Among the following, the least stable resonance structure is :

Options

A.
B.
C.
D.

Answer

C

Explanation

Structure `(3)` is the least stable resonance structure because like charges `(+ve)` are carried by the adjacent atoms. Repulsion between them lands to increase of energy. Structure `(4)` is not the acceptable resonating structure as `N` atom has more than `8e^(-)` in its valence shell which is not possible. structure `(1)` is the most stable beacuse it has a conjugated system.