Chemistry - GOC Question with Solution | TestHub

The N lone pair is conjugated with the ring on one side and with $\mathrm{C}=\mathrm{O}$ on the other, so the ring (6 C), N, the carbonyl C and O form a single system : 9 atoms. The $\mathrm{C}{\mathrm{H}}_3$ is $\mathrm{s}{\mathrm{p}}^3$ and is not conjugated.