Arrange the following in the increasing order of their basicities.
(I) `p-`Toluidine
(II) `N,N-`Dimethyl-p-toluidine
(III) `p-`Nitroaniline`
(IV) Aniline.

Explanation

Electron-donating groups i.e., alkyl groups in the ring and on the N-atom increase the basicity while electron-withdrawing groups such as nitro group in the ring decrease the basicity. Thus, the basicity of the given amines increases in the order : p-nitroanilineltanilineltp-toluidineltN,N-dimethyl-p-toluidine.