NEET 2025 — Chemistry solution

NEET2025Chemistry

The correct order of decreasing basic strength of the given amines is:

A
N-methylaniline > benzenamine > ethanamine > N-ethylethanamine
B
N-ethylethanamine > ethanamine > benzenamine > N-methylaniline
C
N-ethylethanamine > ethanamine > N-methylaniline > benzenamine
D
benzenamine > ethanamine > N-methylaniline > N-ethylethanamine

Solution

For aliphatic amines, more alkyl substitution increases electron density on N (in aqueous phase, with solvation, secondary > primary roughly): N-ethylethanamine ( $(C_{2} H_{5})_{2}$ NH, secondary) > ethanamine (C $_{2}$ H $_{5}$ NH $_{2}$ , primary).

Aromatic amines are weaker than aliphatic ones because the lone pair on N is delocalised into the ring. Among the two aromatic amines here, N-methylaniline has an extra +I methyl group on N, making it slightly more basic than benzenamine (aniline).

$∴$ N-ethylethanamine > ethanamine > N-methylaniline > benzenamine.

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