Laboratory Synthesis of Acetic Anhydride

[Ranof]

Laboratory Synthesis of Acetic Anhydride from Acetyl Chloride and Sodium Acetate
Overall Reaction:

𝐶𝐻3𝐶𝑂𝐶𝑙+𝐶𝐻3𝐶𝑂𝑂𝑁𝑎→(𝐶𝐻3𝐶𝑂)2𝑂+𝑁𝑎𝐶𝑙CH3

COCl+CH3COONa→(CH3CO) 2O+NaCl
Materials and Reagents:
Acetyl chloride: 1 mol

Anhydrous sodium acetate: 1 mol

Dry dichloromethane or benzene (as solvent, if needed)

Ice for cooling

Reaction Conditions:
Controlled temperature (0–5°C initially, then up to room temperature)

Magnetic stirring

Dry environment (to avoid hydrolysis of acetyl chloride)

Procedure:
In a clean, dry Erlenmeyer flask, mix anhydrous sodium acetate with a small amount of dry solvent (if using), and stir well.

Place the flask in an ice bath to maintain the temperature between 0–5°C.

Slowly add acetyl chloride dropwise to the cold mixture to prevent excessive heat generation.

After the addition is complete, stir the reaction mixture at room temperature for 30 to 60 minutes.

Filter the reaction mixture to remove the precipitated sodium chloride.

Remove the solvent (if used) by distillation under reduced pressure.

Purify the crude acetic anhydride by fractional distillation under vacuum.

Yield and Purity:
Typical yield: 80–90%

Final purity: >95% after distillation



Synthesis of Acetic Anhydride from Acetic Acid and Acetyl Chloride
Overall Reaction:

𝐶𝐻3𝐶𝑂𝑂𝐻+𝐶𝐻3𝐶𝑂𝐶𝑙→(𝐶𝐻3𝐶𝑂)2𝑂+𝐻𝐶𝑙

CH3COOH+CH3COCl→(CH3CO)2O+HCl

Procedure Overview:
This reaction involves treating acetic acid with acetyl chloride to produce acetic anhydride and hydrogen chloride as a by-product. It is a straightforward and high-yielding method commonly used in laboratories.

Materials:
Acetic acid (glacial): 1 mol

Acetyl chloride: 1 mol

Pyridine (optional, as an acid scavenger)

Ice bath

Dry reaction vessel

Reaction Conditions:
Temperature: 0–5°C initially, then room temperature

Stirring: Continuous magnetic stirring

Environment: Dry (to prevent hydrolysis of acetyl chloride)

Steps:
In a dry flask, add the required amount of glacial acetic acid.

Place the flask in an ice bath to maintain the temperature around 0–5°C.

Slowly add acetyl chloride dropwise while stirring to control the exothermic reaction.

Optionally, add a few drops of pyridine to neutralize the HCl generated.

After the addition, allow the mixture to stir at room temperature for 30–60 minutes.

Remove any excess reagent and by-products under reduced pressure.

Purify the resulting acetic anhydride by vacuum distillation if needed.

Yield and Purity:
Typical yield: 85–95%

Purity: >95% after distillation