Question

The correct increasing order of basic strength for the following compounds is: 

• A. \( II<III<I \)
• B. \( III<I<II \)
• C. \( III<II<I \)
• D. \( II<I<III \)

Hint:

Electron-withdrawing groups (-NO\(_2\)) decrease basicity, while electron-donating groups (-CH\(_3\)) increase basicity in aromatic amines.

Answer 1

The Correct Option is D

Step 1: Understanding the effect of substituents on basicity.
- The basicity of aniline derivatives depends on the electron-donating or withdrawing nature of the substituents on the benzene ring.
- The amino group (-NH\(_2\)) donates electrons via resonance, increasing basicity.
Step 2: Analyzing the given compounds.
- Compound I (Aniline, \( C_6H_5NH_2 \)):
- Has no additional substituent.
- Moderate basicity due to partial lone pair delocalization.
- Compound II (p-Nitroaniline, \( C_6H_4(NO_2)NH_2 \)):
- The nitro group (-NO\(_2\)) is an electron-withdrawing group.
- Strongly reduces electron density on nitrogen, making it least basic.
- Compound III (p-Toluidine, \( C_6H_4(CH_3)NH_2 \)):
- The methyl group (-CH\(_3\)) is an electron-donating group.
- Increases electron density on nitrogen, making it the most basic.
Step 3: Arranging the compounds in increasing basicity.
\[ {p-Nitroaniline (II)<Aniline (I)<p-Toluidine (III)} \] Thus, the correct order is \( II<I<III \), matching option (D).