor. Experimentally determined detection and recognition odor threshold concentrations were <600 μg/m³ (<140 ppb_v) and 1.5 mg/m³ (360 ppb_v), respectively (Hellman and Small, 1974).

Reported found in watercress (Nasturtium officinale r. br.).

As indicated by its organic chemistry, Ac₂O is mainly used for acetylations leading to commercially significant materials. Its largest application is for the conversion of cellulose to cellulose acetate, which is a component of photographic film and other coated materials. Similarly it is used in the production of aspirin (acetylsalicylic acid), which is prepared by the acetylation of salicylic acid.It is also used as a wood preservative via autoclave impregnation to make a longer lasting timber.
In starch industry, acetic anydride is a common acetylation compound, used for the production of modified starches
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.

ChEBI: An cyclic carboxylic anhydride of acetic acid.

Acetic anhydride is produced by carbonylation of methyl acetate :
CH₃CO₂CH₃ + CO → (CH₃CO)₂O
This process involves the conversion of methyl acetate to methyl iodide and an acetate salt. Carbonylation of the methyl iodide in turn affords acetyl iodide, which reacts with acetate salts or acetic acid to give the product. Rhodium iodide and lithium iodide are employed as catalysts. Because acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions. In contrast, the Monsanto acetic acid process, which also involves a rhodium catalyzed carbonylation of methyl iodide, is at least partially aqueous.
To a decreasing extent, acetic anhydride is also prepared by the reaction of ethenone (ketene) with acetic acid at 45–55 °C and low pressure (0.05–0.2 bar).
H₂C= C= O + CH₃COOH → (CH₃CO)₂O (ΔH = ?63 kJ/mol)
Ketene is generated by dehydrating acetic acid at 700–750 °C in the presence of triethyl phosphate as a catalyst or (in Switzerland and the CIS) by the thermolysis of acetone at 600–700 °C in the presence of carbon disulfide as a catalyst.
CH₃COOH H2C= C= O + H₂O (ΔH = +147 kJ/mol)
CH₃COCH₃ → H2C= C= O + CH₄
The route from acetic acid to acetic anhydride via ketene was developed by Wacker Chemie in 1922, when the demand for acetic anhydride increased due to the production of cellulose acetate.
Due to its low cost, acetic anhydride is purchased, not prepared, for use in research laboratories.

introduction of acetyl groups to organic substrates . In these conversions, acetic anhydride is viewed as a source of CH3CO+. Alcohols and amines are readily acetylated. 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 to function as catalyst. In specialized applications, Lewis acidic scandium salts have also proven effective catalysts.
Aromatic rings are acetylated, usually in the presence of an acid catalyst. Illustrative is the conversion of benzene to aceto phenone:
(CH3CO)₂O + C₆H₆ → CH₃COC₆H₅ + CH₃CO₂H
Ferrocene can be acetylated as well:
Cp₂Fe + (CH₃CO)₂O → CpFe(C₅H₄COCH₃).

Detection: 490 ppb; Recognition: 1.5 ppm

Synthetic Communications, 3, p. 63, 1973 DOI: 10.1080/00397917308062006
Tetrahedron Letters, 27, p. 4937, 1986 DOI: 10.1016/S0040-4039(00)85101-1

Flammable

Reactivity with Water: Reacts slowly with water, but considerable heat is liberated when contacted with spray water; Reactivity with Common Materials: Corrodes iron, steel and other metals; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Dilute with water and use sodium bicarbonate solution to rinse; Polymerization: Not pertinent; Inhibitor of Polymerization: Not pertinent.

It may be synthesized from diacetyl by partial reduction with zinc and acid or may be derived from fermentation

Chemical/Physical. Slowly dissolves in water forming acetic acid. In ethanol, ethyl acetate is formed (Windholz et al., 1983).

Adequate purification can usually be achieved by fractional distillation through an efficient column. Acetic acid can be removed by prior refluxing with CaC2 or with coarse Mg filings at 80-90o for 5days, or by distillation from a large excess of quinoline (1% AcOH in quinoline) at 75mm pressure. Acetic anhydride can also be dried by standing with Na wire for up to a week, removing the Na and distilling it under vacuum. (Na reacts vigorously with acetic anhydride at 65-70o). Dippy & Evans [J Org Chem 15 451 1950] let the anhydride (500g) stand over P2O5 (50g) for 3hours, then decanted it and stood it with ignited K2CO3 for a further 3hours. The supernatant liquid was distilled and the fraction b 136-138o was further dried with P2O5 for 12hours, followed by shaking with ignited K2CO3, before two further distillations through a five-section Young and Thomas fractionating column. The final material distilled at 137.8-138.0o. It can also be purified by azeotropic distillation with toluene: the azeotrope boils at 100.6o. After removal of the remaining toluene, the anhydride is distilled [sample had a specific conductivity of 5 x 10-9 ohm-1cm -1]. [Beilstein 2 H 96, 2 I 39, 2 II 91, 2 III 134, 2 IV 94.] Rapid procedure: Shake with P2O5, separate, shake with dry K2CO3 and fractionally distil.