Atropisomers

Hey, everyone. So now that I know in general terms how to predict what types of stereos summers they're gonna get based on the number of Cairo centers Now I want to start teaching you some of those exceptions to the rules. And the first of those exceptions is a Cairo compound that doesn't have any Kyrill centers at all. And these air called a TRO by summers. Okay, so H o by summers are these unusual compounds that contain no Cairo centers. Yet they actually are Cairo due to their inability to freely rotate. Okay, now it really depends class by class, Professor by Professor, How much emphasis they put on these compounds because they are unusual and they're not ones that we deal with a whole lot in or go one. Okay, but sometimes you Professor might just throw these in as a trick so that you'll forget about these kinds of compounds that can't rotate. Okay, so here I have just a few. In fact, there's a few more, but this is a really common ones. So Allen's, as you can see, a lines there to Dole wants together. They can't rotate because the old ones can't rotate substituted by finals. I know you don't know what that is yet, but a by final, just two federal groups that are attached in one spot and they're substituted meaning that they can't really rotate because those substitutes that you can see sticking out, kind of act as teeth, they lock it together so it can't fully rotate. Okay, Trans cyclo OC team. This is actually a molecule that I was just recently talking about, how it conform the CIS version and the trans version. It turns out the trans version, because it can't rotate it can actually form a right handed version of this twisted messed up thing and a left handed version so very peculiar looking molecule. But it was also Cairo because of lack of rotation. Then finally, by an app which I don't even remember exactly what it stands for. But it's very similar to the substituted by fennel, where, except in this case, one an entire fennel group or an entire benzene ring is acting is one of those teeth. That's not gonna let it rotate across that single bond. Alright, so all of these are going to be Cairo, even though they lack Carol centers. Thes air. Like I said, this is not the usual. This is This is not the norm. These air unusual molecules that happen to display Kyra Ality.

So what I wanna do is I want to teach you guys tests for the two most common ones which are aligns and substituted by Faneuil's and the other ones don't really need rules. So you're fine. You could just always assume that they're gonna be Kyle. But it turns out Allen's and succeeded by finals can be Cairo, or they cannot be Tyrell, depending on the rules that they follow. So let's look at this. So what we're gonna do is we're simply gonna use test of modified version of test to which is the one that for stereo centers toe identify tribunal centers in the alley. Okay, but you're going to say Okay, but there's two double bonds. Which one do I look at? Well, this is the ghetto part. We're going to visualize the Allen as just one big double bond. Okay, so maybe, like, squint a little bit and try to see that. Try to ignore the carbon in the middle and just pretend that it's one big double bond. Okay, this is by the way, this is just my way of solving these, but I think it helped a lot of students, and I think will help you guys okay If it's able to form E or Z Ice Summers after visualizing it as a big double bond, that means that it's Cairo. Okay, so remember that when I taught you guys about tribunal centers, I told you that they're actually a Cairo Okay, if they pass the test but Allen's air different. So just think about aliens is their own thing. Allen's You're gonna be Cairo if they conform ears e through this weird long double bond. So I'll do the first one with you guys and then I'll let you guys do B and C on your own. So what I would do here is I would look at this compound and I would just ignore that. See, in the middle, I just pretend that it's one big double bond. Okay, then I would ask myself, Is this Dole unable to form cysts entrance? Or is it able to form E and Z? What do you guys think? According to my rules for double bonds, this actually cannot form E and Z or assistant Trans, because I have two of the same Adam on one carbon on one side. So that means that No matter how much I switch these two groups, I'm never gonna be able to get E and Z. So this one would be a Cairo. Okay, so now what I want you guys to do is I want you guys to solve, be, and then I want you guys to solve scenes.

All right. So B is going to be Cairo, Okay? And the reason it's going to be Cairo is because if I visualized this as a big double bond Okay, then what I have is that none of the carbons have two of the same group on them. So that means that if I were to draw my fence here, my methyl groups could arrange in two different ways. This would be that they're both in the same size. This would be the cyst confirmation. But I could also have a situation where my Alan looks like this. Where I have my c h three on my H. But then my ch three is over here, and my h is back here. Okay? And that would be the trans version. Okay, Now, like I said, is this chemically accurate? Not really, but it's gonna help you guys thio figure out which ones are Cairo or a Cairo. All right, so this one would be Cairo. Go ahead and try to do so

So hopefully you said that C is a Cairo. Okay, because see, if you visualize it as a big double, Bond has two of the same group on one side. So that means that no matter how much I rotate these guys here, no matter how much I flipped them, I'm always gonna have the same compound. So this one again, since as two of the same thing just like this situation over here, which is a bad situation, they're both going to be a Cairo because they can't form system trans. Alright, So it was easy, right? So now what I want to do is move on to substituted by finals.

so these guys are gonna have a pretty weird rule to basically for subsided biphenyls. What we look at is the substitutes in the Ortho position. Now, Ortho was a word we're not really gonna use until or go to very much. But just as a heads up, what it means is next to or adjacent to. Okay, So basically we're looking at is the substitue INTs that air next to that single bond or that Sigma Bond that it's rotating around. Okay. And what I want to do is I want to figure out if any of the rings have two of the same group. If they have two of the same group, then it's not Cairo. But if it has, if if they have, it basically has to the same group, then that's going to be a Cairo, Okay, but it has two different groups. Then it's fine. Then it would be Kyra, similar to the way that we did it for aligns. Okay, so let's go ahead and do a together, and then I'll have you guys do B and C on your own. So, for a do, I have two of the same groups on any of the rings in the Ortho position. And the answer is no. These groups are different, and these two groups are different. So I mean, this is gonna be a Cairo substituted by federal because of the fact that these groups none of the rings have two of the same exact thing on one side. Okay, so go ahead and try to figure out B and C.

Alright, be is a Cairo. Why? Because it has two of the same group on one of the benzene rings. Okay, just you guys know this is a group that we're not going to deal with? A lot of Orgel one. This is called a nitro group. Okay, Just introducing it. In case you guys, you're probably going to see it in order. Go to Okay, So Nitro Group. But there's two of the same one, so it doesn't matter how weird it is. If there's two of the same thing, it cannot form assistant Trans. That would be a Cairo. Let's move on to see

So I'm gonna take myself out of the screen here so you guys can see everything. So in this case, do I have two of the same group on this molecule on on any of these rings? And the answer is no. This one. I have two different groups. This one. I have two different groups. So all I'm looking at is I don't have to the same ones. So this one would be Cairo. Okay. So hopefully that made sense to you guys and let me know if you have any questions on a tro Py Summers remember that these air like a specific subset of molecules but are not the norm. So you should really use the generals that I told you about. If it does not have a Carl center, assume that it's a Cairo unless it's one of these four guys that I talked about. All right, so let's go ahead and move on to the next topic.