Organic Chemistry: Rules for Resonance Structures

Organic chemistry makes me believe that there is a God. Even within the same structure, there’s many possibilities of other structures. I don’t care how they’ve explained it. The overlaps between p orbitals is simply divine.

Ironically, it’s also one the first topics to trip me out. Why you may ask?

Defining what a conjugate molecule was and where the hell you’re supposed to put the electron pair, that’s why.

A conjugated molecule is any molecule that has a series of three (3) or more overlapping p orbitals on adjacent atoms. (Commonly on C=C and triple bonds next to each other.)

Now that we know that, what do we do with the electrons?

Rules for Resonance structures

  1. When drawing resonance structures, the nuclei of atoms may not be moved; only pi and non-bonding electrons in conjugated p orbitals can.
  2. Each resonance structure must have the same number of electrons and the same total charge.
  3. The relative stability of resonance structures can be judged on: octet rule, the number and location of formal charges, and the interaction between charges in the structure.
  4. The actual structure most looks like the most stable resonance structure.
  5. The resonance stabilization energy increases as the number of important resonance structures increases.


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