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Help with Chair Formations on Cyclohexane!!

Hi,

I'm confused by chair conformations: especially when it comes to cis/trans,

below I have attached an image of the molecule cis-1-chloro-3-methylcyclohexane, they are both the same conformer...



I'm confused which is supposed to be the cis molecule as in both molecules the two priority groups are either both pointing up or both pointing down; I know that the first molecule is favoured as the larger groups are in the equatorial position does that mean the correct drawing is the first?

Any help would be greatly appreciated,

Cheers
Original post by okaythenoneone
Hi,

I'm confused by chair conformations: especially when it comes to cis/trans,

below I have attached an image of the molecule cis-1-chloro-3-methylcyclohexane, they are both the same conformer...



I'm confused which is supposed to be the cis molecule as in both molecules the two priority groups are either both pointing up or both pointing down; I know that the first molecule is favoured as the larger groups are in the equatorial position does that mean the correct drawing is the first?

Any help would be greatly appreciated,

Cheers

cis- means that the two attachments are on the same side of the ring system.

Once you have drawn the chair (most stable conformer) there are three axial bonds that point vertically down and these are cis- to the bonds on the intermediate carbon atoms that look equatorial.
Original post by charco
cis- means that the two attachments are on the same side of the ring system.

Once you have drawn the chair (most stable conformer) there are three axial bonds that point vertically down and these are cis- to the bonds on the intermediate carbon atoms that look equatorial.

Okay thank you I think that makes sense... just to double check this means that the molecule is cis with respect to the axial bonds that point down, so molecule one is the correct drawing and number 2 isn't?
Original post by okaythenoneone
Hi,

I'm confused by chair conformations: especially when it comes to cis/trans,

In the diagram, all of the blue bonds are axial, and all of the black bonds are equatorial.

The 1,2 blue bonds are trans to one another.
The 1,2 red bonds are trans to one another
The 1,2 red-blue pairs are cis- to one another.

chair.jpg
(edited 1 year ago)
Original post by charco
In the diagram, all of the blue bonds are axial, and all of the black bonds are equatorial.

The 1,2 blue bonds are trans to one another.
The 1,2 black bonds are trans to one another
The 1,2 black-blue pairs are cis- to one another.

chair.jpg

So in this example for the 1,2 bonds, for any given molecule with 2 substituents that aren't that sterically hindering, if you were asked to draw the 1,2-trans molecule would you draw it as the axial bonds being trans or the equatorial being trans to one another? Sorry if I'm just going in circles...
Original post by okaythenoneone
So in this example for the 1,2 bonds, for any given molecule with 2 substituents that aren't that sterically hindering, if you were asked to draw the 1,2-trans molecule would you draw it as the axial bonds being trans or the equatorial being trans to one another? Sorry if I'm just going in circles...

If you draw the 1,2 axial attachments as trans- there will be little steric interaction, unless there are bulky axial groups already on the ring.
Original post by charco
If you draw the 1,2 axial attachments as trans- there will be little steric interaction, unless there are bulky axial groups already on the ring.

given that the groups were small could you also draw it as 1,2 equatorial trans?
Original post by okaythenoneone
given that the groups were small could you also draw it as 1,2 equatorial trans?

yes

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