You may remember that periodicacidhas the ability to cleavevicinal diols. Sugars contain mutliple diols that can potentially be cleaved, but other functional groups can be cleaved as well. Below we will explore each of them in detail.
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Hey, everyone, in this video, we're going to talk about how you can use periodic acid to cleave or break apart a mono sack ride completely. Let's take a look. So, guys, in general, periodic acid has this ability to cleave visceral Dial's. And this is not a reaction that's unique to sugars. It's actually a reaction that occurs any time that you exposed periodic acid, which I'll show you in a second to a visceral denial. It's always going to split the dial in half, leaving oxygen's on both sides. Okay, now what do we know about sugar's sugars? Have multiple dial's or multiple alcohol's. Andi When I say Dial's here specifically saying Visceral dial's so that the sugars have multiple alcohol's that are next to each other, that could potentially be cleaved. Okay, so what we're gonna learn here is not a new reaction. Completely, what it really is is it's an application of another reaction that already exists. That other reaction says that if you take a dialogue and you expose it to periodic toe acid, it's going to cleave. So now why don't we do that with sugars? And it turns out that the mechanism we're gonna use is even identical to the general oxidative cleavage of Dial's with periodic acid. This is just reinforcing what I'm saying. How this is not a brand new reaction. It's just a application of another reaction. Two sugars cool. So, guys, let's start off with the basics. Visceral dial. Remember that a visceral dialogue is an alcohol, or it's a dialogue that it's that the two alcohols are next to each other. They're not Gemina. Gemina will be on the same carbon, visceral there next to each other. Okay, so you need a visible dial to make this work, we need to expose to some form of periodic acid. Now, here I've gone ahead and drawn out the periodic acid for you. This is what it should look like if you're given this form of periodic acid, which is the most common form. But guys, it turns out that lots of different professors in textbooks for some reason, like toe overcomplicate periodic acid and they like to draw a bunch of different ways. So here what I did is I listed out all the different ways that I've seen it written and that I want you to think of as synonyms for periodic acid. So please don't like I said, Don't overcomplicate it. Just think of them all us forms of periodic acid so you could see Let's just go in order. You could see periodic acid in water, same thing you could see instead of four. Oxygen's three oxygen's that's called biotic acid. But that also functions very similarly. You could see it as I go for negative, which is the anti science that's called period date. And then, finally, you could even see it with six Oxygen's, which is actually just another form of periodic acid. So again, don't worry too much about it. Just think if you see ah lot of oxygen's around and iodine, this is a form of periodic acid, and this is going to be some form of cleavage if Dial's air present. Okay, so let's say that you expose the periodic acid to the dial's what you're gonna wind up getting is this cyclic structure Okay, now you don't need to know the mechanism for this part, but we are going to quickly go over the mechanism for the cyclic part because this part of the mechanism is shared with the General reaction of periodic acid cleaving dial's. Okay, so first of all, let me just name this for you. This structure here is called a cyclic Periodic. Okay, Esther. Okay. The cyclic, periodic Esther is one of the intermediate steps of oxidative cleavage with periodic acid. Okay. And at this point, we formed our cyclic Esther. And now all we need to do is break apart the Sigma bond that's holding the two carbons together. The Sigma bond I'm talking about is this one. This is the one that we're going to try to break apart, cause that's what cleavage means. We're gonna break carbons apart. So the mechanism for this is pretty straightforward. All it is is that you take the electrons that used to be connecting those carbons together, and you make a carbon Neil out of them. So you make a carbon, you lot of one of them. Now, if you could go either way, I could go to the left or to the right. It's gonna be a cyclic mechanism. And it's all concerted. Meaning it all happens at the same time. Now, if I make that double bond Oh, I'm gonna have to break a bond right. So the way that that bond is going to break is that we're going to then take electrons and put them on the