EAS Nitration requires nitric acid to react with a catalytic acid to generate a strongnitroniumion electrophile.
Play a video:
Was this helpful?
Now let's take a deeper look into the mechanism of E a s nutrition. So, as mentioned earlier, nutrition always has to proceed through the creation of a strong nitro Nia my on Electra file. So a nitro Nia my on electrical looks like this. It's gonna be an end with a double 10 at the top. So one over the bottom and a positive charge. Why do you think that's gonna be a strong electric file, guys, it has a full positive charge. That's one of the strongest electricals possible. Okay, that's the perfect type of molecule that benzene wants to react with. Okay, Now, remember that we said there's two different common ways to generate this nitro knee. Um, you could use concentrated nitric acid by itself, by the way, heat never hurt. He's gonna help this reaction regardless of what you re agents you're using. Or you could also just use nitric acid and sulfuric acid together. So I included both of these in our mechanism. Just that you guys can see how they're really the same exact thing. So in this mechanism we have one equivalent of acid reacting with another, regardless of which acid it is. They really do the same thing. One is gonna be a proton donor and one is gonna be the base. Okay, with the sulfuric acid in the nitric acid that makes sense. Sulfuric acid is a much stronger acid, then nitric acid. So it makes sense that sulfuric acid is gonna be the proton donor. Now for nitric acid. We would just imagine that at equilibrium, some of this nitric acid is gonna be donating protons to the other. Okay, so let's go ahead and see exactly which part of the nitric acid would be basic. And it's gonna be this oxygen here with the lone pairs. The reason being that you're going to see later on, it's gonna become a great leaving group. So we would have that if you're proceeding through sulfuric acid that this oxygen would grab one of the hydrogen zahn sulfuric acid. But you could also do the same thing. Guys for nitric acid up here. Okay, it's gonna have the same net result. What we're going to get is we're gonna wind up getting here's our benzene ring. I'm just bringing it down. And now we're gonna get nitric acid that looks like this. It's protein needed. It's now gonna have to. Now it's gonna have two hydrogen on that oxygen and that has just created a water leaving group. Okay, so in order to generate the nitro Nia, my on all I have to do is eliminate with the O negative. So what I can do is I can do an elimination reaction, bring down make a new pie bond and kick out the water leaving group. Okay, with this is now going to give me is a nitro. Nia, my on plus water. Cool. Now I can go ahead and I could do the rest of my mechanism. So at this point, benzene had to bring it down a few times. Now I'm drawing too much. Benzene is gonna attack my nitro. Nia my on What is that gonna look like? It's going to do this, by the way. Positive? Yeah, it's going to attack the nitro or the end, the end. And then it's going to kick out one of these pi bonds and make them into a lone pair because you have to break a bond. This is gonna lead us towards Sigma complex. Right? So let's draw our Sigma complex. I know it's a little annoying, but you guys should get practice with it. So now this is no too right. And we've got double bond here. Double bond here, Positive charge. And now we've just got to draw the whole complex, so I'm gonna move it over. I'm going to move it to this location. And now this is my last resident structure. All right, so we're done with the Sigma complex. There we go. That's our full resident structure. Now, what are you gonna use as the conjugate toe? Eliminate this hydrogen. Remember, we have to do basically, what's a beta elimination on this hydrogen beta to the carbon Catalan? And even though you totally could use the conjugate of sulfuric acids, you could use the negatively charged Os Ohh! Four. I think I said that, right. Whatever. I could write it down correctly, but actually, we're not gonna use that, because typically, most textbooks and most professors are actually going to use the water that left in the nitro group. Okay? And it really doesn't matter. Guys, you could use the water. If you want, you can use the conjugate base of the acid that you use. I don't really care. But just typically it's the water that's used in this reactions. It doesn't matter, because in the end of the day, this would make a Chenault three. I'm sorry, h 03 plus, which is just basically acquis acid, so it doesn't matter. So I'm gonna go ahead, come down and eliminate my each and put the dope on there, and we get our final product. And what our final product is gonna be is it's gonna be our nitric acid. I'm sorry. It's gonna be our nitro group nitrobenzene. Okay, Plus, we're going to get H 30 plus and you know, then you would get, I guess the conjugate of your sulfuric acid. If you had used that, which is O S O four each. Negative. I'm sorry, Oso three h, Okay. Awesome guys. So that's the it for the nutrition mechanism. So let's move on to the next reaction
Reduction of Nitro Groups
Play a video:
Was this helpful?
guys. It's worth noting that nitro groups or nitrobenzene is often used as a precursor to get to Anna Lena. Okay, so remember that Angeline is an amino group on a benzene ring that's called an Anna lean molecule. Okay, and nitro groups can be easily reduced to aniline. So as you can see, a reduction reaction would remove Oxygen's and add hydrogen and make an Elaine. Now, even though we're going to discuss this more in your means chapter, I do want to go through it right now and just kind of clue you guys into some of the most important reducing agents that can make this conversion happen now, the one we always want to start with and probably wanna be our default whenever we think reduction is lithium aluminum hydride. And that's just because this is the most common reducing agent of Oliver organic chemistry. So and it's also one of the strongest, so lithium aluminum hydride will absolutely get the job done and, well, absolutely turn a natural group into Angeline. But there are a few other types off re agents that can do the same thing that you also might see. So just recognize H two and a palladium catalyst. This also goes for a nickel or a platinum catalyst. These would be the regents used in catalytic hydrogenation. Okay, so I'm just gonna put here. These are the regents for catalytic hydrogenation, and that will definitely reduce your nitro group to an aniline now one that's actually really special. Kind of important here is tin to chlorine water or what's also known as Stannis chloride. Okay, that's benzene is just going to get written on because I don't have that much room. Okay, Stannis chloride. Now, this one is particularly special here because we're going to talk a little bit more about this later. This is actually your Onley chemo selective reducing agent. What does that mean? What it means is that by meat by saying that it's chemo selective. What I'm saying is that it has a tendency toe Onley reduce natural groups and nothing else. It actually it's, like, kind of talented at doing that, and it really doesn't like to reduce many other types of groups, So that's gonna be important when we have other groups that are vulnerable to reduction. Stannis chloride is a great choice because it really just hones in on the nitro groups and turns them into aniline. Okay, finally really calm. Introducing agents are either iron or zinc in the presence of HCL. You'll see this all the time. These re agents turn, you know, turn into strong reducing agents that will reduce a nitro group into an alien. So, you know, really, the exact reducing agent that you're gonna wind up using the most is gonna probably be up to professor more than anything else. But keep in mind, bear in mind that all these regions could be used in some way or another to reduce a nitro group to an aniline. My personal favorite is gonna be the tin to chloride, the Stannis chloride. And that's the one that I'm gonna use the most often in this course because I know that it's chemo selective specifically for the nitro groups. So it has very high yields of aniline when we use it. Okay, so let's move on to the next topic
A ntiro group can be reduced to aniline with many reducing agents, as we see below: