A) Experiment: Preparation of Acetanilide. B) Purpose: To demonstrate principles

Question

A) Experiment: Preparation of Acetanilide.
B) Purpose: To demonstrate principles of multistep synthesis, protecting groups, and Electrophilic Aromatic Substitution

1) From the figure, how was unchanged "aniline" separated from "acetanilide"?

2) What does it mean by "unchanged" aniline?

Scheme 21.2 NO NH2 NHCOCH CH COH0 CH Co,Na 0 C 7 Acetanilide Benzenc Nitrobenzene Anilinc NH2 NHCOCH NHCOCHj CiSO,H NHy (2 NaCO SO NH2 O.NH2 So C Sulfanilamide -Acctamidohenrene. sulionamide nrene- sultonyl chloride

Explanation / Answer

1)Unchanged aniline can be separated from acetanilide by crystallisation followed by suction filtration through a buchner funnel.

Acetalnilide is a solid (MP:113.50C ) ,whereas aniline (MP: -6.30C)   and acetic anhydride are liquids. Solubility of acetanilide in water is negligible . Add a small quantity of water , heat the solution in a water bath till the entire acetanilide solid dissolves and then allow to cool. Separate the solid acetanilide crystallised by filtration.

2) Unchanged aniline is the aniline which is unreacted and remains in the solution, if the % conversion is not 100%. Or if acetic anhydride is the limiting reagent (ie Aniline is in excess) unreacted aniline remains in the reaction mixture.

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