Oxymercuration - Video Tutorials & Practice Problems
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This is the second of three ways to add alcohol to a double bond. It is similar to acid-catalyzed hydration in terms of products, but the mechanism is WAY different.
1
concept
General properties of oxymercuration-reduction.
Video duration:
5m
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Video transcript
All right, guys, we just talked about how you can use acquis acid toe. Add alcohol's two double bonds, threw acid catalyzed hydration. But it turns out that there's actually more than one way to add alcohol sexual bonds, and that's actually a huge focus of this section. So I'm gonna do now is I'm gonna show you guys an alternate reaction that we could use that also adds alcohol's two double bonds, and it's called Oxy Mercure ation dimmer curation. So, first of all we're gonna notice is that this is just a really long name for a reaction. So I personally like to shorten it, and I always call it instead of that long name. I usually just call it Oxy Mark. And that's fine. If you just say oxi Merck. That just means it's oxy, Mercury ation, dimmer curation or reduction to Fine. Okay, so in general, what do we see? Like, what's the general regions that we use for this we're gonna find is that you have a double bond, Of course, And then we're gonna react it with this weird re agent. That's a mercury with two acetate or Seattle groups on it. Okay, so that's with O A. C means it means a Seattle groups. And I'll show you what that looks like in a second. So you have that any of water. So this is really the first step, and this is called the Oxy Mercure ation step. Now, if you're confused like how you remember this, well, eventually you are gonna need to memorize this. But one way that I like to maybe make it simpler is that notice that the word Oxy Mercure ation has mercury in it Mercury and notice that the re agent of Oxy Mercure ation is h g, which is mercury. So whenever you just see the h g, you automatically know this is an oxy mercury ation. In fact, we won't see any other reactions with mercury until order to. So you're pretty safe that if it's a mercury, that's oxy mark. Okay, then the second step of this is to react with any BH four and some kind of base like any Ohh. This is called the reduction step or the dimmer curation step. Okay, now, typically, that's the way things work when you have something above the arrow on something on below it that could either mean that you have a region and it solve it or that you just have a two step reaction. Sometimes you're gonna see these written a separate steps, like one and two. But sometimes you just see it written without the numbers. And you're just supposed to know that what's on top of the arrow is the Oxy mark part. What's at the bottom is the reduction part. Okay, Regardless, we're gonna learn thes re agents. Don't worry. But regardless, look what happens. We still get and alcohol. So let's go ahead and look at the general features of this mechanism. So basically, the intermediate for Oxy Merck is not going to be the same as hydration instead of being carbo cat. And what it's gonna be is what we call a bridged. Well, I okay, and that's gonna be a big deal. When it comes to predicting products, that's actually gonna matter a lot. Okay, the stereo chemistry here is actually gonna matter. It's gonna be decided decisively. Anti. Okay. So what that means is that anti stereo chemistry is the same way of saying that at the end you're gonna get trans products. Okay, so if you ever hear me say anti? That just means that at the end you're gonna expect your alcohol and your H two b trans to each other. Okay? And like I just told you guys, the products are alcohol's. Okay, so now let's come to the last two fax. Would we expect there to be rearrangements in this mechanism? Remember that rearrangements happened when we have carbo Catalans? Do we have a carbo Karan? No. So it turns out that this reaction is actually not gonna have any rearrangements because it doesn't have any car. Boquerones. I'm just gonna write that right here. No, Carbo Karan, in case there's actually no way for it to rearrange it all. Finally, is it gonna follow Mark Avnet. Cauvery geochemistry? Yes, it is more common, cause rules still gonna apply. Even though it's not a cargo carrying, it's still gonna apply. All right, so now when we look down at her general product, it actually makes sense. But it looks like notice that what I have Oops. Just a second notice that I have is that once again, this is my Markov Nankov location, and I attached my alcohol to it. Okay, so my alcohol is gonna go. Markov Makov. On top of that notice that the H that I added on the other side is going towards the dash and the O. H. Is going on the wedge. What that means is that I have a Markov Nick Aww, anti alcohol. Does that make sense? Because basically, it's markovic off because it wants the most stable location. It's anti because my h and the O. H that I added our trans to each other. And it's an alcohol, all right, So even if you didn't know the full mechanism, you could still predict the products just based on these fax. But obviously we need to know the mechanism, so let's go ahead and get started with that.
