Benzene undergoes electrophilic aromatic substitution reaction...

Question

Benzene undergoes electrophilic aromatic substitution reactions with aziridines in the presence of a Lewis acid such as AlCl₃.

a. What are the major and minor products of the following reaction?

b. Would you expect epoxides to undergo similar reactions?

Accepted Answer

Welcome back everyone to another video. Number one. What are the products of the electro pilic aromatic substitution reaction of benzene and the given epoxy in the presence of a loic acid such as aluminum chloride? Number two, do you think that Aines will react? Similarly, we're going to start with the first part of this problem in which benzene reacts with an oxy rain derivative in the presence of aluminum chloride. And what we want to do is just think about the mechanism of the reaction and we're going to use a short mechanism. So we have our benzene ring and essentially we have to recall that oxygen has two long pairs of electrons. So it forms that coordinate bond with aluminum and it gets activated specifically. What we're going to do is just draw that oxygen which is now bonded to aluminum. And therefore, that means aluminum gets a negative charge. Oxygen gets a positive charge. And we also have that methyl group. Now we will have a nucleic attack by the pi bond of benzene. Let's choose one of our pi bonds and let's attack the more substituted carbon because it has more partial positive charge due to the fact that if you open the ring, you will form a more stable secondary carbo cion as opposed to a primary one on the other end. So we have our tech, we're opening the ring and we get our first intermediate. So we're going to draw benzene. Once again, we're going to add our pi bonds. And now what we noticed is that we are forming our carbon carbon bond. So first of all, we are going to draw that bond and we will calculate how many carbon atoms we will have within our side chain. So we are now going to draw carbon number one and carbon number two. So first of all, we have one, then the second one, that second one is still bonded to oxygen and oxygen is bonded to aluminum chloride. And what else do we have? Well, essentially we're forming our carbon carbon bond at the position that still has that metal group. And of course, our final step is, is usually to restore aromatic because we have the positive charge. So we want to eliminate the hydrogen atom from that position. And for that purpose, we are just going to transfer our electrons between oxygen and aluminum towards the formation of the oxygen hydrogen bond. And this will allow us to restore aromatic in which we obtain our final product. This will be our major product. We can essentially draw it carefully. So we can draw our six member train once again. Now we are going to add our c side chain with three carbon atoms that would be 12 oxygen now bonds to hydrogen and there is that metal group remaining, that would be our major product. What about the minor one? Well, to get our minor product, we are just going to attack the ant that is less substituted and has less positive charge. And we can essentially get our minor product by performing another attack. So let's draw our epoch side, which is now bonded to aluminum chloride, oxygen has a positive charge. Aluminum has a negative charge. And now the minor product is obtained by the attack at the less substituted position, opening the ring and we can actually separate that part. So we can clearly see that we are drawing another reaction. Now let's draw the result and intermediate and now let's introduce our bond. So we are forming our carbon carbon bond. We are going to get 123 carbon atoms within our side chain. So that would be 123, right? So let's add 1 to 3. And specifically what we noticed is that carbon number two will have oxygen. So if that's carbon, number one, carbon, number two will have oxygen, which is still bounded to aluminum chloride. Aluminum gets a negative charge. And finally, we want to restore aromatic just as we did before. So we are going to transfer our electrons and restore our Matic by adding a pie bond. So now we get our minor product. We are going to draw that Bens and Wang and now we are simply adding our alcohol group. So now that we got our products, we can label them as major and minor. Let's go ahead then to that. So our first major product was our alcohol and we got another alcohol as the minor product. OK? Now let's label them. That would be the major one and we got the minor one. Now, regarding aziridine, the second part of the question, yes, we can definitely expect them to react similarly. The reason is very simple. If we essentially replace what we had wet our different the electro, in particular, we're going to change oxygen to nitrogen. We will expect to observe a very similar scenario. And the explanation is very simple if we think, let's say about the major product, nitrogen has a similar similar electron negativity to oxygen. So it is making the electro pilic center significantly electro pilic and susceptible to the nucleic attack. So we're going to attack the electro pilic position and open our ring. So definitely we expect a Xero des to react similarly, we don't need to draw the product. However, you would follow exactly the same steps as we did before. The main reason for you to understand is that Aines would react similarly because nitrogen is significantly electro is significantly electron. It has a high electronegativity which is similar to that of oxygen. And therefore that increases the electrophysi of the three number rank within the position that we are attacking. So let's label our products. We got our major product and our minor product. And for the second part, we can say, yes, Aines will react similarly due to the fact that nitrogen has similar electronegativity to oxygen. Thank you for watching.

Benzene undergoes electrophilic aromatic substitution reactions with aziridines in the presence of a Lewis acid such as AlCl₃.
a. What are the major and minor products of the following reaction?
b. Would you expect epoxides to undergo similar reactions?

Key Concepts

Electrophilic Aromatic Substitution (EAS)

Lewis Acids and Bases

Reactivity of Epoxides

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