I. Okay, so because that oxygen needs to break upon in order to not be positively charged. So we're going to take those electrons away, put them on the I. And now what we have to do is we have to basically keep the formal charge of the I the same. So we're gonna have to break upon on the I and we're going to take these electrons and make a carbon. You'll down here. So, as you can see, we're just redistributing the same electrons that were already there and what we're going to get it. The end is now to carbon deals with this bond breaking right, that bond is gone, and now we're gonna get to carbon eels. So let's draw what that would look like. So what this would look like is on the left side, I would have oh, double bond, whatever that group was on the left. I'm just gonna keep it as a stick because I don't know what that is. And then on the right side, I'm gonna have an H. Now this h Is this a tray here? Okay. And I mean, just to be super clear, this stick is the stick right here. Cool. And then on the other side, I would just get the same exact thing. Just flipped around. What I would get is then I have that stick there and this age here. Okay, that's that. And Oops. Okay, Almost perfect. There we go. So look what we've accomplished, and then you get your biotic acid as a byproduct. Okay? So notice what we're accomplishing were cleaving because we're taking two carbons and we're separating them, and we're also oxidizing. That's why this is called oxidative cleavage. Because I start off with alcohols and I'm ending up here with alga heights. Okay, So, guys, that's the general mechanism. Your professor may or may not want you to know that part of the reaction, but now, in the next video, what I'm gonna do is I'm going to show you what you absolutely need to know the four cleavage patterns for oxidative cleavage. Okay, so let's go. That video
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So this is the part that could get a little bit tricky if you don't have everything mapped out already. So it turns out that different types of alcohols and carbon eels on sugars respond differently to periodic acid. It's not like a one size fits all that. It's always an alga hide. It's actually not. You have to kind of do a little bit of memorization here. So what I've done is I'm tryingto organize it for you the easiest way possible so that you're gonna just be ableto look at this chart and know exactly what to do. Just to repeat, you can't just guess what the product will be. The product is very specific, depending on what type of alcohol or carbon and you're starting with. So what I'd like to start with is, um, basically the difference between an AL dose and a key toast. Okay, so remember that most I mean, sugars always come in either the form all dose or Quito's. Okay, remember that an AL dose at the top is gonna have an alga hide. Remember that a key toast at the top is gonna have a key tone. And that's what I've just drawn here. Okay, Well, that oxygen that either in the Aldo's or the key toast will react with periodic acid. Now, this isn't the same exact reaction as the visceral dial's reaction. Because this is not an alcohol, it's a carbon deal, but it still is going toe oxidize that carbon. You. Okay, so how would we oxidize thes carbon eels? Well, if you're starting off with an alga hide, what you're gonna wind up getting at the end is you're gonna wind up getting I'm going to say this a lot. Formic acid. Okay, now, formic acid is the common name for this molecule. You could also call it methanol ic acid, which would be the AIPAC name. But most commonly it's called formic acid. And that's just the simplest carb oxalic acid possible. It's a carb oxalic acid that only has one carbon. So if you have an alga hide at a terminal end, well, Al guides are always terminal. You're gonna get formic acid as your oxidation product. Now, if you start off with a key tone for a key toast at the top, then you're not gonna get formic acid. You're actually gonna get C 02 So I'm just gonna put your co two. We all know what That's carbon dioxide. So you can see that, um, in both cases were oxidizing. We're adding more bonds toe. Oh, but the exact products are a little bit different. So everyone got that. So far, we've got formic acid. We've got CO two, but we have these. Now we have to look at the alcohol's those air, the carbon eels. But what about the alcohol's? Well, if you haven't alcohol, that is an internal alcohol internal alcohol. What do you mean by internal? There are things on both sides. So it has something on the top and has something on the bottom. What you're gonna wind up getting from that is also formic acid. Yeah, Okay. You're also going to get