Organic Chemistry

Learn the toughest concepts covered in Organic Chemistry with step-by-step video tutorials and practice problems by world-class tutors.

4. Alkanes and Cycloalkanes

Everyone draws their chairs different. How do you know if yours is right? 

Determining Which Chairs are Equivalent



The 3 important factors when drawing chairs

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So I found that one of the hardest things about teaching this section as a tutor is that everyone draws their chairs differently. So some of you guys are gonna have, like, these really bubbly chairs, and some of them are gonna be really flat. Some of them are just gonna be ugly. Some people are gonna want to draw the left hand chair more and some people going to draw the right hand chair more. And what that means is that I'm going to get I get inundated with lots of questions. Johnny is my chair the same as yours, or did I draw the right chair? Okay. And that's why I created this whole new section that isn't in your textbook just to explain to you guys what's important about comparing chairs. Okay, Because it turns out that there's hundreds. There's probably hundreds of different ways to draw the same chair. Okay. And they're all right. You just have to figure out what's important so you'll know what to look for and what is what you can ignore. All right, So when we're drawing equivalent chairs, Okay, What we wanna worry about is just three things, okay? Your your chair could be to the right. My chair could piece the left. Yours could be upside down. Yours could be way more flat looking than mine. But there's only three things that really matter. The three things that matter are the distance between the groups that has to do with how far they are from each other. If the first one is on your one position is your second one next to it, That would be called 12 If if they're two carbons apart, that would be called 13 If the three carbons apart, that would be called 14 Either way, those really the those are the three different combinations of having two things. But either way, if as long as the distance is the same, we're already off to a good start, the next important thing is CeCe versus Trans. So maybe you wrote one equatorial when I wrote one axial. But in the end of the day, if they if the system trans is the same, then that's also going to mean that these were gonna be the same chair. Okay, so what that means is that if I drew a one to sis upside down and usual, one to cysts on some different carbons. There's still the same molecule because overall, the distance is the same. And assistant transit the same. Okay, then for chairs that are asymmetrical, meaning that they have two different types of groups than equatorial preference is important, too. Because maybe I drew the same Cheras you. But I drew the other conform. Er, maybe I had a 12 cysts and you had a 12 assists. But you drew it with the big group in the axial, and I drew it with a small group in the axial. Are those identical? Well, they are the same molecule, but they're called conformers. Remember that they their equilibrium for in each other with each other. Okay, those are three things that we look for. So what I want to do here is you know what? I'm actually going to do a free response one just as conceive what? I mean, Okay, so imagine that I'm drawing an answer. And I told you guys that the right answer is ch three here and ch three here. Okay, So I tell you guys that that is what the answer is supposed to look like. But the thing is that you draw chairs differently than me, and you like to draw the other chair. So you were drawing the other chair and you draw a little bit different. And what you drew as you're right. Answer was actually, um a c h a c h three here. Okay. And then you drew a ch three. Let me see. And then you drew a ch three here. Okay, so basically, this is my answer. I said, this is the right answer. And then this is yours, and you're thinking, Wow. Did I draw this right? Do I have the right answer, or am I just completely wrong the way that we would compare these is instead of freaking out and saying I must have gotten it wrong? I don't know what I'm doing. Instead of freaking out, just say okay. Is the distance the same? Is the system trans the same? Okay, so, first of all, what's the distance between these two groups? Well, if this is my one, you can pick anything to be your one. Then this will be 234 So this is gonna be a 14 dimethyl Okay, Now let's look at yours. Because this is the one that you drew. So you wrote 1234 Look at that. You also drew a 14 dime, Ethel. All right, So you weren't that far off. Now let's look at the system. The trans this one, they're both facing up. So this one was sis, This one. They're also both facing up. So this one was cysts. So guess what? These are the same compound. They're drawn differently, but they're the same compound, so both of them are correct ways to draw this. I know one just looks more messy, and one looks still kind of messy. But at the end of day, there the same thing. And that's what I'm trying to help you guys see, because I get asked, all these kind of questions is mined the same as yours. Okay, so let's go ahead and do some practice identifying the following chairs. Are they identical? Conformers or different. So go ahead and try to answer this and then go to the next video. Once you think you know

There’s only 3 things that you have to keep track of when you draw a chair.

Distance between groups

Cis vs. Trans

Equatorial Preference (determines conformers)

As long as these factors are the same between chairs, they are the same, regardless of what they look like!


Determine if the following pair of chairs are identical, conformers or different.


Determine if the following pair of chairs are identical, conformers or different.


Determine if the following pair of chairs are identical, conformers or different.