 Okay, so let's try this problem together. It asks us to assign SNR configuration to each stereocenter in the following molecule. Okay, so remember this is a fissure projection. Remember, we mill fissure way back when deciding to write these structures to indicate the carbon atoms and sugars. Okay, so this is a common projection that you will see, a common structural representation that you will see, especially in your biochemistry books. Okay, so it's good for us to be able to take this representation and put it in kind of bond line or expanded form. Okay, so that's what we want to do right now. So I want to recall that anytime we have these wedges, that means that these bonds are coming out of the plane of the board, okay? Anytime we have a hash bond that's going behind the plane of the board and anytime we have just a straight line that's in the plane of the board, okay? So now I want you to take this structure and I know you all have been working on it already and put it in an orientation that looks more like the bond line forms that we've been drawing so we can figure out R and S forms, okay? This one's really nice because both the hydrogens are on one side so we can stick both of those hydrogens in the back really quick, okay? So that's what I'm going to do right now. First I'm going to draw the two carbon atoms. So those are the two carbon atoms in the plane there. Okay, everybody okay with what I've done so far? Yes. Okay, wonderful. So now hopefully you can see what I'm going to do is take this structure here with this OH of this methyl group forward and I'm going to take it and make it like this, okay? So we'll see both the OH and the methyl group forward, okay? So you can do something here. Let's build this molecule. This molecule is the same molecule as this but it doesn't have the hydrogens on the methyl groups and the OH, okay? So hopefully everybody can see, bromine is purple, OH is red, the two hydrogens there, methyl group and methyl group there, okay? So what we're going to do is take it and move it like that, okay? So, H in front, methyl group in front, and in the back we're going to have the two hydrogens. On this carbon atom we're going to have a bromine going down and on the other carbon atom we're going to have that methyl group. Okay, so like I was saying, this is a really nice structure of representation to put it in because you have the hydrogens in the back already and the hydrogens are the lowest priority of the groups, okay? So to have a stereo center we have to have four different groups on a particular atom. Hopefully you see we have four different groups so we're going to call that a stereo center. Same thing over here. This carbon atom has a hydrogen, a hydroxyl, a methyl and this group over here, okay? So that's four different groups on another stereo center. Okay, so now we're going to come to the crux of the problem and identify whether these stereo centers are R or S, okay? Like I said, the cool thing is since we have the lowest priority in the back we don't have to rearrange this molecule, okay? It's already in the confirmation that we want to identify whether it's R or S. So, help me out. What's bigger? Bromine, carbon or carbon? Well, that's one, okay? What's bigger, carbon or carbon? The same, yes, exactly. I like that face, yeah. Instead of not, I don't understand. He's like, what, are you crazy? They're not different. I love it, that's awesome. So we've progressed so far just in the last couple hours. Okay, so carbon and carbon are the same, right? What's next over here? Hydrogen, right? And oxygen, which one's bigger? Oxygen. So this is going to be two. And since this is the only one left over, that's three, okay? So let's see if we can get this right. That's going opposite of the way of the clock, right? So, like that. So that's going to be S, right? Okay, so let's do the same analysis over here. Is everybody okay with what we've done over here? I guess I should ask. Everybody cool? Okay, wonderful. So here, hydrogen's already in the bag. We don't have to worry about it, right? So what's bigger? Oxygen, carbon or carbon? Oxygen. Oxygen. One, okay? Carbon or carbon? Same. Hydrogen or bromine? Bromine. So two opposite of the clock, right? So counterclockwise. So that's also S, okay? So if we were to label this, we would say this is the S, or stereois. Okay? Any questions on that? If you rotated the wrong way, you would get the wrong way. No, no. If you rotated it the wrong way. If you get the wrong way. No, no. You still have to put the thing in the bag, the least priority group in the bag. So if that's not the case, you're going to have to rotate it again to be able to do that. I understand, okay? So are there any more questions? Okay.