Question

The correct order of basic strength of the following molecules is:
(A) \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\)
(B) \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\)
(C) \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\)
(D) \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\)

• A. A$ >$ B $>$ C $>$ D
• B. B $>$ C $>$ D $>$ A
• C. D $>$ B $>$ A $>$ C
• D. B $>$ A $>$ C $>$ D

Hint:

When determining the basic strength of amines in aromatic compounds, consider the electron-donating or electron-withdrawing nature of substituents. Electron-donating groups increase basicity, while electron-withdrawing groups decrease basicity.

Answer 1

The Correct Option is D

To determine the basic strength of the given molecules, we need to consider the electron-donating and electron-withdrawing effects of substituents on the phenyl group. 

- (A): \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\) (Hydroxyl group is an electron-donating group, which increases the basicity of the amine group.)

 - (B): \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\) (Methoxy group is a strong electron-donating group, which further increases the basicity of the amine group.)

- (C): \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\) (Nitro group is a strong electron-withdrawing group, which decreases the basicity of the amine group.) 

- (D): \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\) (Methyl group is a weak electron-donating group, but its effect is weaker than the hydroxyl or methoxy group.) The order of basic strength is determined by the electron-donating ability of the substituent groups. Therefore, the order is: \[ \text{B}>\text{A}>\text{D}>\text{C} \] Thus, the correct order is \( B>A>C>D \), which corresponds to option (4).