24. Carbohydrates
Monosaccharides - Ruff Degradation
Opposite to Kiliani-Fischer, aldose aldehydes can be oxidized to carboxylic acids and then decarboxylated to shorten chains. This will utilize a reaction we learned before, except now it is applied to sugars. Let's try and refresh your memory.Â
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Monosaccharides - Ruff Degradation
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Hey, guys, in this video, I want to talk about a reaction. That's kind of opposite to kill Janni Fisher. Chain lengthening. And that is the rough degradation, which is a chain shortening reaction. Let's look into it. So, guys, we know that Kalyani Fisher exists toe length and chains. We would use thes scion oh, hydrants and then reduce them and eventually would get a new album, Hide Group at the top. But it turns out that reactions have also been designed to take carbons away. And one of the ways that we learned how to remove carbons in organic chemistry to is through reaction called Dhi Qar box elation. You guys remember the car box elation? It was a reaction where ah, carb oxalic acid turns into CO two gas and you lose the carbon in the process. Well, uh, genius, uh, in a genius move, they decided to apply that to sugars. And they said, Hey, if we can turn the alga hide from a sugar into a car box, little gas ID, then we could probably d car box related somehow, right? And that would shorten the chain. And that's exactly what we're gonna learn. How to do today. So every time you do one of the rough degradation cycles, you're gonna lose one carbon, and you're gonna lose it because one co two molecule is flying off into the atmosphere. Okay, Now, unlike Kill Eonni Fisher, where Remember how Colleoni Fisher would make two different ep Immers because you were adding a new Kyrill center and you didn't know which direction the O. H would go, but in a ring, I'm sorry. In a change shortening reaction, we're actually having less carol centers. So that means that we're gonna have a stereo specific product. We're not gonna have to worry about a mixture of EP immersed like we do with Colleoni. Fisher. Okay, Now, um, just as just as a quick disclaimer, the C two stereo center is the one that's lost in every cycle. So what we're talking about is this guy right here. Notice that right now I picked De Manos as my original model sack ride, which means that the O. H. Has faced this way. But afterwards that information is gonna be lost because it's gonna turn into an alga high notice that right now it's Cairo. But after my reaction is gonna be a Cairo, so there's gonna be no mawr stereo specific information at that position. Okay, cool. So I know you guys were ready to get into the re agents. I've been talking a lot. So what are the re agents used for? A rough degradation. Well, guys, the first one you already know it's bro mean water. So remember that I said scientists were thinking, Hey, there's gotta be a way that we can do a D card box. Elation, guys. The easiest way that we know to turn a Aldo hide into a carb oxalic acid into Anel Danek acid is just use week oxidation with growing water. We've done this before. You don't need to know the mechanism, but you do need to know that this will oxidized to a carb oxalic acid. Cool. That's the easy part. We already know that from before Now. The part that's a little bit more tricky is that this is actually not the type of carb oxalic acid that is easy to DIY car Boxley. Do you guys remember on this? You can go ahead and look this up If you type in Dhi Qar box elation into the search bar clutch. You'll see my whole video in this reaction, but from memory do you guys happen to remember which types of part of carbon slick ass is Where the easy ones to D car Boxley. It was the beta carbon Neil or the Bay Taquito Uh, carb oxalic acid. So remember that it would always help that if this is your Alfa Carbon, you wanna have, like, a carbon kneel next to it and that would make the whole mechanism go quickly and you'll be able to easily dehar box later. Okay, But we don't have that. In fact, we have no other carbon meals. So technically, this shouldn't really Dhi Qar box like that easy. And that's why we're gonna need very special re agents to do the next step. The next step is actually not going to proceed through the same D card D card box elation mechanism you learned in the past. It's gonna proceed through a new mechanism that's actually mostly unknown. All we really know is that it's a radical mechanism because it uses hydrogen peroxide, which is a radical initiator, and then an iron sulfate complex. These two things together what they're going to do is not only are they going to use radicals to dick our box late, but they're also going to oxidize. Okay, so they're going to do all that. They're going to use radicals to D card box. They take it off and then tow oxidize the final alcohol that's left. So what you need to know here is not really the mechanism, but what happens and how it works. So remember that in D card box elation, you cleave off whatever car looks like acid you have, and the sea and two O's becomes CO two. So that's where this is going to go. It's gonna become CO two gas. Okay, now, these three sugar, I mean, sorry, not three sugars. These three hydroxyl groups are the same as the three hydroxyl groups over there. The only difference is that now, my C two position right here, like I told you guys, is gonna become an alga hide. So it's gonna basically turned into a double bond. I have it drawn to the left. Over here. Here I have it drawn to the right. It doesn't matter because it's tribunal planner, So there's free rotation around that bond. It doesn't matter what structure you draw it in there. The same thing. Okay. And again, I'm not going to show you the whole mechanism. But you should just know that this is what this step does. The radical D card box elation step takes off the alga hide and oxidizes that see to alcohol into an alga hide. Okay. And then notice, guys, What we're left over with is on Lee the last three hydroxy holes in the same place, everything else above. Those last three hydroxy was got chopped off or changed. Okay? And that is how we get the Arab a nose, in this case, which is, um, the degradation products of de manos cool. Awesome guys. So hopefully that means sense. Let's go ahead and move on to a practice problem.
