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Q.
The correct order of basicity is
NTA AbhyasNTA Abhyas 2022
Solution:
$CH_{3}\overset{\cdot \cdot }{N}H_{2} \, $ (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 $NH_{2}$ group.
$-NO_{2}$ group withdraws electron density from N of $-NH_{2}$ and decrease basic strength.
$CH _3 \ddot{ NH } H _2$ Most basic because $NH _2$ connected with $sp ^3 C$ while in i,ii\&iii Connected with $sp ^2 C \&$ basic strength $\propto+ M /+ I$
basic strength $\propto \frac{1}{- M } \propto \frac{1}{- I }$
$NO _2$ exert $- M$ so least basic while $- OCH _3$ 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.