Opening of 3-membered intermediates/molecules always results in anti-addition.
General Reaction:
2
concept
Acid-catalyzed oxymercuration-reduction mechanism
Video duration:
9m
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Video transcript
So for this mechanism, the first step, just like the first step of all these mechanisms, really is Elektra Filic Edition. I'm gonna take my dope on, and I'm gonna try to find something. That's Elektra Filic. So in this case, that's actually gonna be the Mercury, because when I drew out H g o a c two the O A. C two are these things right there? There's two of those acetyl groups. Okay, so those groups air pulling electrons away from the mercury, giving that a very, very strong, partial positive. So what this means is that I'm actually gonna get a new interesting Siris of arrows. I'm gonna get that this double bond attacks the H G because it's positive and that in order to make that bond a break a bond. So I'm gonna break off one of these ASIO groups and it's gonna leave, Okay, but on top of that, there's one more area that's gonna form, which is that the H G. Instead of just attaching toe one side or the other like I would usually do for an H, the H G is actually gonna go ahead and grab back. So we're gonna get to Arrow's gonna get one arrow going to the G. I'm gonna get another arrow from the H g back to the dole bond. What this is going to do is it's gonna give me Ah, bridge I on that looks like this like step two in step to what we see is that now the h g from here is attached right there toe both of the atoms. It's attached partially to the top one and the bottom one. This is unlike hydration. Because, remember, hydration. I would always attached the h just toe one, and then we'll get a car, will cada And on the other. In this case, I don't get a car, will cut and get abridged. Ion. All right, Now, notice that the always see here just has to do with the fact that one of the oasis is still attached. Okay, I'm also gonna get plus o a c negative. That just left. All right? Just you guys know. All right, so now I've got this ion in general is called a bridged ion. Specifically, it's called a mercury. Um, I on It's mean, It's an ion made out of mercury. Okay? And What you're gonna notice is that there's a positive charge distributed throughout these three atoms throughout this one. This one and that. Okay, why is there a positive charge? Because actually, since these air partial bonds, they're not a full bond. What that means is that thes carbons don't have enough total bonds. Alright? Basically, both of them is kind of like making a half bonds. So it adds up Thio. Ah, full positive deficit. There's basically one bond missing. All right, so my question is now, how do I get rid of this intermediate? Because it sucks. It's really unstable. Okay? And it turns out that the nuclear following this case is gonna be water. Why is their nuclear fall water? Because if you look up towards my re agents, water is the second part that's given to me for Oxy Mercure ation. Now that nuclear fall could change, but in oxy markets always gonna be water. Okay, so now we go down here and we see that water has electrons, right? It has plenty of electrons to give. And I got this positive charge so inside of the ring. So this water is really attracted to that positive charge. Now, the question is, which side of the ring is it gonna attack? Is it gonna attack the top part, or is it gonna attack the bottom part? Because both of these air different. It could either attack the top part and become tertiary or the bottom part and becomes secondary. Okay? And it turns out the way we judge, which cited attacks, is by the side. That's gonna have the most positive character. Okay, well, let's think about it. I just told you that there's basically partial positives on all of these atoms. Partial, positive, partial, positive, partial, positive. It's being distributed throughout, but it turns out that one of these atoms is gonna have the most positive charge. Why? Because it's going to be the one that's the most stable with a positive charge. So between the two carbon atoms, which one do you think is gonna be the one that's more stable? The one that's a secondary carbon or the one that is a tertiary carbon? Which one's gonna like to have a positive charge? More tertiary. So that means that this one's actually going to be more positive, and this is actually just gonna be a little bit less positive. Okay, so you can imagine there's a little bit more positive density at the top. And what that means is that the water since its negative since it has electrons, it's going to go for the one that's the most positive, which is the top one. So you're going to go for the most substituted. Okay, this mechanism. Just so you know, if you've already learned it, it's an S and two mechanism. It's actually a backside attack. Okay, so if you don't know that, that's fine. Alright. But anyway, what's gonna happen here is that the water attacks there. I'm gonna just gonna raise some of the stuff that we're not using. Okay, So the water text, the top part. And now I've got too many bonds to that carbon because that carbon is now gonna have four bonds. 