Question:

The correct order of basicity is

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Electron-donating groups raise and electron-withdrawing groups lower aniline basicity; aliphatic methylamine is more basic than any aniline.
Updated On: Nov 11, 2026
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The Correct Option is C

Solution and Explanation

The options compare aniline, p-methoxyaniline, p-nitroaniline and methylamine.
\(\mathrm{CH_3NH_2}\): the lone pair on N is not delocalised and is pushed by the +I effect of methyl, so it is the strongest base.
In anilines the lone pair is delocalised into the ring, reducing basicity. p-Methoxy (+R) increases electron density on N, so p-anisidine is more basic than aniline (\(pK_b\) about 8.7 vs 9.4).
p-Nitro (-R, -I) withdraws electron density strongly, so p-nitroaniline is the weakest base (\(pK_b\) about 13).
Order: p-nitroaniline \(\lt\) aniline \(\lt\) p-methoxyaniline \(\lt\) \(\mathrm{CH_3NH_2}\), which is option (3).
Answer: (3) p-nitroaniline < aniline < p-methoxyaniline < CH3NH2
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