Draw all possible resonance contributors for the two carbocati...

Question

Draw all possible resonance contributors for the two carbocations in the preceding reaction. Use the resonance contributors to explain why 1-naphthol is the major product of the reaction.

Accepted Answer

All right. Hello everyone. So this question is asking us for the following reaction determined all plausible resonance contributors for the carbo cat on intermediate. And here we have a reaction scheme that we'll discuss later. But for now, the second part of the question is asking using resonance explain why Anthro 10 is the major product. So as mentioned before, right, the reaction scheme in question is shown here at the top of the screen and it actually features an oxide ring opening. Now the oxide ring opening features two distinct carbo cion intermediates that form two distinct products. One of them on the top is anthro 10 which is the major product. And the second one is androzene tool. Now, if I scroll down here a little bit more, I went ahead and redrew the two carbo cion intermediates that were shown to go ahead and draw out the resonance structures. But before we go ahead and draw out the resident structures, there are a few key principles to consider when it comes to drawing residents in the first place. Right, recall that resonance describes the movement of electrons within a given chemical species right now. Curved arrows similar to reaction mechanisms showcase the movement of electrons double headed arrows showcase the movement of a pair of electrons while single headed or fish hook arrows show the movement of one electron. Now, when it comes to drawing out resonance structures, it's important to recognize that the carbon skeleton of your species should not change as a result of resonance. It's only electrons that is pi electrons or lone pairs are the only things that are going to be moving here. And so on that note, when it comes to drawing out resident structures, keep the principle of high to low in mind. So what that means is that electrons will tend to move from areas of high electron density towards areas of low electron density carbo cations, for example, are areas of low electron density. So resonance structures should depict electrons moving towards carbo CS, not away from them. So in addition to everything that we've talked about up to this point, resonance structures have to have a valid Lewis structure. And at the end of it, all the number of electrons, specifically the number of unpaired electrons when dealing with radicals must remain the same. So with this in mind, let's start with the first carbo on intermediate here. So for the first rebel c ion intermediate or actually both of them, we have a rebel cion adjacent to not only a hydroxy group but also a series of alternating double bonds within our ring structure. So as mentioned before, right, electrons move from areas of high electron density to areas of low density. So the double bond closest to the carbo cion should move towards the positive charge because the cion is the area of low electron density. So here right, as mentioned before, the nearest double bond to the carbo cion should migrate towards the carbo C on itself. And from there we get our resonance structures. Now, resonance structures are separated from each other by this double ended arrow here. So let's start with the first creel cion intermediate. All right. So at this point, the double bonds of the first two rings are going to stay where they are. The difference now is that the pi barn that was farthest to the right has since changed positions. And so what that means is that now the positive charge in the resonance structure is going to be on the carbon opposite to the one containing the hydroxy. So the movement of electrons has actually moved the position of the carbo cion. And this is something that I actually should have mentioned before, right, all resonance structures should have the same charge at the end, the charge should not be changing while drawing resonance structures. So that concludes our first resonance structure, our our first cruel cat eye on intermediate. So for the second one, the same principle is going to be true, right, as a result of the movement of the closest double wand towards the carval cion, the positive charge is now on a different position. So now the positive charge is going to be on a carbon that is part of two ring structures, two of the fused rings here. So now that we have the ResMed structures recall that it's the first one that leads to the formation of anthro 10 which is the major product. So why is that? Well, the difference lies in what's happening to the second ring. In other words, the fused ring in the middle. Now when it comes to the first carbo cat on intermediate, both resonance forms maintain the aromatic of the ring in the center. So the first cruel cat I can be delocalized without compromising the aromatic of this middle ring. The same cannot be said for the second carbo cion. The de localization of the second carbo cion intermediate via resonance requires the destruction of the middle ranks aromatic. But when it comes to the second carbo cion intermediate, in particular, it's not just that aromatic city is compromised, rather the formation of the second carbo cat on intermediate and therefore its residents de localization actually means that the middle ring is now anti aromatic and recall that going from aromatic to anti aromatic is never plausible under normal conditions. So really the formation of Anthro 20 specifically the formation of the resonance structure that leads to anthro 20 should not even exist under normal conditions. So this just goes to show why Anthro 10 is the major product. So for the final answer, I would go ahead and highlight this first set of resonant structures explaining the formation of Anthro one all. Now, as for the explanation to summarize, we would say that the Carbo Cion leading to and 1310, I'm realizing now that cut off the rebel Cion leading to Anthro 10 is more stable because it's the localization does not destroy the intact Benzi. All right. So I did briefly pause the recording so I could go ahead and rewrite the final answer. But here it is right here. It's showing the de localization of the first carbo Cion intermediate. And the explanation reads that the Carbo Cion leading to anthro 10 is more stable because its de localization does not destroy the intact benzene. And so if you watch this video all the way through, thank you so very much for doing so. And I hope we found this helpful.

Draw all possible resonance contributors for the two carbocations in the preceding reaction. Use the resonance contributors to explain why 1-naphthol is the major product of the reaction.

Key Concepts

Resonance Structures

Carbocation Stability

Nucleophilic Aromatic Substitution

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