Draw two different chair conformations for each of the followi...

Question

Draw two different chair conformations for each of the following molecules. Make sure that your drawings clearly show the cis–trans stereochemistry.

(c)

Accepted Answer

Welcome back. Everyone. Here's our next problem. It says sketch the chair confirmations for the compound shown below label the structures as cis or trans. And we have a Cyclohexane ring and we see at the opposite position. So one and four, we have a Bromine substituent which is drawn with a solid wedge. So it means it's coming up out of the plane of the paper towards us, out of the plane of the screen and on the opposite side, then position four a Corine which has the dashed wedge, meaning it's projecting down behind the plane of the screen. So away from the viewer. So note, it asks us to sketch the sketch, the chair confirmations plural. So that means we'll need to draw one and then flip the chair confirmation. So it says label the structures of cysts or trans. But we can tell that even before we draw a chair because we see that our bromine is coming up towards us, our chlorine is going away, they're pointing in opposite directions. So substituents in opposite directions or we can say our substituents are on opposite sides of the ring. So they are therefore trans to each other. So both of our chair confirmations are going to be trans structures. Since when we draw the flipped chair, we switch whether the substituents are actual or equatorial, but we keep their orientation with respect to the ring, either up or down. So it will still be trans in both chair confirmations. So that's important. So let's go ahead and draw one chair. So in this case, then you can start either way, I'm just happening to start with two parallel lines pointing up into the right. Let's make that a little shorter and then add my two ends here. So I'll add Bromine, I need Bromine to be pointing up with respect to the ring. So I will make uh and again, I'm going to number my ring recall that by naming convention, Bromine would be on carbon one. The two are both halogens or equal in priority. So we go by alphabetical order. So I'm going to take a moment and go back to my ring drawing and label the carbon. So Bromine's on carbon one around 23 chlorine and carbon 456. That's important because we need to make sure we're going clockwise or counterclockwise, whichever our original structure is. So we see in our just flat plane structure starting from Bromine, we're going in a counter clockwise direction as we number the substituents. So we have to maintain that. So I've got my chair confirmation and I just tidied that up a bit as I didn't like the way it looked. So again, we know Bromine has to be pointing up. So I'm just picking the back right of my chair structure. So kind of the highest point, I guess you might call it. And at this point, the uh position that's going to be pointing upward is the axial. So that will be Bromine pointing straight up as in an axial position. But again, upward, with respect to the ring. Now, we could start anywhere as long as we maintain the distance apart of our substituents, we maintain how, so how many carbons are they apart and maintain their up or down orientation with respect to the ring and then whether it's numbered clockwise or counterclockwise. So now we know we need to number it counterclockwise. So Bromine will be number one, we'll go in that counterclockwise direction to name our other carbons 3456. We know the chlorine is on carbon four and that it points downward. So again, carbon four being a downward pointing part of the ring, that would be an axial substituent also pointing downward, the equatorial positions uh in each case or in the wrong direction. So on carbon one, equatorial position will point upward, excuse me, point downward and on carbon for the equatorial position will point upward. So we've got our first chair confirmation numbered, counterclockwise, Bromine and chlorine both in axial positions and Bromine pointing upward, chlorine pointing downward and we see as we said, this is the trans structure and now our flips chair, so we'll draw our chair going in the opposite direction. So now we need carbon one. It was on sort of an upper part of the chair. We now need it to be poured on a lower part of the chair. So we'll label carbon one, this one on the bottom, right? Harbin one has our Bromy. It needs to be facing upward with respect to the ring. So in this case, that will be in an equatorial position, which makes sense. Since again, when we do the chair swp chair flip, we should be switching axial to equatorial and vice versa. So we have Bromine here. It's in the equatorial position now, but that still leaves it pointing upward. Now, let's label in a counterclockwise direction. Carbon 2345 and six are chlorine's on carbon four. It still needs to point down. But now that is going from axial to equatorial. So again, that will be an equatorial position but pointing downward. So again, both maintain they're both trans pointing in opposite direction. The ring is numbered counterclockwise. Bromine is pointing upward. Chlorine pointing downward, but they flipped from axial to equatorial position. So that is our two chair confirmations the chair and the flipped chair and they both are in the transformation. See you in the next video

Draw two different chair conformations for each of the following molecules. Make sure that your drawings clearly show the cis–trans stereochemistry.

(c) <IMAGE>

Key Concepts

Chair Conformation

Cis-Trans Stereochemistry

Stereoisomerism

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