$\mathrm{C}{\mathrm{H}}_3\ddot{\mathrm{N}}{\mathrm{H}}_2\mathrm{ }$ (Aliphatic amines) Most basic due to +I effect of methyl group. Methoxy group provides electron density (+M)- $\mathrm{N}{\mathrm{H}}_2$



$-\mathrm{N}{\mathrm{O}}_2$ group with draws electron density from N of $-\mathrm{N}{\mathrm{H}}_2$


 

$\mathrm{C}{\mathrm{H}}_3\ddot{\mathrm{N}}{\mathrm{H}}_2\mathrm{ }$ 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 effect