 Okay, so you want to do this problem there? Okay, chloramphenicol is a broad spectrum antibiotic that is particularly useful against typhoid fever. What is the configuration of each asymmetric center in chloramphenicol? Okay, so let's do this one. So you can see here, hopefully, remember that we're looking for stereocenters here. So what is the stereocenter? It's a carbon that's got four different groups attached to it. So if we look here, right, we can see, let's point out all the carbons. So carbon, carbon, carbon, carbon, carbon, carbon, remember, wherever there's a point, that's a carbon, right, every two lines intersect, that's a carbon. So obviously, carbon, carbon, carbon, carbon, carbon, and that's it, okay? So which ones have four different groups attached to it? So this one has two hydrogens attached to it, so already, not four different groups. This one has a double bonded to an oxygen, so it doesn't even have four groups attached to it. So you have to have four groups attached to you to be a stereocenter in the beginning. This carbon is attached to two hydrogens, not a stereocenter. This carbon seems obvious that it's a stereocenter, but let's just see. So we got it attached to a nitrogen, so that's different than a carbon, which is different than a hydrogen, okay? So there's three groups, and then we got a carbon over here. So carbon and carbon are the same, right? But this carbon is attached to two hydrogens and an oxygen, okay? So if you can't see that, you might want to draw that out. So it's attached to two hydrogens and an OH group, okay? So this carbon over here is attached to an OH group and a hydrogen, so OH and hydrogen, but it's attached to a nitrobenzene group, too, instead of another hydrogen. So these two groups are actually different, right? So that carbon there is what we know is known as a stereocenter, or I guess an asymmetric center. What this book is going to do, same thing. Okay, so let's just draw it back, C, H, 1, 2, okay? And then let's keep going, see if any of these other carbons are. So this one, well, we know that those three are different, and this carbon is attached to all these different groups. We just figured out that those groups are different, of course, than these ones. So this is going to be another stereocenter. So you've got two stereoceners in this molecule so far. So carbon, is this carbon attached to four different things? No, it's sp2 hybridized, so it's not attached to four different things at all, it's just attached to three different things. Same thing with all of these carbons. And in fact, that's the case with all carbons on a benzene ring, benzene type ring. Okay, so let's go ahead and address the stereochemistry of these two stereoceners then. Okay, so what do we've got here? So let's start over here. So remember, we have to assign priority to these stereoceners. The highest priority is going to be the atom that is located highest on the periodic table or with the highest atomic number, if you will. And of course, the lowest atomic number will be the lowest priority. So if you've got a hydrogen on there, it's always going to be number four. Okay, so we could put four there already. So now we've got to choose between nitrogen, carbon, and carbon. Well, nitrogen is bigger. So that's going to be number one. Okay, so that's the highest priority because it's bigger than carbon, carbon, and hydrogen. And now we've got to decide between these two carbons, which one's bigger? Well, this carbon's attached to hydrogen, hydrogen, and oxygen. This carbon's attached to a hydrogen, oxygen, and carbon. So this one is actually bigger because carbon is bigger than hydrogen. Okay, so we've got two and three. So hopefully you can, oh yeah. And then the next thing you want to do is put the lowest priority group in the back. We're in luck because in this case it's already in the back, okay? So now we just go and do our little rotation arrow like we've done. So here we're going one, two, three. So in this case it's going clockwise. So clockwise is R, remember. So this stereocenter over here is R. Okay, so let's erase those little numbers so we don't confuse ourselves while we're doing this other stereocenter over here. So we want to prioritize just like we did before. So hydrogen, always number four if it's there. Oxygen's bigger than carbon and carbon, so oxygen's going to be number one. So this carbon and this carbon we have to decide which one's bigger. Well, this carbon's bonded to a nitrogen, okay? And this carbon, I mean, sorry, this carbon is bonded to a carbon, a carbon and a carbon, okay? So although three carbon seems to outweigh a nitrogen carbon and hydrogen, because hydrogen is so small, all we're really concerned about is the biggest one, okay? So which one trumps which one? So nitrogen or carbon, well, nitrogen's bigger than carbon, okay? So we got one, now this is going to be two over here, and this one's three and four, and we're in luck again with a gracious problem. So we do the same thing, one, two, three, okay? And this one is also going clockwise. So in this case, they're both R. So you could write this molecule's name as RR, whatever, whatever the IUPAC name of this molecule would be. You could figure it out if you want to. Okay, does that answer your question? Okay.