Equatorial Preference - Video Tutorials & Practice Problems
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Determining the Best Position
1
concept
Equatorial Preference
Video duration:
4m
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Video transcript
the equatorial preference has to do with the fact that one of the two positions remember that there's the actual position and there's the equatorial position. One of them is going to be much more crowded or what we call Torshina Lee strained than the other Now, usually, if you just have hydrogen is in there, it's not a big deal. But if you start adding bulk your groups in there, it's actually gonna affect it. Okay, so let's just look at the different positions. Remember, we have our actual positions. They're going straight up and down with the corners. Remember that we have our equatorial positions going slightly opposite. Are you guys cool with that? So far and now, let's imagine that I put different shapes here. So let's say that I just put a bunch of maybe like green circles on the equatorial positions and let's say that I put like some blue balls. Oh, man, that's just got really weird blue circles on the axial physicians. That sounds like it hurts. So we've got these ones on the positions and I just want to analyze the ones at the top. Let's just say that we look at this blue circle, this blue circle and this blue circle versus this, um, green circle, this screen circle and this green circle. Alright, guys, following so far. In fact, let's go ahead. You don't have to do this, but I'm just gonna erase the other ones, too. You guys don't get distracted, so you can really see what's going on here. See? So that's how clear I want it to be. So basically, we've got our actual positions and our equatorial positions. Which of these do you think is gonna be the most spread out? And then which of them is do you think is gonna be the most take together? And it turns out that it's going to be the blue balls are, like, really close together. Okay, so it's, like, awkward and stuff like, You do not want to be there. All right. On top of that there, like sitting on sticks. It's terrible. So whereas the equatorial positions, they've got all this room to spread out, it's awesome. Look how far apart they are. Okay. In fact, if you want to think about the equatorial position, it kind of looks like it's the equator of the Earth. If this is like a big globe, the equatorial positions would be like on the equator. The actual positions would be like on the North Pole, alright. And the South Pole. So you don't want to be stuck on the South polar North Pole? You wanna be like in paradise, like on an island drinking a corona. Okay, so the actual positions suck. That's what I'm trying to say, Especially when you put large groups there. You do not want to be in the actual position. So what that means is that the ring is always gonna flip in order to accommodate the preference of the largest substantial. So in this case, I have a Turk beauty group, and that's her Beetle group conform. It could be on two different shares. It could be on one chair that has it in the axial position. But any time that you flip a chair, you wind up flipping positions. Okay, so if you flip your chair, you also wind up flipping positions. So now this would become equatorial over here. All right, so it goes from actual equatorial. Which of these do you think is gonna be the most stable? And it turns out that it's gonna be way more stable in the equatorial position. In fact, over 99% off this compound is gonna exist in the equatorial position and less than 1% is going to exist in the actual position. Why? Because the axial is so much more torch innately strained with these h is here. See, they're just bumping into each other, whereas as the equatorial position is way better. Okay. So, as I just said, when chairs flip, remember that axles are always gonna become equatorial and equatorial has become axel. Okay, so any time you flip, you're going to be giving something in the actual position, an opportunity to become equatorial. But you also have to change the shape of the chairs well.
Blue = Axial. This position sucks, it’s really cramped up. Large groups can’t stand it.
Green = Equatorial. This position is awesome. Large groups want to flip to this position.
Determining Equatorial Preference
We always want to draw our chairs with the largest groups equatorial. If they are axial, we need to flip the chair.
2
example
Draw the following chair in the most stable conformation.
Video duration:
3m
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Video transcript
So what I want you guys to do is look at the following molecule and analyze if it's in the most stable position. In fact, don't even analyze it. I'm ready telling you it's not in its most stable confirmation. Can you tell me why it's not the most stable? Because what I have is this. I have an actual position and I haven't equatorial position. Right? I have two different groups. I have a big group and a small group. Okay, no matter what. If I flip this molecule, I'm always gonna have one equatorial on one axle because the equatorial becomes Axl and the actual becomes equatorial. So no matter what, I have to have one of them in the actual position. Do you agree with me? At least something has to be axle. But right now I have the wrong group in the actual position. I have a big group. Instead, I should have the small group in the actual position. So we want to do is we want to draw a chair flip to accommodate the equatorial preference. What that means is that I want to show that I'm gonna draw the opposite chair and then I'm going to draw the ch two ch three now in the equatorial position. So what that means is that I want to draw a chair that has this corner facing down, so I'm gonna draw it like this. Okay, so now what that means is that this corner, basically, I had these were three carbons away. Or, like, one. And in, if this wasn't my number one thing, this would be too. And this would be three. Well, now I'm gonna make that this is my one. Which means that 23 my three would be over here. Okay, So what that means is that now, this equatorial position that was a metal on the three is now gonna be actual facing down? Why is that? Because remember that the actual position always follows the corner. In this case, the corner is facing down. So I would put it there. Okay. And now, since my number one is here, I would now face this one equatorial, and this would actually be Let me take myself on the screen for a second. This would be a much more stable confirmation. Why? Because of the fact that you're gonna be able to have the larger group, the bigger group in the equatorial position on the smaller group in the in the actual position. All right, so some of you guys might be wondering, Johnny, But how do you know to pick those carbons? So, for example, let me see if I can add myself back. All right, There we go. So some of you guys might be wondering, Johnny, why didn't you go around the other way? Why didn't you say that? Why didn't you say that this was your to And this was your three and then draw the ch three here, and honestly, it doesn't matter. In fact, I'm gonna have an entire section where I'm just going to talk about how those two chairs of the same thing. And it doesn't matter exactly how you draw it as long as you're being consistent. Okay. But just, you know, it would still give me the same thing where the stage three would be axial. The Ethel would be equatorial, and this one's way more stable. All right. And you should be used to drawing. You should get used to drawing chair flips because some professors really want you to be able to do that. All right, so let's go ahead and move onto the next topic
Don’t worry about drawing this problem out correctly on the first try, as long as you know how to flip it to the correct chair, that’s all that matters.
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Problem
Problem
Draw the MOST STABLE conformation of cis-1-tert-butyl-4-methylcyclohexane.
A
B
C
D
Hint: If you don’t know what neopentyl is, it’s ok. Obviously it has 5 carbons, so keep that in mind when deciding equatorial preference!
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Problem
Problem
Draw the LEAST STABLE conformation of trans-1-tert-butyl-3-neopentylcyclohexane.