Ozonolysis Full Mechanism - Video Tutorials & Practice Problems
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Now we're going to discuss the exact mechanism for ozonolysis. This mechanism is a little on the crazy side, but we'll teach you how to get through it!
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General Mechanism:
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7m
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What's up? Everybody in this section, we're going to take a look at the full mechanism for the oxidative cleavage. Reaction owes analysis. The mechanism for the analysis reaction proceeds through intermediates called ozone IEDs. Alright. And what those needs are are there. There are cyclic molecules that were formed by the addition of ozone. Okay, so I was gonna have three oxygen's, and they're always gonna be really unstable. Alright. That instability in these intermediates is what drives our reaction forward. Okay? And those analysis is always combined with a reductive or a oxidative work up. All right. The reductive work up forms Alba hides and key tongues while the oxidative work up forms carb, oxalic acids and ketones. Okay, RV agents for the reductive work up are typically either D m s, which is a dime ethel sulfide that we see right here. Or zinc and acetic acid, right? For our oxidative work up, we typically use H 202 which is just hydrogen peroxide. Okay, Now, with those analysis, the mechanism proceeds the same through the first three steps, regardless of which work up we're gonna use. Okay, so we're gonna break this up and first look at that. The first three steps that are common to either oxidative or reductive analysis. And then we'll look at the reductive work up mechanism and then the oxidative work up mechanism after that. Okay, so the general mechanism is three steps, and each step has three hours. Okay, so all those analysis mechanism has three steps and three arrows per step. Okay, In our first step, we react our team with our ozone molecule. Alright. What is our ozone molecule missing here? Yeah, it's missing its charges. Okay. Remember, we have a positive charge on this middle oxygen and a negative charge on that oxygen there. Okay, that negative charges gonna act Is a nuclear elements gonna add to our double bond? Okay, so this negative charge is gonna come in and add to our alky in there. Aren't we made upon? So we have to break a bond. So we break the pie bond in that Al Qaim. An attack are oxygen at the far end of the ozone molecule. Okay, that breaks the oxygen oxygen pi bon and puts a lone pair on oxygen. Okay, so we had our three arrows. They're they're all moving in the same direction that gets us to our first chosen. I'd intermediate alright in this intermediate is called Malos and I'd all right, remember are those night? Intermediates are unstable. Alright, not instability is gonna drive this next step. Alright, But first you may be wondering where is this hydrogen right here. Where did that end up? Well, remember, this first step is gonna be a sin edition. All right? Where are ozone ads? Either from the top of that all keen or the bottom and the stereo chemistry of that Al Qaeda has retained. So what I mean by that is that hydrogen is cysts to the Ethel right there. Okay, so it's gonna be assist to the ethel in our malos. And I'd intermediate here so that hydrogen is gonna end up onto this wedge right there. All right, so from here this second, step it again. Has three arrows all right? We want to start at one of the oxygen's. That's making a bond to carbon. Alright, so either the one on the right or the left, and it doesn't matter here. All right, so we could just choose one. We'll choose the one on the right here and will make a carbon oxygen double bond. All right, that's our first arrow. We made a bond. We have to break a bond, and we're gonna break the carbon carbon bond that connects the two oxygen's. All right, so that is this bond right here in green. We're gonna break that bond, and we're gonna make another carbon oxygen double bond. All right, again, we made a bond, so we have to break another bond. So we're gonna break this oxygen oxygen bond and give that top oxygen a lone pair. Okay, so that gives us two molecules again. We haven't Alba hide on the left. All right. And then we have that other intermediate on the right. What are we missing on? That molecule you're missing are charges again? Okay, so we need a negative charge on that oxygen in a positive charge on this oxygen. Okay? And what we do next isn't actually a mechanistic step. It just makes it easier to draw the next mechanistic step. Okay, What we want to do is scoop up this molecule with the charges and flip it back towards ourselves, okay? And when we do that, we end up putting that negative charge on the bottom here and the positive charge right next to it. Okay, The reason we do that is because these two molecules need to react together. All right? And if you remember, uh, the DI polls on carbon eels always look like this where we have a die, Paul pulling electrons away from the Carbonell carbon towards that oxygen. Okay, so both of these Carbonell carbons have partial positive charges. So they're Electra Filic. All right, then we have an oxygen with a negative charge. That's gonna be nuclear filic. Okay, so we're gonna do a nuclear Filic edition here, and this step again has, or this mechanistic step again has three arrows and this negative charge will draw an arrow to the carbon carbon There. We made a bond. We have to break the bonds. We're gonna break a carbon oxygen pie bond and that is going to attack the other Carbonell carbon. All right. Our third in last arrow for this step is breaking the other carbon oxygen pie bond in giving that oxygen alone Pair. Okay, so that is our last step there. Alright. And again, uh, we have three mechanistic steps with three arrows per step. All right. And we eventually end up getting here to this molecule. This is our last owes Night Intermediate. And this one is actually just called ozone. I'd all right. And if we wanted to track our carbons throughout this mechanism, All right. We could say that those carbons, their stay on the right side throughout, All right? And they end up right there. The carbons on the other side and this hydrogen stay on the left side throughout, all right? And they end up opposite the yellow ones. Okay, so that is our general owes analysis mechanism. In the next video, we'll go ahead and take a look at the mechanism for the reductive work up.
