Arrange the following in increasing order of basic strength:

Aniline, p-methylaniline, p-nitroaniline

p-nitroaniline < aniline < p-methylaniline

Aniline is a benzene with –NH₂ group attached.

p-methylaniline is a benzene ring with –NH₂ and –CH₃ groups attached at 1 and 4 positions respectively.

p-nitroaniline is a benzene ring with –NH₂ and –NO₂ groups attached at 1 and 4 positions respectively.

-CH₃(methyl) is electron releasing(+R) in nature while –NO₂(nitro) is electron withdrawing(-R) in nature. –NH₂ is basic in nature (readily donates the lone pair of electrons present on nitrogen). Depending upon the nature of groups and their position of substitution on the ring the basicity of aniline either increase or decreases. As methyl group shows +R effect it enhances the basicity of aniline while nitro group which shows -R effect decreases the basicity of aniline.