one equivalent of formic acid for every internal alcohol that you have. Okay, cool. And if you let's say you have a terminal alcohol, Okay? If you have a terminal alcohol now, by the way, this terminal alcohol, I drew it as if it was the bottom. But we know that terminal alcohol's could also exist on the top, because maybe you have a key tone in the tops. Then you have an alcohol there. That's fine. Whenever you have a terminal alcohol, your product is going to be this which is the the condensed formula, for it is C H which is also known as formaldehyde. Oops. Let's try that again. Formaldehyde. And we know that formaldehyde is the simplest alga hide. Okay, so you're either going to get the smallest alga hide or the smallest car books look, acid or co two carbon dioxide. Okay, so that's what you need to know. And if you know these four cleavage patterns, then you should be able to take any molecule, react any sugar. Sorry. Any model sack, right? Reacted with periodic acid and predict exactly what products you're gonna get. Okay, So why don't we go ahead and do a example of this together to get our to get some practice, figuring out what the products would look like
These are the 4 cleavage patterns of monosaccharides you should memorize:
3
example
Predict the products of the following oxidative cleavage
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All right, So here's our first reaction with periodic acid in a sugar. What we see is that we're actually starting off with a key toes here, and we're reacting with periodic acid in water, which is just a form of periodic acid to react with. This is perfect. We know that what we're going to get is oxidative cleavage. Um, and actually, you could predict ahead of time how maney molecules you're going to get. Because how maney carbons do we have total 12345 with oxidative cleavage of mono sack rides. You're never gonna You should be cleaving at every single spot. Okay, If it's a mono sack right, that's in a straight chain, you should be cleaving in every single spot, meaning that every carbon should be its own molecule. Okay, cool. So let's go ahead. And just maybe we can start from top to bottom and you guys can tell me which oxidation product would you expect at each carbon? Let's start off with one. What? Oxidation products. And I'm gonna actually going to use letters and then we'll put it all together. So at carbon A. What would we expect to be the oxidation product. Well, I see it's a terminal alcohol. So I would expect that this is gonna be formaldehyde, and I'm going to draw it on its side so that it looks a little bit more like it did from originally. The O's going this way. I'm gonna draw it this way as well. Maybe it will make it easier to visualize a great job. You guys all said formaldehyde. Good job. Okay, so let's go toe. Go to be So then be Is this carbon? What are we going to get from that key tone? Remember, that key tone reacts with periodic acid to give what? Co two. So let's go ahead and write that in Cedo 10 no, I have one mole of co two. This is getting cool. Let's start off. Let's go down to see. So what would we get with? See what I see with C. Is that is this an internal alcohol or a terminal alcohol? Its internal? Because I have stuff on both sides, Right? So that means that I'm going to get one mole of formic acid. Good job. So I'm gonna go ahead and I'll just draw it like this so that we can keep the O. H and H and the same orientation. Okay. Remember formic acid, you're gonna get your O h and your age and a carbon you'll because it's a carb oxalic acid. Now let's go down to D so d what would I get? Well, guys, this is another internal alcohol because I've got alcohol. I got carbon on the top, Carbon on the bottom. This is not the end of the chain. So this is going to be another form it acid. And then finally, e what am I gonna get for E is guys, this is just another way to draw a terminal alcohol. It's the same exact thing Is that just drawn differently. So should give me the same thing. It should give me a formaldehyde, which we're gonna draw like this, like this. And guys, there you have it. That's actually my product. But let's go ahead and just put it together a little bit more nicely. Um, for the final answer. So the way that we should probably write the final answer is that it's going to be co two plus on to formic acids plus two formal decides and that is our answer. Okay, That wasn't so bad. Right? So now you guys know how to react with periodic acid. This is actually a really tricky example. So any other mon assess like straight chain mono sack, right? Should be relatively easy for you guys to react with. Okay, So, great job. Let's want to the next video.