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concept
Reductive Workup Mechanism:
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3m
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All right, Now, we're gonna take a look at the mechanism for the reductive work up. Okay, So we're gonna start where we left off from the general owes analysis mechanism where we formed owes inside, All right? And we're gonna add in our one of our reductive work up re agents, which is this dimethyl sulfide or d m s. Okay, what happens here is R D. M s attacks are ozone. I'd intermediate, so we'll draw this again down there. Alright. R D M s attacks one of the oxygen's that's already making a bond to another oxygen. Okay, so one of either this oxygen or that oxygen, it doesn't matter which, but it has to be one of them. All right, so Italy make a bond to one of those oxygen's. We made a bond, so we have to break upon. All right, we're gonna break the oxygen oxygen signal bond here, and that is going to swing over and make a carbon oxygen pie bond. Okay, we made a bond. So again, we have to break a bond. So we're gonna break the carbon oxygen bond there, and we're gonna make a carbon oxygen pi bon on the other side. Right again. We made a bond, so we need to break a bond, and we're gonna break the carbon oxygen bond there on the other side and give those electrons back to our soul for their okay. So overall, we're doing four arrows in this step and we're making to carbon meals. Okay, So if we were to track the electrons from this oxygen oxygen double bond, where do they end up in our products? Yeah, well, they end up making the pie bond from our AL died. Right. We have a metal in a hydrogen there. Okay, We have a metal in a hydrogen here, so that bond is gonna be the pie bond over here. Okay, What about the electrons in this green bond here? Where do those enough? Yeah, well, those end up being the pie bond on our other carbon. Um, okay, we have the metal and the ethel on either side. All right, We have our ethel in arm Ethel on either side in the pie bond. Here came from that carbon oxygen double bond. Okay, if we were to look at the other carbon oxygen bond that broke, we know that That bond, what's highlighted? And pink. That bomb there ends up being the oxygen sulfur pie bond in our product there. Okay, So our product here is D M S O. That's what the D M s turns into. All right. And since it was the reductive work up, we form an alga hide and a key tone. All right. And with our reductive work up we conform. Alba hides, we conform, Ketones. We can't form carb oxalic acids. Okay, In the next video, we will take a look at the oxidative work up mechanism.
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Oxidative Workup Mechanism:
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1m
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What's up, guys? We're finally getting to the oxidative workout mechanism, right? And sorry to let you down, but there's not actually a mechanism here. Okay, this is unknown. Alright? I know you're all super bummed about that. You don't get a learn another mechanism, but it is important to know what an oxidative work up does in a nose analysis reaction. Okay, When we react, are those night intermediate with our oxidative work up re agents here H 202 which is hydrogen peroxide. Anything that would have turned into an alga hide in our reductive work up will turn into a car box. Cilic acid. Okay, so here we form a car box Cilic acid and a keto. Okay, so if we look up to our reductive work up of the same owes nine intermediate, we formed a key toe and Alba had all right, we basically just oxidized that Alba hide up to a car box. Cilic Acid. Okay, so in euros a night, intermediate anywhere that you see a hydrogen attached to one of these carbons making to oxygen Sigma bonds that hydrogen will become an Ohh in your car box Cilic Acid. Okay, so super important to know super useful reaction teas. Okay, go ahead and try the practice problem below, and then in our next video will come and solve it.
