Arrange the following in increasing orde

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Target Exam

CUET

Subject

Chemistry

Chapter

Organic: Amines

Question:

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

(A) $CH_3NH_2$
(B) $C_6H_5CH_2NH_2$
(C) $C_6H_5NH_2$
(D) $(CH_3)_3N$

Choose the correct answer from the options given below:

Options:

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

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

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

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

Correct Answer:

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

Explanation:

The correct answer is Option (4) → (C), (B), (D), (A)

Compound	Type	Reason for basic strength in water	Order
(C) C₆H₅NH₂	Aromatic amine	Lone pair on N is delocalised into benzene ring → least available for protonation	1 (weakest)
(B) C₆H₅CH₂NH₂	Benzylamine	No delocalisation; sp³ N, +I effect of phenyl through –CH₂– (weaker than alkyl)	2
(D) (CH₃)₃N	Tertiary aliphatic	Strong +I effect of three methyl groups, but steric hindrance to solvation of (CH₃)₃NH⁺ ion reduces basicity below secondary	3
(A) CH₃NH₂	Primary aliphatic	Two methyl groups give good +I effect; best solvation of CH₃NH₃⁺ ion → strongest base	4 (strongest)