4
example
Predict the structure of the glycoside products
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guys, this is, Ah, hard problem. Let me go ahead and read it and then try. Toe will try to work through it together in aqueous base, De Glucose has the ability to memorize into small amounts of demand, a pira nose and then on also rearrange into de facto Farinos Fisher glycol. Sedation can then transform these sack rights into, oh, Glick asides. So the two part question says a predict the structure of the black aside products after treatment with acid in methanol. And then be, How could the treatment of those like asides with periodic acid distinguish if EP, memorization or rearrangement is more favorite cool? So that was a mouthful, guys. So this is what it's basically saying in the first little sentence. It's saying that de glucose through two separate processes can either become that thing or this thing. Okay, now I have videos on both of these processes on EP, memorization and rearrangement. So if you're really curious about how to get these exact cyclic sugars, then please go ahead and watch those videos. But because this is beyond the scope of this question, I'm not going to draw out the exact way that we got to these sugars in this question, OK, because we're really trying to focus on is what happens after these form. Okay, Just so just what I'm basically saying is, take my word for it. That D glucose can provide these two cyclic sugars A for a nose and a PIRA knows now where the question really starts, as it says. Okay, predict the structure of the OGE like asides that would form after each of these is treated with methanol and acid. So this part is actually pretty easy because you guys should have learned about rogue like oxidation already. Or also Fisher like oxidation. And you guys should be familiar with which alcohol's react when you react within with which alcohols in a sugar react with alcohol and asset. Do you guys remember Notice that all of the O's are missing their ages so that we're gonna have to predict together if it remains an alcohol or if it gets a metal group on it? So what do you guys think? Here I have potential alcohol's or by potential oxygen's that could now have a methyl group on them. Ch three are all of them going to get sage three are none of them. What number do you guys remember? Well, if you go back to your old like oxidation video, we talked about how Onley one of these can react. And that's because of the intermediate, the intermediate. That's very important. Can Onley form on the an American carbon? So that means that my first product for both of these should have h is remaining in all the places that are not an americ. And then the an America oxygen should get a ch three. And this is what we call an oak like aside and you can see that it's named correctly. It says that now it's d man Oh, piranha side, Which means that you have now an O R group on the an American position. Okay, now I'll get out of the way. Uh, here, just so you guys can see what I'm gonna do here. We can see that it's the same thing. Um, I would just put h is everywhere. That's not an americ. And this is my animated position here. I'm now gonna put a ch oops a c h three here. Cool. So not terrible. Let's scroll up. And we actually already got points for the first part of the question. You know, if this if this was your professors question, at least we're halfway there right now. The next question says, What if you reacted both of these with periodic acid, Right? So let's go ahead and write that down periodic acid for both of these, Could you use periodic acid to prove which one is more favored? Okay, And what we're hinting at here is that periodic acid is probably going to give different products for each of these. It's probably going to give something for the first one, something for the second one. So if we can find out what that difference is, then we could prove is a more common making the pirate the making the pirate pira nose ring, or is be more common making the foreign nose ring. Get what I'm saying. One of these is a six member drain, and one of these is a five member drink, and what we're trying to figure out is which one is more popular? Is it better to go to the six member or better to go to the five member. So what we're gonna do with periodic acid, we're gonna look at the products for each and then those products are going to tell us which one is the most favorite. Cool. So let's look at the cyclic sugar. So the first one, the piranha side, How many places could be Cleve on this sugar? Okay. Now, by the way, some of the rules that we talked about with straight chain mono sack rides don't apply to cyclic, um, like asides. And the reason is because remember that when you had a straight chain, every single position, Haddon Oh, that could react. Okay, but thes aarggh like aside these air cyclic like aside. So that means some of these oxygen's won't be able to react with periodic acid. So we're not going to get the same exact we're not going to get. If you have six carbons, you're not gonna get six products necessarily because some of the O's can't react. We have to look specifically on Lee for which oxygen's are which alcohols are Dial's visceral dial's to each other. And what I see is that this is a dialogue, all