Show the steps involved in the following reaction:

Question

Chemical reaction diagram illustrating the Diels-Alder reaction with reactants, products, and heat symbol.

Accepted Answer

OK. Hi, everyone. So for this question, let's go ahead and illustrate the steps of the given reaction. Now, what you'll notice about the starting materials given, right, are two compounds on the left side of the arrow is that one of them is what's known as a conjugated dying, right? Because we have two double bonds inside this molecule with one single bond in between them, hence making them conjugated. Now, on the other hand, what we have in addition to the conjugated dain is an all time and if we go ahead and re examine the final product, what's happening here is that the two compounds are connecting together to create a six member ring. And I can tell, right, because we can go ahead and see the substituents on the all kind inside of this ring, which means that they must have been combined together. But in addition to the fact that these two compounds must have been combined together, we also have co carbon monoxide as a by-product. And that sticks out to me when we consider the rest of the ring structure in the conjugated dying itself, right? Because notice how we have one oxygen in the ring as well as one sp two hybridized, excuse me, sp three hybridized carbon inside of the ring separate from the dying itself. So let's keep that in mind. So here, right, if we have a conjugated dyne in their first compound here, then the al kine must be known as a Diop because recall that this is going to be an example of a deals alder reaction. So here, right, our first step of the reaction is going to be a deals all the reaction to go ahead and combine our dying and dienno file together. So the deals all their reaction is also referred to as a four plus two cyclo addition. And the reason for that is because the final six member ring product is the combination of four carbons from the dying, combining with two from the Dyal five. And because the conjugated dying is a ring actually in the beginning of the reaction, the sp three hybridized carbon and the oxygen inside of the ring are going to appear as a bridge, right? They're going to be essentially hovering upwards above the ring structure. So here if I go ahead and I redraw my dying on the bottom here, but I want to make sure of is that the bridge is essentially hovering above the dying itself, right? And I can't forget my substituents though I feel like I could draw this better. So let me go ahead and do that. So here's the oxygen and here's the carbon inside of the ring with my method substituents. So now, right by having this carbon and this oxygen inside of the ring above the dying itself kind of folded over then that makes room for the actual deals or reaction to occur. Right? So now I'm just going to go ahead and draw my diana file so we can see how they combine together. So for the purposes of this demonstration, I will also be numbering the carbons of the diane and the dienno that react. So I'll be labeling the carbons of my conjugated diet one through four and the all kind carbons of the Diop five and six. So this deal deals all their processes going to start by having one of the pythons of the starting all kind essentially move towards the conjugated dying. So in this case, I'm illustrating it or the the pone actually moving toward carbon one of the dying itself. This is the Diop. So as a consequence of this first action, right, the pi bond that's in between carbons one and two right now is going to move over in the space between carbons two and three. And then as a consequence of that, right, in order to make sure that no carbon atom has any more than an octet at any point, right, the pi bond in between carbons three and four is going to go ahead and interact with carbon five from the dial file and that is going to result in the six member ring that's characteristic of a deals alder reaction. So here I'm drawing the six member ring and when it comes to a deal's alder product, there's always going to be a double bond in between carbons two and three due to the mechanism itself. However, because the, the dienno was an all kind and the product is also going to be an all keen. So I've got a double bond in between carbons five and six as well. And from here, always make sure you are adding substituents that are attached to these carbon. So thats what I'm doing right now. These are from the Dino file and I've got my methyl goose from my diet. So now, in addition, right, I can't forget the fact that I'm still going to have one P three hybridized carbon and one oxygen as a bridge above the ring itself. So this right here is only the first step, right? This is that deals all their product or the D A products for short. But this product does not correspond with the one pictured on the screen. So this mechanism cannot just be one step, right? Because the second step must involve the elimination of this carbon and this oxygen that are part of the bridge essentially hovering above that deals all the ring. So the next step in order to facilitate the elimination of carbon monoxide is actually going to be a reverse or retro deals all the reaction otherwise known as a four plus two cyclo elimination. So here in order to illustrate the mechanism, I'm actually going to scroll down, I'm going to scroll down. So to go ahead and start this process off the bond between the P three hybridized carbon and the rest of the deals, all the ring is going to break. So that is going to create a new pi bond in between carbons one and six of the ring itself. Now that is going to displace the Pyon that's already in between carbons five and six of the ring itself. So therefore, the Pyon must move over and it's going to do so and occupy the space in between carbons four and five of the rank. Now by having the pipe on move over like this, the bond between carbon and oxygen or rather the carbon of the ring and the oxygen of the bridge, right? That's going to go ahead and break and that's going to create a new pie bond in between the, the sp three hybridized carbon and the oxygen of the bridge. So the reason why this reaction proceeds forward like this, the reason why it's favored is because we're favoring the formation of a more stable aromatic pot. So that's why this reaction is favorable. And here we end up with a substituted benzene ring, of course, can't forget my substituents. So that's what I'm adding right now. And in addition to this, due to my retro deal's older process, I'm going to end up with carbon monoxide as a by-product and there you have it, here is your final product. So to clarify, right, this process, this entire reaction must take place in two steps because we needed one to undergo the deal's alder reaction to yield the first ring product with a bridge on top. But then in the second step, a retro deals all the reaction was necessary in order to remove carbon monoxide from the ring itself, given that it was a bridge after the first step. So with all that being said, thank you so very much for watching and I hope you found this helpful.

Show the steps involved in the following reaction:

Key Concepts

Reaction Mechanism

Reagents and Conditions

Stereochemistry

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