Propose a mechanism for the following reaction:

Question

Chemical reaction diagram showing a benzene ring reacting with HCCL3 in the presence of peroxide to form a product with CCl3.

Accepted Answer

All right. Hi, everyone. So for this question, let's go ahead and draw a suitable mechanism for the reaction given below. And here we're reacting to dying with HCCL three in the presence of peroxide to yield the given ring structure with ac cl three substituent. So here, right, recall that this is going to be an example of the cyclic of the dine in question because notice how by the end, right, we're creating 26 member rings now here, right? The fact that we have peroxide in solution is going to indicate that this reaction proceeds through a radical mechanism, right? Because recall that it's very easy for peroxides to form radicals due to the relatively weak bond between our two oxygens in the center here. Now, radical mechanisms always proceed in three steps, right? The first of which is your initiation in which your first radicals are going to fort. Now, in this case, like I said previously, it's very easy for peroxides to split into two distinct radicals. So that's exactly what's going to happen. And in our initiation step, the bond between our two oxygens in the peroxide will break to yield two radicals. Now from there, right? Recall that your next step is going to be propagation. In other words, it's kind of like a domino effect in the sense that our first radicals react with other substances to create new radicals and therefore drive the reaction forward. So in our propagation step in our propagation step, notice how we have to have CCL three attaching to the carbon structure of our ring, right. So here one of our radicals that comes from peroxide is going to combine with our HCCL three and that's going to produce an alcohol plus a CCL three radical. So here's our carbon trichloride radical. And now the carbon trichloride radical is going to participate in propagation, right? Because it's a new radical that's formed and it's going to interact with our organic starting material, our diet. And what you'll notice here is I actually read, drew our dying on the screen here. So I'm just going to move it down a little bit and I'm actually going to move my propagation step as well. There we go. I'm doing this because I want you to see that this is all part of the propagation step. So that's why I try to combine them together. But anyways right now that our carbon trichloride radical has formed, it's going to interact with our diet. Now, specifically, it's going to interact with this highlighted hydrogen or specifically the highlighted carbon hydrogen bond, right? Because it's going to form a brand new radical like so here the two electrons are going to split, right. And now in our intermediate step, there we go. Now in our intermediate step, we're going to have a radical on the actual dien starting material. So here we have a radical word that highlighted hydrogen used to be attached to. And so that that radical due to its proximity to one of the pie bos in our dye is going to contribute to resonance. So here, right, instead of having the secondary radical, a radical is going to participate in resonance with the pie bond to yield a more stable or rather a radical in a different position. So here we're going to see some resonance at play. And here I'm just trying to make sure that this carbon chain looks half decent. But here, like I said previously, right, our pi bond and our radical have since moved and now that radical is going to go ahead and interact with the second pie bond of the dying to close the bridge, right and create 26 member rings by the end. So a radical goes in the center as does one electron from the pi bond and that's going to yield a different radical. And that like I said previously is what's going to close the bridge and create our 26 member rings used together. So here's a python and here is our radical and now recall it previously, right, our carbon trichloride radical interacted with that hydrogen to become HCCL three once again. So now HCCL three is going to come back, right? It's going to come back and it's going to interact with are radical after the 26 member rings have since closed. So our radical here is going to go ahead and take a hydrogen or rather the hydrogen from HCCL three. And that in turn is going to regenerate our carbon trichloride radical. So now we have only one pie bond in our organic intermediate. So now the remaining pi bond is going to interact with our carbon trichloride radical so that it can go ahead and attach itself to a carbon. So here one electron from the pi bo is going to interact with the radical and then the other is going to form a different radical somewhere else. So now we have our carbon trichloride substituent where it is in the final product. But right, to address the fact that we have one more radical, we have to bring in yet another molecule of HCCL three because our last remaining radical is going to take the hydrogen from HCCL three and regenerate our carbon tri fluoride radical. And finally our final product. But right, we have to get rid of all radicals in solution, right, because at this point, we do want the reaction to stop. So this is where we introduce our third and final step, which is termination, right where our radicals are going to combine together and the reaction therefore is going to end, right. So recall first and foremost, if we go all the way back, right to the very beginning, our initiation step created two radicals stemming from our peroxide. But in the propagation step, we only used one. So the other one, the second one has to be accounted for in this case. So that second radical from our peroxide is going to combine with our carbon trichloride radical. They combine together and they at long last right, terminate the reaction because by this point, right, no more radicals are going to be present in solution. So I know it was a lot, right? But this is the entire reaction mechanism, right? And here, right, our reaction mechanism followed three distinct steps. The first was initiation in which our first radicals formed in the beginning. Now, during propagation, right, the radicals that we formed after the initiation step react further with the other starting materials present, they yield new radicals and creep or continue so to speak the reaction shape. So in this case, right, when it came to our organic dye in the beginning, right, eventually the two pie bons in the dyne contributed to the formation of two fused six member rings. And then once we had our carbon trichloride radical attach itself to the organic starting material in our termination step, all remaining radicals combine together so that the radical mechanism would end. So with that being said, I know, this was, this was a lot. Right. But thank you so very much for watching and I hope you found this helpful.

Propose a mechanism for the following reaction:

Key Concepts

Reaction Mechanism

Nucleophiles and Electrophiles

Transition States and Intermediates

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