The correct decreasing order of basic strength of following amines in aqueous medium is.

(A) $(C_2H_5)_3N$
(B) $(C_2H_5)_2NH$
(C) $C_2H_5NH_2$
(D) $NH_3$

Choose the correct answer from the options given below:

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

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

The decreasing order of basic strength of the given amines in aqueous medium is:
(C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂ > NH₃

In aqueous medium, basic strength depends on:

1. +I (electron-donating) effect of alkyl groups

2. Solvation of the conjugate acid (RNH₃⁺, R₂NH₂⁺, R₃NH⁺)

1. Secondary amine → (C₂H₅)₂NH

• Strong +I effect (two ethyl groups)

• Good solvation of protonated form
   Most basic

2. Tertiary amine → (C₂H₅)₃N

• Strong +I effect (three ethyl groups)

• But poor solvation due to steric hindrance
   Less basic than secondary

3. Primary amine → C₂H₅NH₂

• Moderate +I effect

• Good solvation
   Less basic than 2° and 3°

4. NH₃

• No +I effect
   Least basic

So the correct answer is  (B), (A), (C), (D)

(C₂H₅)₂NH > (C₂H₅)₃N > C₂H₅NH₂ > NH₃