Aim:
To prepare acetanilide.
Theory:
The replacement of one hydrogen atom of the — NH2 group
of aniline by CH3CO– group in the presence of glacial acetic acid. Gives
acetanilide. In the laboratory, acetylation is usually carried out with acetic
anhydride. Acetyl chloride may also be used for the purpose of acetylation if
acetic anhydride is not available. Acetylation with CH3COCl is usually carried
out in the presence of pyridine.
Material
Required:
• Funnel: One • Round bottomed flask (100 mL) : One •
Beaker (250 mL) : One • Air condenser : One • Sand bath : One • Clamp and iron
stand : One • Pumice stone : As per need • Melting point assembly : One
Chemicals:
Aniline : 5 mL • Acetic anhydride /Acetyl chloride : 5
mL • Acetic acid / Pyridine : 5 mL
Procedure:
(i) Take 5 mL of aniline in a 100 mL round bottom flask
and add acetylating mixture containing 5 mL acetic anhydride and 5 mL glacial
acetic acid. Alternatively, you can use 5 mL of acetyl chloride and 5 mL of dry
pyridine as the acctylating mixture.
(ii) Fit an air condenser on the mouth of the round
bottom flask after adding a few pumice stones and reflux the mixture gently for
10-15 minutes on a sand bath.
(iii) Cool the reaction mixture and pour it slowly in
150-200 mL of ice cold water with stirring.
(iv)Filter the solid, wash it with cold water and
recrystallise a small amount of sample from hot water containing a few drops of
methanol or ethanol.
(v) Report the yield and the melting point of the
compound.
Result
(a) Yield of acetanilide _______ g.
(b) Melting point of acetanilide is _______ °C.
