Question

Arrange the following resonanting structures of formic acid on order of decreasing stability.

• A. II $>$ I $>$ III $>$ IV
• B. I $>$ III $>$ II $>$ IV
• C. III $>$ II $>$ IV $>$ I
• D. IV $>$ III $>$ I $>$ II

Answer 1

The correct option is B I $>$ III $>$ II $>$ IV

Stability of resonating structures depends on the following-

1. Number of $\pi$ bonds $\propto$ Resonance energy $\propto$ stability.
   
2. Contributing structures should be such that the negative charge resides on an electronegative element and positive charge resides on an electropositive element.
   
3. In contributing structures, like charges should not reside on atoms close to each other and unlike charges should be widely separated.
   

Hence the correct order for the resonating structure is-

$I>III>II>IV$