Hey, fan in this video, I want to do a comprehensive review of one of the most commonly tested topics in carbohydrate chemistry. And that is the topic of reducing sugars. Let's go ahead and get started. So, guys, whereas a lot of different textbooks or maybe even videos online would start at the definition of reducing sugars for this topic, I think it's gonna be easier for you to understand if I first relate the reactions. We're looking at two reactions that we've already learned so that you understand the reactions first, and then I'm gonna go into the definition of reducing sugars a little bit more. Okay, so just kind of hold on tight, it's all gonna make sense at the end. I'm just gonna mix things up a little bit. Alright, that s so what do we already know? What we already learned is that a reaction called bro me in water. It's not called roaming water. Running water is the re agent, and it's called week oxidation, and what it can do is it can provide high yields of Al Danek acid. So remember that we actually had the same exact molecules displayed when we were learning about week oxidation. And what we learned is that if you start off with an AL dose and you react it with bro mean in water, what you're going to get through a mechanism that you don't really need to know is the formation of Anel Danek acid. So you already know this. This reactions called week oxidation wonderful, but this reaction has a limitation. The limitation is that even though it works really well, it does not undergo a visible transformation. Now that actually isn't a big deal in modern days because we have an M R and a lot of different analytical techniques that we can use to verify for reaction has completed or not. But thinking back to the 18 hundreds, when these reactions were first developed, it was kind of nice toe have re agents that would turn red or turn blue or green once they reacted. So the reactions were gonna learn about our reactions that accomplish the same exact transformation while giving us visual cues. And those reactions are gonna be the tallest test. The Benedicts tests and the failings tests and these tests are going to reduce are going to react with what we call reducing sugars, which I'm gonna to find very soon into all demonic acid. But they're not just going to do it the way that roaming water did it. They're going to do it while also providing specific visual indications that the reaction took place. Okay, so the reaction proceeds forward by oxidizing. Oops, I should put oxidize test. The test will oxidize any sugar capable of forming a straight chain Aldo sor Quito's. And this is going to be our definition of reducing sugars for right now. So when I said that it reacts with reducing sugars were going to say the reducing sugar is any sugar that's capable of forming a straight chain AL dose or Quito's so D mantles. Is that a reducing sugar? Yeah, because it's a straight chain. Aldo's right. So what we're saying is that these reactions Tallinn Benedict Spellings, they're all going to do the same thing. They're gonna turn that demand nose into their gonna oxidize it and turn it into a carb oxalic acid. And then they're going to give us specific visual indications. Okay, so let's go really a little bit more into what the re agents are for each of these that you can know what to expect when you look. When you find this on the exam, let's say so. Let's start off with Tallinn, which is the most common of the three. So the Ta Lin's test has been around for a really long time, and it seems like every book or every professor has their own unique cocktail of re agents that they like to use for the Tomlin's test. So sometimes you might see it drawn out like this. Sometimes you might see it drawn out like this. They look very different from each other, but there are commonalities between them, and what the commonalities are is that there's always gonna be some elemental silver. There's always gonna be some ammonia, and there's always gonna be some base. So what I want you guys to think about is I don't want you to memorize the exact order of their letters of the re agents because they're actually like five other ways that that could be drawn. You might see it simply as just like silver oxide and ammonia. NH three Uh, eso I don't really want you to focus too much on the exact letters as much as the general picture that if you're reacting some kind of sugar with silver ammonia, a combination of silver, ammonia and base that's going to be a Talyn's region. Okay, now, what does Hollins do? It does the same thing as bro me in water. But instead of just getting your AlDAN ic acid, you're also going to get a silver mirror on the outside of your test too, so that it looks silver and you're gonna know. Oh, there was a reducing sugar present. Okay, By the way, we're assuming. Like I said, this is a reducing sugar. Now is what we call a reducing sugar. Next, we have Benedicts and fell wings test. Now, Benedicts and fillings test actually do the same exact thing. They react with your reducing sugar, they turn it into a no Danek acid. They just have a different visual indication. And the visual indication they have is that they turn into copper one oxide see you too. Oh, and they form a brick red precipitate that settles to the bottom of the test to Okay, now you might ask Well, what's the difference between Benedicts and fell Ings guys, it doesn't matter. They're just slightly different complexes of copper two plus. But as long as you see some kind of copper two plus, it's going to be Benedict or fillings. Okay, Now something's interesting about this. One is that it actually starts off blue and turns red at the end. So it's a kind of cool transformation that would you would know for sure that reducing sugar was present. Okay, now slight disclaimer, guys, not every professor. Not every textbook, not every homework will require you to know all these three. Some professors just care about Stalin's. Some professors just care about Benedicts, but I just decided to include them all in this lesson because it's like, Why not? They're also easy there. Also similar. It's like the more you know now you know that there are three different tests that I'll do very similar things. You should just know the difference in their visual indication. Okay, so one last thing I want to point out before we move on to kind of the bottom of the page, which is that one of the biggest misconceptions of reducing sugars is that students here, the term reducing sugar, and they think that that means that the sugar is going to get reduced, right? But what are we saying? We're actually not saying that at all we're saying is reducing sugar is a sugar that can be oxidized. It's a sugar that has an all dose present like this one that could be oxidized. So if it's important for you guys to know that, that's a very easy trick that a lot of people mess up on. A lot of people don't understand it, but a reducing sugar is actually a sugar that can eventually be oxidized. Okay, And then, I guess one last disclaimer, which is that if you're paying really close attention, you might notice that key tones usually can't be oxidized. Very well. So you might be thinking, Johnny, why would a key toast react in an oxidation reaction, guys, because usually these reactions are in a base solvent or a base catalyst. So in base, we actually know that key toeses Can Todd memorized all doses so it would wind up happening is that the key toes can react. It just has toe tot, um, rise into the Aldo's first, and then it can. It can react through this reaction. So basically, that's why we say that a reducing sugar is any sugar that's capable of forming an AL does or Iquitos. Because if it's Akihito's, it can always just taught him rise back to the Aldo's and then react. Okay, guys, So we're done with this part now, just toe. Really? Briefly Recap, um, Tallinn Benedicts and felons test do the same thing as weak oxidation, except that they provide visual cues. And now we're going to do in the next video is I'm going to go dive way deeper into the definition of reducing sugars because my definition right now is any sugar capable of forming a straight chain Altos Marquitos. But there are actually a lot of different situations and a lot of tricky situations that you need to be aware of to know if it can form an Al Dosari Quito. So in the next video, I'm going to show you guys the definition of reducing sugars and how to predict if a sugar will be reducing sugar or not. Let's move on to the next video

So what is a reducing sugar? Alright, guys. So I made it sound really complicated in my last video. It's not there. Just specific rules. You need to make sure that you can be aware of the first one is easy. A reducing sugar is any straight chain mono sack ride. So literally it doesn't matter if it is an AL dose or key toast. If you see it in straight chain it for sure is a reducing sugar. Okay, so that takes care of a lot of your examples, But it could also be any cyclic mono sack, right? That's a ring Die sack writer. Sugar derivative that has a least one cyclic hemi a Seattle group present. Okay, so, Khenyeza towel. You guys should know that, But here is a reminder. Ah, cyclic ass. It'll would have our groups on both sides. So you have O r o r. Remember that a cyclic hammy a Seattle would have an o. R on one side, but then a free alcohol on the other and O h on the other side. This is basically present on a lot of different mano sack right sugars. Um, and if you have a Hemi as a tall present. That is a reducing sugar. Okay, now you might be saying, Well, why? What's the big difference? Why does it matter? Because guys, Hemi hospital groups can be hydrolyzed two straight chain sack arise, whereas a settles cannot. Once you're in the a settle, this is actually what we call a glycol site. Remember, like asides, guys or like specifically, like an oak like aside. Remember that you put the carbon on there, and then it's It's pretty much locked in place unless you reacted with a lot of acid and hydrolyzed it off. But a cyclic amines total is constantly hide relies ing back to the straight chain, whereas an oak like aside is not. So. That's why a cyclic amines. It'll will be a reducing sugar because we would expect that in solution, it's going to slowly hydrolyzed back into the straight chain structure. Does that make sense? Whereas the other one, as an oak like aside, it's locked into place unless we specifically want to hide, realize it with acid? Okay, so, guys, let's go ahead and do the next question. As an example,