When finding the stability order of resonationg structures of certain molecules.. there is some confusion since some structures satisfy certain factors and others satisfy certain other factors. I want to know which factor has more weight to it i.e.. which factor matters the most. Can someone give me a priority order of the factors?

Here are some I know.. Please let me know if I missed any.

  • More covalent bonds
  • Octet config and less formal charge
  • Less charge seperation
  • Negative charge on electronegative atoms
  • More stable carbocations.

To know which resonance form contributes more you can follow the following priority 1)Contributing structures in which octet rule is exceeded for second row elements make no contribution. 2)As long as the octet rule it is not exceeded for second row elements the contributing structure with greater number of covalent bonds contributes more to the resonance hybrid , maximizing the number of bonds and satisfying the octet rule normally go hand in hand. 3) when two or more structural satisfy the octet rule the major contributor is the one with the smallest separation of oppositely charged atoms. 4) among structural formulas that satisfy the the above rule and in which one or more atoms be a formal charge the major contributor is the one in which the negative charge precise on the most electronegative atom.

  • $\begingroup$ for stuctural formulas that satisfy 4) too , should we check for the stability of carbocation/anion? $\endgroup$
    – LOHO
    Feb 3 at 20:05
  • $\begingroup$ @LOHO Yes, we can check for that further $\endgroup$
    – Rover
    Mar 11 at 6:44

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