Question

Which of the following statements is/are correct regarding the canonical forms given below:

• A. Structure I has the lowest energy
• B. I, II and III are not canonical forms of each other
• C. The resonance hybrid is more stable than the structures I, II and III and IV
• D. The stability order is: $I>III>II>IV$

Answer 1

Answer: (A), (C), (D)

The stability order is: $I>III>II>IV$

Resonating structures having more number of covalent bonds are more stable.
So, structures I and III are supposed to be more stable than the rest. Out of these two, I will be more stable because the negative charge is present on N in I whereas in III it is present on C.
Out of II and IV, II is more stable than IV because negative charge is present on N in II whereas in IV it is present on C.
So, the order of stability can be given as:
I>III>II>IV
The resonance hybrid will be the most stable of all.