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

The basicity of the given molecules is evaluated by considering the electron-donating and electron-withdrawing impacts of substituents on the phenyl ring.

- (A): \(\text{C}_6\text{H}_4\text{NH}_2\text{O}\) (The hydroxyl group, an electron-donating substituent, enhances the basicity of the amine.)

- (B): \(\text{C}_6\text{H}_4\text{NH}_2\text{MeO}\) (The methoxy group, a potent electron-donator, further elevates the amine's basicity.)

- (C): \(\text{C}_6\text{H}_4\text{NH}_2\text{NO}_2\) (The nitro group, a strong electron-withdrawer, diminishes the amine's basicity.) 

- (D): \(\text{C}_6\text{H}_4\text{NH}_2\text{CH}_3\) (The methyl group, a weak electron-donator, exerts a less pronounced effect compared to the hydroxyl or methoxy groups.) The ranking of basic strength is dictated by the electron-donating capacity of the substituents. Consequently, the order is: \[ \text{B}>\text{A}>\text{D}>\text{C} \] The correct sequence is \( B>A>C>D \), corresponding to option (4).