Question

Arrange the following.

In increasing order of basic strength C₆H₅NH₂, C₆H₅NHCH₃, C₆H₅NH₂, p-Cl-C₆H₄-NH₂

Answer 1

Chlorine atom has both – I effect and + R effect since – I effect out weights the + R effect, therefore p-chloro aniline is weak base than aniline. Alkyl groups are electron-donating groups.

As a result, the electron density on the nitrogen atom increases in the ethylamine, and thus they can donate lone pair of electrons more easily. Therefore Ethylamine is more base than aromatic amines.

Due to delocalization of the lone pair of electrons of the N-atom over the benzene ring, C₆H₅NH, and C₆H₅NHCH₃ are far less basic than C₂H₅NH₂. Further due to +I effect of the CH₃ group, C₆H₅NHCH₃ is a little more basic than C₆H₅NH₂. Therefore increasing order basic strength is p-Cl-C₆H₄-NH₂ < C₆H₅NH₂ < C₆H₅NHCH₃ < C₆H₅NH₂.