Question

The decreasing order of basic strength of amines in aqueous medium is:

• A. \( {CH}_3{NH}_2>{(CH}_3{)}_2{NH}>{(CH}_3{)}_3{N}>{NH}_3 \)
• B. \( {(CH}_3{)}_2{NH}>{CH}_3{NH}_2>{(CH}_3{)}_3{N}>{NH}_3 \)
• C. \( {CH}_3{NH}_2>{(CH}_3{)}_3{N}>{(CH}_3{)}_2{NH}>{NH}_3 \)
• D. \( {(CH}_3{)}_2{NH}>{NH}_3>{(CH}_3{)}_3{N}>{CH}_3{NH}_2 \)
• E. \( {NH}_3>{CH}_3{NH}_2>{(CH}_3{)}_3{N}>{(CH}_3{)}_2{NH} \)

Hint:

In aqueous medium, basicity of amines is influenced by the electron-donating ability of alkyl groups. More alkyl groups on the nitrogen increase the basicity.

Answer 1

The Correct Option is B

Step 1: Basic strength of amines is determined by the electron-donating ability of the substituents attached to the nitrogen atom. 
Step 2: As the number of methyl groups increases, the electron-donating ability increases, making the amine more basic. 
Thus, \( {(CH}_3{)}_2{NH} \) is the most basic. 
Step 3: The order of basic strength is \( {(CH}_3{)}_2{NH}>{CH}_3{NH}_2>{(CH}_3{)}_3{N}>{NH}_3 \).