![]() ![]() So it is reasonable to move the lone pair on nitrogen away to form a π bond (keep in mind that lone pair can only form π bond, not another lone pair). The nitrogen atom has a “-” formal charge, meaning it has relatively high electron density, higher than other neutral spots. The guideline of “move electrons from the higher electron density area to the lower electron density area” provides a useful hint about where to start. Īpproach: More electrons available for movement in this example: several lone pairs and one π bond. The two resonance structures here are equivalent. Therefore it is reasonable to move the π electrons to the position beside carbocation to form another π bond, and that gives the “new” structure. There is a carbocation beside the π bond, which is the low electron density spot. Calculate the formal charge in the “new” structure and label any non-zero formal charges.Īpproach: There is only one π bond in this example, and no any lone pairs, so only the π electrons can be moved around.The “new” resonance structure should be a “product” automatically obtained by following the arrows. Use curved arrows to indicate the electron movement in the “original” resonance structure.a π bond forms the lone pair electrons and.To move electrons, only π electrons and lone pair electrons ( NEVER move σ bonds! ) can be moved from a higher electron density area to a lower electron density area by following one of the three transformations: ( Formal charges on individual atoms could be different, but net charge, which is the sum of all the charges, must be the same.) All resonance structures have the same number of electrons and net charge.All resonance structures must have the same atom connectivity and only differ in the electron arrangement.( Keep in mind that all the rules applied to Lewis structures still apply here!) ![]() All resonance structures must be valid Lewis structures.Guidelines for Drawing Resonance Structures: Some very important rules need to be followed for such purposes. Therefore, to predict whether the resonance effect applies or not, we usually need to construct “new” resonance structures (contributors) based on the “original” one available. Here, we will focus on how to draw resonance structures (or resonance contributors) for organic chemistry species and how to compare the relative stabilities between the structures.Īccording to the resonance effect, the greater the number of resonance contributors, the greater the resonance stabilization effect, and the more stable the species is. The discussion of the resonance effect heavily relies on the understanding of resonance structures. The Resonance stabilization effect (also known as the resonance effect), as briefly mentioned in Section 1.3, is one of the fundamental concepts of Organic Chemistry and has broad applications. 1.4 Resonance Structures in Organic Chemistry
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