Here are some practice problems to test what we just learned. Good luck!
2
example
Which aldohexoses produce the same Ruff Degradation product
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circle the Aldo Heck sauces that would produce the same rough degradation product. If none would share a degradation product, then just right N a. So, guys, before we can determine which ones are going to share a product, we need to do the same transformation. All of them. So, do you guys remember how to do this? It's pretty easy. All we're gonna do is take off the top carbon meal. So let's just take that off and pretend it doesn't exist anymore, okay? If it even if it makes it easier for you, scratch them out because they really don't matter anymore. Okay, Now, this is gonna be a little bit makeshift, but try to turn, try to draw it in such a way so that you can turn that top. Oh, now the one that used to be at sea to turn it into an alga hide. So I'm just gonna do this Double bond, double bond, double bond, double bond. Those h is there going to go away in the mechanism so we can even just scratch them out. Cool. All right, so now we've really done. The transformation is just in a very like crude way, but we've actually done it in a way that's very understandable and easy to follow. Now remember, guys, the Carbonneau facing towards the left is the same exact thing as the Carbonneau facing towards the right for glucose. So don't worry about the direction of the carbon deal. All we really care about is for any of these four sugars. Do they have their alcohol's facing exactly the same directions so they can be the same? Aldo Pantos. Do you guys see any that are exactly the same? So I do see one that looks kind of similar, which is D glucose over here, related toe l Gulas, which is over here. Okay. And if you I don't know if if you weren't paying attention, maybe someone could pick these because they would think Oh, but if you flip it, then it's the same thing. That's wrong. Don't think that way. These air different. Aldo Pento says guys, because this is not ah, symmetrical molecule. We have the same group on both sides. Remember, the top is gonna be an alga high. The bottom is an alcohol, so you can't just flip it over to make that thing thes air distinct alcohol, distinct sugars because they have their alcohols in different positions. Then we look at this one. This one is definitely different. And we look at this one, Guys, they're all different. So none of these share the same degradation products because of the ones that I picked. These four do not share degradation product. These are all unique degradation products. So I'm gonna go ahead and write and a cool Does that make sense? Awesome. So let's go ahead and move on to the next video.
3
example
Predict the product for the following reaction
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predict the products for the following reaction. If multiple steps air indicated then state all the intermediate structures. Cool. So, guys, let's figure out what we're working with first and then actually draw it all out. So what I'm starting off with is in Aldo Heche sauce called D. It does. And my first reaction appears to be bro me in water. So I know this should be a week oxidation. Yeah. My second one is peroxide and an iron three complex or island and water. Now, actually, guys, I drew it this way because I want you guys to know that, um, you could see that iron sulfate complex written in a lot of different ways as long as you have some kind of elemental iron. Three. Plus, that's all you're really looking for. You're just looking for something that's iron three plus to promote and toe do this radical reaction. Okay, So, guys, you should know that this is gonna be the radical de car box elation. And I could even say dick our box elation oxidation. Right, Because we know that the alcohol gets off, the alcohol gets oxidized to an alga hide at the end. So let's draw the intermediate structures because it says if multiple steps are indicated, draw all of them. So the intermediate structure is gonna be the car walks like acid of the first one, which is gonna be this Ohh! Cool. So this would be intermediate structure one, because all I did was, like, oxidized that top alga hide to a carb oxalic acid cool. And then my second and last step is gonna be to get rid of it. So then what I'm gonna do is I'm gonna just draw this part with an alga height sticking off of the top. So it's gonna be I'm really just drawing the bottom part first, So Ohh Ohh! What? What I'm drawing What's in that circle? Ohh! C h 20 h h h h cool. And now we know that this position gets oxidized toe on Alba hide. So let's draw that double up on oh, each plus C +02 gas. That is just gonna be right there. Cool. And that's my breath Degradation. Guys were done. That was it. Awesome. So we're done with this practice problem. Let's move onto the next video
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