Question

dipole moment of 2,3,5,6-tetramethyl-4-nitroaniline is lower than that of 4-nitroaniline. Explain​

Answer 1

Dipole moment of 2,3,5,6-tetramethyl-4-nitroaniline is lower than that of 4-nitroaniline. It can be explained as follows:

Explanation:

In 4 nitroaniline, one can see a  "net shifting of electrons" in the downward direction. This is  - dueto +M+M effect of NMe2NMeX2 and −M−M effect of −NO2−NOX2.

However in 2,3,5,6-hexamethyl-4-nitroaniline, there is a steric hindrance due to placement of molecules for which the “net shifting of electrons”  is negligible. The lone pair of NMe2NMeX2 almost remains in its place.

Hence, the dipole moment of 2,3,5,6-tetramethyl-4-nitroaniline is lower than that of 4-nitroaniline.