Trehalose is a naturally occurring disaccharide used in cosmet...

Question

Trehalose is a naturally occurring disaccharide used in cosmetics because of its ability to retain moisture. The formal name of trehalose is glucose α, α(1→1) glucose. Draw the structure of trehalose. Is it a reducing or nonreducing sugar?

Accepted Answer

Alright, hello everyone. So this question says a geno bios is a disaccharide produced as an undesirable by-product in the starch hydrolysis process in glucose er production, it has a bitter taste and is made up of two glucose units connected by beta 116 linkages. Excuse me, draw the structure of gentle bios and determine whether it is a reducing or non reducing sugar. So here on the screen towards the left side, I have this fissure projection of glucose, specifically D glucose drawn here on the screen. So for the first part of the question, let's go ahead and start by drawing out the disaccharide and then addressing how to tell between reducing and non reducing sugars. So the first thing that needs to happen is given this fissure projection that we have here, we're going to convert this into a ring structure to make our disaccharide, right? So the first thing to recognize if you recall is that glucose is going to form a six membered ring. So that's the first thing I'm going to draw here. Now, when I say six member ring, I'm referring to five carbons from the original molecule itself as well as an oxygen atom. So by convention, right, the oxygen atom of the ring is drawn typically on this top right corner and carbon number one is depicted on the far right side. So just for three dimensionality, I'm also going to go ahead and shade in a little bit this first half of the ring. All right. So now that we have the basic structure, right, the question is how to go about orienting the hydroxy groups on each particular carbon. So before we go ahead and do that, we have one more carbon in the structure of glucose to account for. And that's carbon number six, right? So because we're drawing d glucose, specifically, carbon number six should be pointing above the ring. So that's where I'm going to draw it. OK. So now we can talk about the hydroxy groups. Now, when it comes to converting a fission projection into a ring structure like we're doing right now, the rules are as follows, right hydroxy groups to the right side of the fissure projection point downwards in the ring structure and hydroxy groups pointing to the left in the fissure projection point upwards in the ring structure. So for carbon number two, for example, its hydroxy group is pointing to the right in the fissure projection. So it points downwards in the ring structure. For carbon number three, it's pointing upwards or excuse me pointing to the left in the fisher projection, which means it points upwards in the ring structure. For carbon number four, it's pointing to the right. So it points downwards in the ring structure. Now, the hydroxy group on carbon number five is actually the the oxygen inside of the ring. So from here, let's talk about that first carbon. Now, in the fisher projection, carbon number one is actually an aldehyde which means it's planar, it's sp two hybridized when it becomes a ring structure. Carbon number one actually ends up with a hydroxy group. And because carbon number one is now sp three hybridized in the ring structure, we differentiate between alpha and beta. So in situations like this one where the configuration of the hydroxy group on carbon one isn't specified just yet. We're going to use this curved line or the squiggle line. So to speak to connect carbon number one to the hydroxy group without specifying what configuration that hydroxy group is in. We'll discuss the difference between alpha and beta configuration in just a moment. All right. So here we went ahead and drew our first glucose unit. So now because the dy sack ride in question is made of two units of glucose. What I'm going to do is just copy paste, the first drawing I made. So there is our second unit. So before we go ahead and connect these two glucose units together, let me go ahead and move them towards the bottom of the screen actually just to open up some more space All right. So now it's time for the Glyco cytic pot and the glyco cytic bond is specifically described as a beta 16 linkage. So what that means is that carbon number one of the first glucose unit is going to be connected to carbon number six of the second. So what I'm going to do now is I'm going to start orienting these glucose units a little bit closer to each other. But the fact that the beta configuration is specified matters now because the the glyco cytic linkage is specifically in the beta configuration. The glyco cytic bond should be on the same side as carbon number six. In other words, it should be pointing above the rate. So on the first glucose unit, I'm going to go ahead and edit the bond now so that the oxygen attached to carbon number one is pointing above the ring. And so from there, I'm going to go ahead and bring my second glucose unit closer to that particular oxygen. Now, keep in mind that in order to create the glyco cytic bond in the first place, water is ultimately released as a by-product. So what that means is that the hydrogen of the hydroxy group and the hydroxy group of the second glucose units, carbon number six are going to be removed, right? Because they're going to combine to create water. And so instead, I'm going to go ahead and create a bond between that oxygen attached to carbon one of the first glucose unit and carbon number six of the second unit. Now keep in mind that Carp number one of the second glucose unit doesn't have a specified configuration, which means that we don't know if it's going to be in the alpha configuration or beta configuration. So because of that, we're going to keep it ambiguous and keep this zigzag bond between itself and its hydroxy group. But in any case, this brings us now to the final part of the question is this particular sugar geno bios, a reducing sugar or a non reducing sugar. So when it comes to determining whether or not a sugar is reducing or non reducing, there's one question you need to ask yourself, does the sugar in question have a free anomic carbon? In other words, does it have a free anomic carbon? Meaning it's not involved in a glyco cytic pot? Now keep in mind that the anomic carbon is the one that determines whether or not this particular sugar is in the alpha or beta configuration. So going back to the structure that we drew, the second glucose unit does have a free anomic carbon, specifically carbon number one. So because the answer to our previous question is yes, then it is a reducing sugar. So underneath her drawing here, I'm going to go ahead and add that it is a reducing sugar and there you have it. And so with that being said, thank you. So very much for watching. And I hope you found this helpful.

Trehalose is a naturally occurring disaccharide used in cosmetics because of its ability to retain moisture. The formal name of trehalose is glucose α, α(1→1) glucose. Draw the structure of trehalose. Is it a reducing or nonreducing sugar?

Key Concepts

Trehalose Structure

Reducing vs. Nonreducing Sugars

Moisture Retention in Cosmetics

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