Arrange the following in increasing order of basic strength in aqueous solution:

(A) $C_6H_5NH_2$
(B) $C_2H_5NH_2$
(C) $(C_2H_5)_2NH$
(D) $NH_3$

Choose the correct answer from the options given below:

(A), (D), (B), (C)

The correct answer is Option (1) → (A), (D), (B), (C)

The correct order is: C₆H₅NH₂ < NH₃ < C₂H₅NH₂ < (C₂H₅)₂NH

In aqueous solution, the increasing order of basic strength is:
Aniline < Ammonia < Ethylamine < Diethylamine

1. (A) C₆H₅NH₂ (Aniline) → Least basic

   • The lone pair on nitrogen is delocalized into the benzene ring (resonance).

   • This reduces availability of the lone pair for protonation.
     ⇒ Weakest base

2. (D) NH₃ (Ammonia)

   • No electron-donating alkyl groups.

   • Lone pair is available but not strongly pushed.
     ⇒ More basic than aniline, but less than alkyl amines.

3. (B) C₂H₅NH₂ (Primary amine)

   • +I effect of ethyl group increases electron density on nitrogen.
     ⇒ More basic than NH₃.

4. (C) (C₂H₅)₂NH (Secondary amine) → Most basic in aqueous solution

   • Stronger +I effect (two alkyl groups).

   • Also better solvation than tertiary amines, making it most basic here.