Monosaccharide Configurations

in this video, we're going to begin our discussion on mono sacha ride configurations. And so, of course, in your previous organic chemistry courses, you guys learned how to determine the configurations of Cairo carbons. And so you may already remember from your previous courses that configurations of mono sack, right Carol carbons can be designated using two different systems. The first system is the con angled pre log system, which uses the letter R and the letter s to designate the configuration. And the second system is Fishers Convention, which uses the letter D and the letter L to designate configuration and so moving forward in our course, we're going to talk about each of these two systems and separate video, starting with the con angled pre log system. So I'll see you guys in our next video.

So in this video we're going to refresh your guys memories of how to use the conning gold pre log system to designate absolute configurations to Cairo carbons using the letters R and s. And so the con angled pre log system is really just a synonym for R s configuration. And so if we take a look at our sugar down below, Glessner outta hide, of course, the Kyrill carbon is going to be this carbon atom right here in the middle. Notice that the carbon at the top is not Kyra because it has a double bond or two bonds leading to the same chemical group oven, oxygen atom and the carbon at the bottom is also not Kyrill because it has two bonds leading to the same chemical group of ah hydrogen atom. And so again, the Onley reason that this Cairo carbon in the centers Cairo is because it has four distinct chemical groups attached to it. And so, when we're trying to determine the configuration of this Cairo carbon using the conning gold, pre log system and RS configuration, these are the three steps that we really need to consider. The first is going to be to assign priorities number one through four to each of the chemical groups that are attached to the Cairo carbon. And the way that we assign priorities one through four is based on the atomic numbers of the atoms that air in each chemical group. And so, if we take a look at these four distinct pathways that air connected to this Carol Carbon, we have ah hydroxyl group going this way. We have this entire group going this way. Then we have this group going down this way. And last but not least, we have this group going to the left. And so these highlighted groups are the four chemical groups that we need to assign priorities to. And so, of course, we can see that this oxygen atom is going to have the highest atomic number. So this is going to be our priority number one. And then this blue group over here has a carbon atom, but so does this green group down below. And so after you look at the initial atoms that are attached, you then have to start to look at the substitute wants or the other atoms that air branching off of those carbon atoms. And so notice that the carbon atom at the top has a double bond to an oxygen, whereas the carbon at the bottom on Lee has one single bond to an oxygen, and so the double bond is going to have a higher priority. And so we can give this pathway priority number two. And then, of course, this carbon atom is going to have a higher atomic number than this hydrogen atom. And so this carbon atom down here is gonna get priority number three. And then, of course, that leaves our hydrogen atom up here with priority number four. So now we can get rid of these backgrounds here, and we've assigned our priorities. So now this first step is complete. And so in the second step, all we need to do is determine if the priorities 12 and three ignoring for our in a clockwise are configuration or if they're in a counterclockwise s configuration. And so it's important to associate clockwise with our and counter clockwise with s configuration. And so when we took a look at our priorities down below, we are going to look at 1 to 2 2 to 3 and three back toe, one ignoring four. And so what you can see is that when we go from 1 to 22 to three and 3 to 4, that is a counterclockwise configuration. So this appears to be appears to be an S configuration because of the counter clockwise pattern here. And so now that we've completed step number two, the last and final step is step number three right here. And that is on Lee. If priority number four is on a wedge popping out of the page at us at that point, we need to assign the opposite configuration that it looks like. And so right now our configuration looks like an S configuration. But we have to check priority number four and see if it's on a wedge popping out of the page. So when we look at priority number four, we can see that it's on a horizontal bond of the Fisher projection. And this is where it's super important to remember. The nature of Fisher projections recall that all horizontal bombs and official projection are popping out of the page as wedges. And so that means that our priority number four is indeed on a wedge popping out of the page. And that means that we need to assign the opposite configuration that it looks like. And so even though this looks like a counterclockwise s configuration because priority number four is on a wedge popping out of the page, this is actually going to be and our configuration. And so what we can say is that this Cairo carbon here in the center, it's going to have an R configuration. And so, really, this is the steps that we need Thio take to determine our s configuration. And it's very possible that your professors might expect you guys to remember how to do this. So moving forward, we have some practice problems to help refresh your guys memories. And so, hopefully this was a good refresher for you guys. And in our next video, we'll talk about how to determine d l configuration using Fisher's convention. So I'll see you guys there