right, that there are visceral dial's there next to each other. So that means that I could break here. Does that make sense? That's a visceral denial. I see another visceral Doyal here between these two. So that means I could also break here, and that's actually it. None of these other ones air Dial's because notice on, I'll just use a red X this oxygen. This alcohol here doesn't have any alcohol. Divisional to it. This is not even an alcohol, so it doesn't count. And this is not even an alcohol. So this doesn't count. Does that make sense? So I can Onley Cleve in two places. So that means that if we were just to look at this through geometry, imagine you have something a rubber band, right? Zehava rubber band. And you're going to cut it in two places. How many pieces they're gonna get? Total. It sounds like a trick question, but it's actually I'm just This is just like a physical products here. Like if you take a rubber band and you cut it in two places, you're gonna get to pieces, right? You're gonna get a big piece on a small piece. That's what we're gonna expect over there. So we're gonna expect to products. Let's look at our for and ring are for a nose ring. So how many of these alcohol's count as visceral Dial's? Well, this is definitely one right Those air next to each other so I could cut their What else would count as a visceral denial? Well, um, this'll I mean, so this is not doesn't have any oxygen's around it. This does not count. This, um, does not count because it doesn't have any oxygen's around it. This is not an alcohol, so looks like we're kind of stuck like we don't have that many different places that we could that we could cut. We could only cut in one place. So I imagine you took that rubber band, and you cut it just in one place. How many pieces would you expect to get one? But it would now be a chain. It would now be a string instead of a loop. Right. So we're expecting Is that for the first one? I'm gonna get to pieces for the second one. I'm going to get just one piece now. What would those pieces look like? Well, let's go ahead and draw out what it would look like. So for the first one, do we have any fragments that we actually can match to our four cleavage patterns that we talked about? Remember the four cleavage patterns that you're separating certain things? Do any of these fragments match one of those cleavage patterns? Yep. The one that I'm looking at here is Let me use a different color. This guy right here. Do you see how that's actually an internal alcohol? Because it's an alcohol that has stuff on both sides, and it's getting cut on both sides. So that means that this fragment right here is going to give me formic acid. Okay, How did I know that it was formic acid? Because, guys, that's just a cleavage pattern that we remember that cleavage that when you have an internal alcohol, you get formic acid. Does that make sense? So far, we're gonna get formic acid plus the rest of the chain. Okay, Now for this question, whatever the rest of that chain looks like, it doesn't really help me. It's not applicable, so don't worry about it. Just say that we're going to get that little piece of formic acid plus the rest of the chain. All the other carbons does that make sense? Cool. Now let's look at this one for the five. For the five. How maney do we see any cleavage patterns that are the same or that match up to what we memorized in our page before? No, actually, because no, none of these alcohols are getting chopped on both sides like you would normally expect. Also, none of them are terminal that they can get chopped on both sides. So what that means is, guys that this is actually just going to form one big change, one chain. Okay, that's it. It's not gonna form anything else. So how could you use periodic acid to determine which one is being produced? Well, if, after periodic acid you end up getting formic acid as a byproduct, then you know that you have piranha side. So piranha side after periodic acid after cleavage will give one mole of formic acid. Okay. Whereas if you were to apply the same periodic acid to a five member ring like this, you're just going to get one chain plus no formic acid. Okay, Now, what do we know about formic acid? guys, it's acidic. So you could actually you could probably test out the acidity of the solution to figure out which one is being is being formed. Is it the first one, or is it the second one? Okay, now it turns out, guys, that it didn't ask you to determine which one is more popular or which one is more favored. It just said, How could you use periodic acid to determine which one is more favored or to determine which one is forming? We could look for formic acid. If you're finding formic acid, that means that you're getting the six member drink, and now just you guys know it Turns out that the formic asked. The six member ID ring is much more favored than the five member ID ring. So if we were to actually do this in real life, we would find that periodic acid. When you, when applied to D glucose and efforts allowed toe memories or rearrange, you would actually get formic acid, you get the presence of formic acid because it formed that six member drink. Cool, So tricky question guys. But it was a cool application of oxidative cleavage. Let's go ahead and move to the next video