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example
Predict the products and show the mechanism:
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12m
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All right, guys, this question is asking us to predict the products and show the full mechanism for this reaction. Alright, the first thing we need to do is just identify what reaction is occurring. All right? And to do that, we need to identify what are re agents are. Okay, so we start off and we have an AL Keen. Alright. In our first step, we're reacting that with 03 All right, this is a huge clue. Anytime we see 03 which is ozone. We should automatically be thinking of our owes analysis reaction. Okay. And in our second step, where reacting with GMs, remember, D m s is dimethyl sulfide, which just looks like that a sulfur atom with two ch three is attached. Okay, so we're reacting. And al Keen with ozone followed by D. M s. What would you call this reaction if you had a classified really specifically? Yeah. This is gonna be owes analysis with a reductive work up. Okay. With a reductive work up. Okay, So whenever we're doing those analysis reactions and were asked to predict products and show mechanisms, the easiest thing to do first is just to predict the products. All right. Remember, Johnny taught you to use the scissors to just cut this bond and separate it. We can still do that here, even though we have to show the mechanism. All right, so we want to think about using our scissors to cut our Archym right down the middle. Okay, so we're gonna cut this out keen right down the middle. We're gonna pull those two pieces apart. Okay? So on the left, we're gonna have that five member dream. Yeah, All right. It still has half of that double bond. What do we put on the other half of that double bond? Yeah, we put our oxygen there. Okay. The other side, the other half will just have that one or two carbons there and then half of that pi bon. What goes on the other half of the pie bond? Yeah, the other oxygen. Okay, I'm gonna fill in the hydrogen there, but remember, any time we see a hydrogen coming off are all keen with a reductive work up. It'll be a hydrogen oven. Alba, hide in our product. Okay, so those are two products. Now, let's just show how we make them with our mechanism. Okay. What is the first step of our mechanism? Yeah, we just need to react. Are all keen with ozone. Okay, so ozone 03 remember, is three oxygen is bound together. We have oxygen. Let's draw this in blue. Actually, we have an oxygen and oxygen and oxygen. Okay, We need one oxygen, oxygen, double bond. It doesn't matter which side we do it on. I'm just gonna put it on the left. That oxygen gets a positive charge, okay? And the other oxygen gets a negative charge. Okay, so there's our ozone molecule that will add to our Al Qaim. Okay, this negative charge will come in, make a bond to a carbon of our Al Qaim. And remember, we could have drawn our ozone the other way, where the negative charges on the other oxygen. Okay, then we just would have attacked that left Carbon of our al Qaim. It doesn't make a difference in the mechanism or in our final product. Okay, but we'll make that bond there are made of bonds we have to break up on. So I'll break this carbon carbon double bond and make up onto oxygen again. We made a bond, so we have to break a bond. So we're gonna break this oxygen. Oxygen Pi bon Right there. Okay, there are three arrows for this step in the mechanism, right? We're ready to draw the product of that step. So here we'll have our five member ring. Okay? It has that metal in this hydrogen. And then we have our two new bonds to oxygen's just like that. Okay. You may be wondering why didn't I show stereo chemistry here? And really, the stereo chemistry of the intermediates doesn't matter because we end up making these carbon eels. Alright, that are sp two hybridized. Okay, So SP to hybridize atoms don't have any stereo chemistry that we don't have to worry about. Our wedges are dashes, so we don't really care about it in the mechanism unless we're asked to show the stereo chemistry of our intermediates. Okay, so this is our first. I was not intermediate, remember? It's called Malos, and I'd all right. And to get to our next intermediate, we again need to react with three arrows. And again, they're all going to react in a cyclic way. Our first arrow starts at one of the oxygen's making a oxygen carbon bond. So we'll choose this one on the right. But again, it doesn't matter which one, and we'll make that carbon oxygen pi bon. Okay, we made a bonds. We have to break upon Which bond are we gonna break? Yeah, we're gonna break the bond that connects the two oxygen's. Okay, so this green bond right here, we're gonna break. And we're gonna use those