[__alibaba__]

I have been having a bit of trouble with the chair formation of cyclohexane and trans and cis groups. In specific, I am having a hard time figuring out when a molecule that is trans has groups extending out equatorially or axially.


For example, in trans-4-Methylcyclohexanol, how do we know that the methyl group and the alcohol group are both axial and equatorial?

Then, in cis-4-Methylcyclohexanol, one group is always equatorial while the other is axial. It seems like the cis and trans molecules should swap where their functional groups are.

Does it have something to do with the imaginary plane that splits the molecule into an upper and lower half?

[Ben Bob2]

In specific, I am having a hard time figuring out when a molecule that is trans has groups extending out equatorially or axially.

They key with these problems is that less strain occurs when the most substituents, and/or when the largest substituents are in equatorial positions.

For example, in trans-4-Methylcyclohexanol, how do we know that the methyl group and the alcohol group are both axial and equatorial?

Always start by drawing the skeletal structure with dashes and wedges, and then draw the "chair" picture adding the substituents at the very last step. In this case, the substituents are on exact opposite ends of the ring and, as you said, are trans, so how many conformations can it have? Which is more stable based on what you know about substituent size?

Then, in cis-4-Methylcyclohexanol, one group is always equatorial while the other is axial. It seems like the cis and trans molecules should swap where their functional groups are.

I don't think I quite follow what you are saying about swapping functional groups. Maybe you could try drawing this with the forum software. Just remember that the largest group will be in the equatorial position.

[__alibaba__]

Always start by drawing the skeletal structure with dashes and wedges, and then draw the "chair" picture adding the substituents at the very last step.

Ah! That helps a ton. Thanks!

In this case, the substituents are on exact opposite ends of the ring and, as you said, are trans, so how many conformations can it have? Which is more stable based on what you know about substituent size?

It can have two conformations. One where the two substituents are equatorial and one where they are axial. The conformation where they are equatorial is favored.

[Ben Bob2]

It can have two conformations. One where the two substituents are equatorial and one where they are axial. The conformation where they are equatorial is favored.

Yup, that sounds right.

Thanks!

No problem