12 three, four. That's the new bond that's being created. And it has that partial bonds of the mercury. So if I make up on, I have to break up on and I'm gonna break the bond to the mercury. Okay? Now, this brings us to an interesting pattern that we're going to see all throughout this section, which is that any time that you have a three member ring or bridge or anything like that and you break it open, that ring is highly, highly strained. Okay, Bond angles do not want to be at 60 degrees like that. So when you break open part of the ring and it snaps open, the groups are gonna end up facing opposite directions. And the reason is you can think of it almost like a loaded spring. When once you break it open, both groups are gonna go opposite directions because they want to get as far away from each other as possible. Okay, so what that means is that if my water, let's say, attacks from the front from the top, let's say that the water attacks from the top of this of this 300 ring, and they break open the part with the mercury. That means the mercury is now going to go down because the mercury is going to try to snap open to the opposite side of where the water attacked. Okay, What this gives us now is the reduction step. So now what I have is I have a water that attacks from the top. Remember that? I said that. Let's say attack from the top if it attacked from the top. That means that the method group that used to be here ch three got pushed down to the bottom case. And now it's at the bottom. Well, another thing that happened was that the mercury was part of three member ring and it broke open. So that means if the waters on the top the mercury has to be at the bottom. And that's what we have right here. The mercury is now going to face towards the bottom side. Okay, so that's the end of our oxy mercury ation step. Now we have to get to the dimmer curation or the reduction step. Now, the fun part about this is that you actually don't need to know the mechanism. So I'm just gonna right here. Don't need MEC. Okay? Why is that? Because it's really complicated, and it has to do with stuff they haven't learned yet. Okay, In fact, reduction in general, you don't have a good grasp on yet. Okay. Oxygen reduction is like its own topic in organic chemistry. And you haven't really gotten their full yet, so we're not going to really bother with that too much. All you need to know is that basically have a base that's going to wind up taking Lee a proton from my water to become alcohol. And then you have a reducing agent. By the way, any beach four get used to it now is a reducing agent. We'll talk about this more later in the semester, okay? And that's going to reduce. Basically, a reducing agent adds hydrogen is two things. Okay, so that's going to reduce my mercury into an H. So at the end, what I'm gonna wind up getting is a product that looks like this. Like I said, you don't need to Another mechanism. You just need to be able to predict that it's gonna look like this. I would get now on alcohol at the top. I would get my method group towards the back because I got pushed there. Okay. And then finally, I would get the h towards the back. Okay. So noticed that my mercury now became an H. And now notice that once again, this is now showing you how I'm getting my Markov. Nick aww. Or just I'm gonna call the mark. Anti alcohol. Okay, Because my my alcohol went to the more substituted location. Which was the water. The water text, the more substituted Markov. Nick. Aww. Then it's anti because the bridge snapped open so it had to face opposite directions. And then it's an alcohol because we used water as the nuclear file. Does that make sense? Cool, guys. So this is a very important reaction for you guys to know. It's basically taught in pretty much every textbook. It might show up on later standardized test stuff like that. And obviously you needed for your exam. So make sure that you know everything about it literally. All right, let's go ahead and do some practice with Oxy more.