Question

Arrange the following.

Increasing order of basic strength C₆H₅NH₂, C₆H₅N(CH₃)₂, (C₂H₅)₂NH and CH₃NH₂.

Answer 1

Due to the delocalization of the lone pair of electrons of the N-atom over the benzene ring, all aromatic amines are less basic than alkylamines i.e., CH₃NH₂. The presence of electron-donating groups (– CH₃) on the N-atom increases the basicity of substituted aniline with respect to C₆H₅NH₂.

In (C₆H₅)NH₂, the lone pair of electrons on the N-atom is delocalized over two benzene rings instead of one in C₆H₅NH₂, therefore (C₆H₅)NH₂ is much less basic than C₆H₅NH₂. Combining all the three trends together, the basic strength of the four amines increasing in order.

(C₆H₅)NH₂ < (C₂H₅)₂NH < C₆H₅N(CH₃)₂ < CH₃NH₂