Question

Which of the following resonating structures is the most stable?

• A. Structure 1
• B. Structure 2
• C. Structure 3
• D. Structure 4

Hint:

While comparing resonance structures:
Prefer structures with complete octets
Minimise charge separation
Place negative charge on electronegative atoms
Avoid adjacent like charges

Answer 1

The Correct Option is B

The stability of resonance structures depends on the following factors: 
Minimum charge separation 
Maximum number of atoms having complete octet 
Negative charge on more electronegative atoms 
Positive charge on less electronegative atoms 

Analysis of options: 
Option (1): Contains unnecessary charge separation and a carbocation not well stabilised. 

Option (2): Has: 
Minimum charge separation 
Positive charge delocalised and stabilised by resonance 
Negative charge located on oxygen (more electronegative) Hence, it is the most stable. 

Option (3): Contains two adjacent positive charges, leading to strong electrostatic repulsion. 

Option (4): Shows excessive charge separation and a highly unstable dicationic nitrogen.