Cycloalkane's

[DrRoyal Pains]

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When given a question regarding something in the chair conformation, is it just easier/faster to draw the structure out as the actual cycloalkane it is (in the planar conformation)? For those of you with subscriptions to Chad, you can see the problem in O2.3.

 

[FROGGBUSTER]

I don't think it matters, not many people run out of time on the Sciences section.

 

[radmazindds]

I have a great method for this. Hopefully it can translate well through this post.

First draw a cyclohexane (flat, not in chair form) with all your substituents with the proper wedging (cis/trans/R/S, whatever it may be). On any arbitrary carbon of the cyclohexane, write down "E/A." Going clockwise (or counterclockwise, it's arbitrary) label each of your cyclohexane carbons "A/E" "E/A" "A/E" alternating until you have them all labeled, like this:

Then find your highest priority substituent and assign it "E" (this is usually the case) for equatorial. Then, if anything is CIS to that, assign it with whatever letter is on that side of the slash. If anything is TRANS, it will be to the other side of the slash.

I made up a molecule and worked it out as an example:

Hope it helped! good luck! this might've been confusing so let me know if u want me to clarify.

EDIT: heh... I guess I didn't read ur question carefully...

When given a question regarding something in the chair conformation, is it just easier/faster to draw the structure out as the actual cycloalkane it is (in the planar conformation)? For those of you with subscriptions to Chad, you can see the problem in O2.3.

 

[DrRoyal Pains]

Thanks man. That is a good strategy, and it looks very helpful. I just wanted to know if it was a good method to do so, and I can see it is. Thanks again.

I have a great method for this. Hopefully it can translate well through this post.

First draw a cyclohexane (flat, not in chair form) with all your substituents with the proper wedging (cis/trans/R/S, whatever it may be). On any arbitrary carbon of the cyclohexane, write down "E/A." Going clockwise (or counterclockwise, it's arbitrary) label each of your cyclohexane carbons "A/E" "E/A" "A/E" alternating until you have them all labeled, like this:

Then find your highest priority substituent and assign it "E" (this is usually the case) for equatorial. Then, if anything is CIS to that, assign it with whatever letter is on that side of the slash. If anything is TRANS, it will be to the other side of the slash.

I made up a molecule and worked it out as an example:

Hope it helped! good luck! this might've been confusing so let me know if u want me to clarify.

EDIT: heh... I guess I didn't read ur question carefully...