electrons to make another carbon oxygen pie bond. Alright, again, we made a bond, so we have to break another bond. So we're gonna break this oxygen oxygen bond right there. Okay, So if we want to draw the product from all of these atoms on the right, what would that look like? Yeah, I would look pretty similar to an alga hide. Okay, so we'll have the metal and the hydrogen there. Alright, We'll have an oxygen carbon double bond attached. Alright. And then we'll have an oxygen attached to that oxygen. So Okay. What? Will our charges be here? Yeah, We'll have a negative charge on this oxygen and a positive charge on this oxygen. What will the other half look like this half highlighted in blue. Yeah, that will just be a key tone. Okay, so we'll have that. And then a key tone just like that. Okay. What is our next step? Well, remember, first we have to flip this molecule over. Okay? So I'm just gonna go ahead and redraw them. We can flip over either molecule, but I think it's easiest to flip over the one with the charges. Okay, So remember, we want to scoop it up and flip it towards ourselves. Okay, So what that will look like is we'll have all of this flipped over. We'll have our oxygen are other oxygen will solve our charges. A negative charge, a positive charge. All right, well, keep the other side exactly the same. Just that five member during with the carbon in with a key tone. Okay. What happens here? Yeah, Well, again. Just like every step here. We have three arrows, all right? And they all move in the same direction. Okay, So what we want to do is use that negative charge to attack our carbon carbon of art. Keto alright? And do a nuclear Filic edition we made upon. So we have to break upon these electrons will come all the way over to the other. Carbonell Carbon of the molecule that originally attacked. Okay, we made a bond. So we have to break upon is our last arrow. So we break this carbon oxygen pi bon right there. Okay, so we're at three arrows there were done with this step, and we formed our next ozen. I'd intermediate. Yes, which has an oxygen right here. Okay. A carbon attached to that, That is are five member ID ring. Okay, on the other side, we have our hydrogen and are metal, okay. And then attached to those we have our two oxygen's. Okay, I know that could be kind of hard to follow, so I'm gonna map everything out here, all right? This these two oxygen's right there that are attached to each other are gonna be the two oxygen's that are attached to each other in this owes. And I'd intermediate. Okay, This carbon attached to those two oxygen's is gonna be that carbon there on the left. All right. And then this carbon in that oxygen are gonna be the other carbon and oxygen of our ring in this intermediate. Okay, so this is our next to me. What was this one called? Yeah, this one is called Just owes inside, All right? And this is where our owes analysis stops and our work up begins. Okay, so now we have to do our reductive work up with D. M s. All right, so we need to draw on our D. M s, which is just a sulfur with two methods. What is the first arrow that we need to draw here? Yeah, I remember. We have four total. The first one goes from the sulfur to one of the oxygen's making an oxygen oxygen bond. Alright, It doesn't matter which one. We'll just go ahead and go to this one on the left. Alright, so we just made a sulfur oxygen bond. Once we make that bond, we have to break a bond. We're always gonna break the oxygen oxygen bond. Okay, that oxygen, oxygen bond, we'll swing over and make a carbon oxygen double bond. And actually, I drew that bond to the wrong place. This oxygen goes right, is bonded to the same carbon as the other oxygen. All right, but it doesn't change the mechanism except here, so that oxygen oxygen bond goes to form a carbon oxygen bond right there. Okay, we made a bond, so we need to break upon. So we're gonna break the other carbon oxygen bond of that carbon and use those electrons to make another carbon oxygen pie bond. Okay, We made a bonds. We have to break another bond and draw our fourth arrow of our reduction step. And we're gonna break this carbon oxygen bond right there. Give those electrons back to sulfur. Okay, so we have our four arrows of our reductive step, and that gets us to our final product. Okay, so our alga hide. Let's get rid of this highlighting here to show that our Alba hide here in yellow comes from this oxygen. That method on that hydrogen while our key tone in blue comes from this oxygen and all of those carbons of that five member. Great. Okay. What is our one byproduct that we didn't show? Yeah, it's a D m S O. Okay, so we also have d m s O, which is just dime Ethel. Self oxide. Okay, so that is our analysis mechanism there. Let's go ahead and move on to the next section.