Introduction and preparation of Acetic

AnhydridePrepared By:

MIHIR PRAJAPATI:13BCH047

PRERAK SHAH:13BCH048

i. Molecular formula :C4H6O3. ii. Structural formula :(CH3CO)2Oiii.Molecular weight :102.09 gmol−1

iv.Freezing point :-730C(-1000F)v. Boiling Point(760mm Hg) :1380C(2820F)vi.Flash Point:52.5-530C vii.Auto-ignition Temperture:315-3310C(6290F)viii.Specific gravity:1.082-1.083(at200C)ix.Appearance: Colorless liquidx. Refractive index: 1.3901

PHYSICAL PROPERTIES

Physical Properties: The lower simple anhydrides are colorless Liquids

with a sharp pungent smell. They are insoluble in water because of the lack of

hydrogen bonding but they dissolve because of the conversion of acetic anhydride into an acid salt by hydrolysis.

They have higher boiling points than the acid from which they are derived .This is so because of their large size and enhanced van der waal’s interactions.

They are characterized by the c=o stretching band in IR spectrum at frequency range 1800-1850 and 1740-1790 cm-1.

Acetic anhydrides is a colorless liquid , 139oC ,sp gr 1.083.

It is sparingly soluble in cold water but miscible with alcohol, ether, and acetic acid.it gives reactions parallel to those cholorides, although less vigorously.

• IUPAC name:

(acetic anhydride)

Chemical Properties:• Anhydrides react with nucleophiles in the same

way as acid chlorides. But since –OCOR group is not as electronegative as Cl atom, anhydrides are less reactive than acid chlorides.

• Thus anhydrides give all the nucleophilic substitution reaction shown by acid chlorides but with less vigor.

• The compounds derived by loss of a water molecule between two molecules of a carboxylic acid are called Acid anhydrides or simply anhydrides.

• The mechanism of the nucleophilic substitution here is the same as stated for acid chlorides with the difference that the by-product is a molecule of the carboxylic acid instead of HCL.

Common name: ethanoic anhydride.

Other name: Ethanoyl ethanoate Acetic acid anhydride Acetyl acetate Acetyl oxide

PREPARATION

There are basically two methods of preparation of acetic anhydrides:-

1)By reaction of acid halide with a carboxylic acid

2)By reaction of acid halide with a salt of carboxylic acid

By reaction of acid halide with carboxylic acid

ACID ACID CHLORIDE

MIXED ANHYDRIDE

By reaction of acid halide with a salt of carboxylic acid

SODIUM SALT

ANHYDRIDE

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

1. Acetic anhydride is produced by Acetone cracking:

2. The Ketene decomposition reactions is:

3. The Acetic anhydride formation reaction is:

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).

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

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.

ProductionAcetic anhydride was first synthesized in 1852 by the French

chemist Charles Frédéric Gerhardt (1816-1856) by heating potassium acetate with benzoyl chloride.

The Tennessee Eastman acetic anhydride 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 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.

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.

Suppliers Triveni interchem Pvt.Ltd A.B enterprise Prakash chemicals Agencies Pvt.ltd Bhagawati Chemicals Iol Chemical and pharmaceuticals ltd.(Ludhiana) J.k Rangwals, Chemicals Pvt.Ltd(Mumbai) Ankit Raj Organo Chemicals Pvt.Ltd(Mumbai) MC India international (Jaipur) Organix(Mumbai) Kundan Rice mills Ltd(Mumbai)

per year India make average 8% of Acetic anhydride all over World.

Region Thousand metric Ton

Canada 70

Mexico 87

United states 1223

Western Europe 539

New research

• In the hydrosphere, Acetic anhydride is rapidly hydrolyzed (half-life 4.4 min.) to acetic acid which is readily biodegradable• In the atmosphere, it is converted to Acetic acid which is subject to photo oxidative degradation (half-life 22 days).•Toxicity to aquatic organisms is moderate (18 to 3400 mg/l), but it persists only for a short time due to its rapid hydrolysis to acetate/acetic acid. It has virtually no potential for bioaccumulation (log Kow = -0.27). The PEC/PNEC ratio is much less than 1, indicating that acetic anhydride has a low potential for risk to the environment.

Safety:Acetic anhydride is an irritant and combustible liquid. Because of

its reactivity toward water, alcohol foam or carbon dioxide are preferred for fire suppression. The vapour of acetic anhydride is harmful.

When mixed with hydrogen peroxide, an excess of acetic anhydride reacts with one of the reaction products acetic acid and forms highly shock sensitive and explosive diacetyl peroxide.

Health hazards: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.

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