So now that we've refreshed our memories on how to designate R s configuration using the con angled pre log system in this video, we're going to talk about how to designate d l configurations using Fisher's convention, which is actually more commonly used on carbohydrates, since Fishers convention was developed, using carbohydrates and so Fishers Convention again is going to designate either D or L configurations relative to glisten her alga hide and anti immerse. And so Glessner outta hide is just the name of one of the smallest and simplest sugars that exist. And again, an anti a MERS are just referring to non super imposible mirror images. And so if we take a look down below at the image here in this box, notice that we're showing you the two glitzier outta hide in anti Immers. And so what's important to know is that the D configuration is going to be assigned to a Cairo carbon when the hydroxyl group of that Cairo carbon is pointing to the right and the L configuration will be assigned to a Cairo carbon. When the hydroxyl group of that Cairo carbon is pointing to the left of the Fisher projection And so you can think l is for left. And so if we take a look down below at our glycerol to hide and anti MERS notice that this an anti, um are over here has its hydroxyl group on its Cairo carbon pointing to the right of the Fisher projection. And of course, if the hydroxyl group is pointing to the right, then we must assign a D configuration. And so that means that this glitzier out I'd in Antium er here is the d glitzier outta hide form and has D configuration. Now notice Looking at this and anti more over here, the mirror image Uh, it's hydroxyl group on its Cairo carbon is pointing to the left of the Fisher projection. And of course, ah hydroxyl group pointing to the left corresponds with l configuration. And so this glitzier out I'd and anti armor over here is indeed the L Glessner outta hide form and has l configuration. Now. One thing that's important toe note here is that Fishers convention will Onley properly work with standard Fisher projections and so Fishers convention on Lee works with standard Fisher projections and recall that way back in our previous lesson videos. We covered standard Fisher projections and so recall that standard Fisher projections will always have the Carbonnel group on the top of the Fisher projection or towards the top of the Fisher projection. And so notice that with these glitzier out of hiding Anne Summers, the Carbonnel Group is hidden within the alga hide group here. And so the Carbonnel Group is indeed on the top and also recall that with standard Fisher projections, the longest carbon chain must be vertical. And so when we take a look at these glitterati had an anthem er, over here notice that the longest carbon chain is indeed vertical in both of these. So these are standard Fisher projections that are being shown, and most of the time you will be given Fisher projections that are already in standard Fisher projection form. So that makes your job a little bit easier now, usually under most circumstances that you'll encounter in your biochemistry course, Deacon figuration are going to equal are configurations, and usually L configurations are going to equal as configurations. But this is not always going to be true under every single circumstance. Again, this is going to be usually true under most circumstances that we will encounter. But if you wanna be ah, 100% safe, then all you really need to do is determine our s configuration separately from D l configuration. All right, so now that we know how to determine D l configurations, let's go ahead and determine the d l configurations for all of the Cairo carbons in these two glucose and anti um er shown over here. And so if we take a look at this first Kyrill carbon right here, notice that it's hydroxyl group is pointing to the right and of course, O H group pointing to the right corresponds with D configuration. And so that means that we can give this Cairo carbon right here a d configuration. So we'll put a little d right next to it. Now moving on to the next Cairo carbon right here, notice that it's hydroxyl group is pointing to the left. And of course, a left pointing hydroxyl group corresponds with l configuration so we can go ahead and give this Cairo carbon right here an L configuration, and then notice that these next to Cairo carbons both have their hydroxyl groups pointing to the right, which again corresponds with D configuration so we can go ahead and assigned both of these Cairo carbons d configuration. So now moving on to the next glucose and anti um, are over here Notice that its first Cairo carbon right here has its hydroxyl group pointing to the left, which of course, corresponds with l configuration so we could go ahead and give this Cairo carbon and l configuration notice that the next Cairo carbon right here has its hydroxyl group pointing to the right. So it's gonna have a D configuration so we can put d over here and then the next to Cairo carbons have both of their hydroxyl groups or have their hydroxyl groups pointing to the left, which corresponds with l configurations so we can put two l's here. And so the real question is, how do we determine the configuration of an entire mono sacha ride if it contains a mixture of configurations, a mixture of D and L configurations? Well, really, that's what these next two bullet points are addressing right here. And so a mono sacha ride will have the same exact configuration as the configuration of the highest numbered Kyra all carbon. Or, in other words, to say the same exact thing. We can say that a mono sack rides configuration is going to be that of the Cairo carbon that is furthest from its Carbonnel group. And so if we take a look at this glucose and anti armor right here, notice that it's Carbonnel Group is way up here at the top in this alga hide group. And so the Cairo carbon that is furthest away from the car bottle group is gonna be this Cairo carbon right down here. And so that means that the configuration of this entire mono sacha ride is going to be the same of this Cairo carbon. That's for this away, which is a D configuration. And so that means that this entire glucose and aunt humor is the D glucose and anti humor. Now, if we take a look at this other an anti moreover, here notice that it's Carbonnel Group again is at the very top. Uh, here in this out of High Group and the Carbonnel Group, the Cairo Carbon that's furthest from this carbonnel group is this one right here? And so this one has an L configuration, which means that this entire Manu sack right here will also have the L configuration. So this will be l glucose. And so, really this you'll be able to get a good hang of how this works. As you start to get more practice so moving forward in our course, we will definitely be able to apply these concepts in practice problems. Now, the last thing that I want to leave you guys off with is that unlike biological amino acids, which we know from way back in our previous lesson, videos are usually in the l configuration biological carbo hydrates. On the other hand, they tend to usually be in the D configuration. And so the rial reason for why life prefers l amino acids, but it prefers d carbo hydrates is unknown. And so there are some theories, but we're not going to, uh, cover those theories here. But what you do need to know is that life prefers D carbohydrates and life prefers l amino acids. And of course, there are some exceptions. But for the most part these are the preferences. And so this concludes our lesson on Fisher's projection and how to determine d l configuration. And again, we'll be able to get some practice as we move forward in our course. So I'll see you guys in our next video.