a. Draw resonance contributors for the following species. Do n...

Question

a. Draw resonance contributors for the following species. Do not include structures that are so unstable that their contributions to the resonance hybrid would be negligible. Indicate which are major contributors and which are minor contributors to the resonance hybrid.
b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?
5.

b. Do any of the species have resonance contributors that all contribute equally to the resonance hybrid?

5. Resonance structures of a molecule showing major and minor contributors for organic chemistry.

Accepted Answer

Hey, everyone, let's do this problem and says, draw the significant resonance contributors for the compound given below indicate which components are major and which are minor contributors. Are there any major resonance contributors which contribute equally to the resonance hybrid? So let's review some rules are important things to keep in mind when drawing resonance forms. So first, we can start by simply drawing the Lewis structure for our compound and that will be our first resonance form. Then we know that in resonant structures, we are simply de localizing the electrons throughout the compound. So moving electrons, we only move pi electrons though or lone pairs never sigma electrons that are in a bond and never Adams, right? We're not creating ice Summer's just moving electrons and we move those electrons towards SP Adams or Sp two Atoms, Never SP three. And lastly, like we said, we're not changing our compound, not adding anything, subtracting in anything. So the total number of electrons and also the net charge does not change. Okay. So we're just shuffling things around. And the problem also asked about the major and minor resonance contributors. Are there any equal major resonance contributors. So how much structure contributes to the overall resonance form has to do with stability, right, the more stable a structure is going to be well, the electrons are going to want to hang out in that position more often. So they will have a higher contribution to the overall structure and energy of the compound. So some factors that impact the stability, our octet do the atoms have an incomplete octet, full octet which atoms hold the charges if an atom is electro negative, which we know means it will like to hold the negative charge. But in our structure is holding a positive charge that will not be very stable, right and vice versa. For less electro negative atoms, if our charges are separated far across the compound, that will also be less stable. And lastly, we want to look at our carbo cat ions. Are they less substituted that will be less stable. We know substitution is always stability, right? Substitution, stability, substitution stability. So the more substituted our carbon Kata and the more stable. So let's apply that all of this to our structure given to us here. So we're already given the Lewis structure. I'm going to add some lone pairs here just so we can see the full picture. So our oxygen in the double bond has two lone pairs, this negative oxygen will have three lone pairs, our nitrogen has no lone pairs. Alright. So we know we want to move an electron. So probably one of these lone pairs and probably towards our positive charge, right, and it has to be towards an SP or SP two adam. Well, our negative oxygen wants to be less negative because it has a negative charge and that nitrogen wants electrons. So we can move a lone pair from this oxygen towards that nitrogen forming a double bond, which means this double bond will break between the nitrogen and the oxygen giving us the following structure. So now our oxygen in the center has a negative charge, our carbon did not change our nitrogen, the number of bonds did not change. So that still has a positive charge. Alright. Any other movement we can have. Well, like we said, we want a negative to move towards a positive if we move the oxygen that will create the same residence form as the first structure. So how about this negative carbon? Right? That carbon wants to share its electrons to. So we can donate that lone pair to make a double bond between the carbon and the nitrogen breaking this double bond between the nitrogen and oxygen that we just made to give us our last resonance form where both of our oxygen's have three lone pairs and a negative charge, negative charge. And that's all the movement we can do for this one. So let's look at the stability, find out which one is major, which of them are minor structures. So they all have complete octet. So we can't compare that. But I notice that the charges are on different atoms in different structures. Oops I forgot my positive charge on the nitrogen here. So the charge on our first structure, the negative charge is on our carbon. In all the structures, we have one positive charge on nitrogen, one negative charge on oxygen, right? But then in the first two structures, the other negative charges on carbon. Whereas in the last structure that negative charges on the oxygen and we know that oxygen is more electro negative so than carbon. So that last structure is going to be the happiest most stable structure because the electro negative oxygen has its electrons. So that will be our major structure and the other two will be minor. So the answer to the second question is no, the major residents form has no equal contributors, write the minor form does but not the major form, no equal contributors, which makes be the correct answer for this problem. That's it for this one. I hope this video is helpful and thanks for watching.

Key Concepts

Resonance Structures

Major and Minor Contributors

Equal Contribution of Resonance Contributors

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