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:
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → (B), (A), (C), (D)
In water the basic strength of an amine depends on the inductive effect of the alkyl groups, the solvation of its ammonium ion by hydrogen bonding and steric hindrance.
The secondary amine, with two electron-releasing groups and one N–H for solvation, is the strongest. The tertiary amine comes next: its three ethyl groups give a strong inductive effect but poor solvation. Every amine is stronger than ammonia.
Shortcut: Diethylamine is the strongest and ammonia the weakest, so the order starts with (B) and ends with (D); Options (1) and (3) remain. With ethyl groups, triethylamine is stronger than ethylamine, so (A) comes before (C): Option (1).
NCERT (2026-27 edition):
Basic Character of Amines – “… Therefore, the change of nature of the alkyl group, e.g., from –CH3 to –C2H5 results in change of the order of basic strength. … The order of basic strength in case of methyl substituted amines and ethyl substituted amines in aqueous solution is as follows:
(C2H5)2NH > (C2H5)3N > C2H5NH2 > NH3”