Amines · Question 3

For the reaction sequence given below, the correct statement(s) is(are) [figure]

1. Both X and Y are oxygen containing compounds.
2. Y on heating with CHCl3/KOH forms isocyanide.
3. Z reacts with Hinsberg’s reagent.
4. Z is an aromatic primary amine.

Answer

(1) Both X and Y are oxygen containing compounds., (3) Z reacts with Hinsberg’s reagent.

Solution

Gabriel phthalimide synthesis.

Hot acidic KMnO4 oxidises both benzylic CH2 groups (the saturated ring is cleaved) → phthalic acid; with NH3 and heat (–2H2O) → phthalamide (X):

[figure] KMnO4, H+, [figure] NH3, , -2H2O [figure] (X)

Strong heating of X cyclises it (–NH3) to phthalimide; ethanolic KOH removes the acidic N–H → potassium phthalimide; SN2 on R–Br → N-alkylphthalimide (Y):

[figure] Strong heating, -NH3 [figure] Ethanolic KOH [figure]

R-Br [figure] (Y)

Alkaline hydrolysis of Y gives sodium phthalate (the aromatic compound) and the primary amine (Z):

[figure] NaOH [figure] + R-NH2 (Z)

(A) True: X and Y both contain C=O groups (oxygen-containing).

(B) False: Y has no free –NH2 group, so no carbylamine (isocyanide) test.

(C) True: Z is a 1° amine and reacts with Hinsberg’s reagent (C6H5SO2Cl).

(D) False: Z is an aliphatic amine (aryl halides do not undergo SN2, so Gabriel synthesis cannot give aryl amines).

Answer: (A), (C)