JEE Main 2015 — Amines Question with Solution

$\mathrm{C}{\mathrm{H}}_3\ddot{\mathrm{N}}{\mathrm{H}}_2\mathrm{ }$ (Aliphatic amines) Most basic due to +I effect of methyl group. Methoxy group is electron donating group and increase electron density by (+M) effect on $\mathrm{N}{\mathrm{H}}_2$ group.



$-\mathrm{N}{\mathrm{O}}_2$ group withdraws electron density from N of $-\mathrm{N}{\mathrm{H}}_2$ and decrease basic strength.


 

$\mathrm{C}{\mathrm{H}}_3\ddot{\mathrm{N}}{\mathrm{H}}_2\mathrm{ }$ Most basic because NH₂ connected with sp³ C while in i,ii&iii Connected with sp² C & basic strength $\propto$ +M/+I

basic strength $\propto$ $\frac{1}{-\text{M}}\propto \frac{1}{-\text{I}}$

NO₂ exert -M so least basic while -OCH₃ exert +M so more basic.



M effect is a stronger effect than the I effect.

Aliphatic amines are more basic than aromatic amines because in aliphatic amines lone pair of electrons on nitrogen is localized and easy to donate, while in aromatic amines lone pair of electrons on nitrogen atom is delocalized and participate in resonance.