Question

For each of the following anions, draw all possible resonance contributors. Show the conversion between resonance contributors by including curved arrow formalism. 1. O2N Based on the resonance structures you drew in question 1, which compound (A or B) would you expect to be the more stable anion? Briefly explain your choice. 2. Looking at the compound you chose in part 2, which of its resonance contributors is the major contributor? Briefly explain. 3.

Answer 1

Generally, more the resonating structures of the anion, more will be the stable.

Hence stability is directly proportional to the number of resonating structures.

The resonating structure of A will be formed 4, and there is no conjugation of pi-bond or negative charge to nitro or carbonyl groups, and fourth one is formed very unstable.

But the resonating structure of B, will be 4, and there is negative charge is conjugated with carbonyl group therefore limit of resonance increases(extant of conjugation).

Hence stability of B is more than A.

For B, I is more contributor in resonance, due to more delocalization takes place through carbonyl group.