3D decalin TBR OChem: Chapter 2, passage 1, question 7

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monkeyMD

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I don't understand how to convert the given form into the chair form.

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Do you still need help on the problem? What about it don't you understand? Is it just decalin or does it have substituents?
 
I don't understand how to convert the given form into the chair form.

What I did was to first draw the right ring in chair conformation. The I added both of the Hs up (one being axial and one being equatorial, because that's how neighboring Hs that are cis must align). This means that the ring on the left must be connected to the ring on the right with one equatorial bond to C and one axial bond to C. That's what leads to the weird looking structures in choices C and D. To help see this, draw the Hs on the two shared carbons in choices C and D, and you'll see that they are both up (with the one closer to the OH group being axial and the other one being equatorial).

The placement of the OH group is just a matter of seeing that up would correspond to axial when it's two carbons away from the axial H on the shared carbon.

Hopefully that helps.
 
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