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Solution: Draw resonance structures for each of the following:...

Question

Draw resonance structures for each of the following:

Video Transcript

Alright guys, let's take a look at our compound. Now, I'm going to go ahead and just paste it in and notice that I didn't include where the bonds are, so let's go ahead and do that, we have a bond right here, right? With the positive charge here, we have a bond here and the bond right here and I'm just going to change this charge to make it stand out, let's make it to color red like that. Now I'm missing some lone pairs on oxygen and that's going to come up later, so let's just draw them now, we are going to have two sets of lone pairs because oxygen like six valence electrons, okay? So, where do you think we're going to start? Well, take a look at this allylic positive charge. Remember, allylic just means that it's adjacent to a double bond. Now, we're going to have some possible resonance structures because we have some alternating single and double bonds, so we can first show is that we're going to take this bond and move it over here and what that's going to do is if we copy this next structure in and just keep this that's the same, we're going to get a new bond right here and what that does is it moves our positive charge right here, so we're resonating right now, right? We're moving our charge we're moving our electrons. So, from here notice that again we're left in a situation similar to what we started with, we have a positive charge now adjacent to a double bond, so what do you think is going to happen? Well, this pi bond here is going to take its electrons and make a double bond over here. So, again we're going to get another resonance structure that's possible and for now I'm just going to draw it in this direction, so remember that we still have electrons up here, right? These two lone pairs and now let's see we have a new PI bond out here and here, PI bond here, okay? But we need a positive charge now to be over here on this carbon and again we're going to do the same thing, move our PI bond. So, as a result we're going to get a structure, let's move it now towards the center we're going to get a structure that looks like this, where, let's draw in our pi bond, you guys know where they're going to go? these aren't going to change but our new PI bonds right here. Now fill in the rest of this molecule we have positive charge, lone pair. Now, this lone pair on this oxygen is going to actually come into play now because our last resonance structure is going to be where one of the lone pairs on our oxygen is going to make a pi bond, right? And what do you think we're going to get of our last resonance structure right here, okay? what do you guys think? Well, we're going to have a new PI bond to our oxygen, right? This new bond right here an then alternating bonds all throughout our molecule and you may be thinking where's our positive charge no. Well remember, we can still draw in this lone pair. Now, originally that oxygen had six valence electrons, right? Two sigma bonds and two lone pairs. Now, it has a PI bond, Sigma bond and two lone pairs or a lone pair, so it has five valence electrons, so it's missing a valence electron. Now, so that means we're going to get rid of the oxygen, our positive charge, and if you're able to follow along, which hopefully you were, you'd see that we get a total of five different resonance structures, where we are moving our electrons, you see that our charge actually delocalizes around our molecule. Alright guys, so hopefully that made sense.