Most stable confirmation? [ENDORSED]

[Jamie_Cole_2N]

For a chair conformation of cyclohexane, with IUPAC name either cis- or trans- 1,4-dimethylcyclohexane, which confirmation is the most stable? And adding the methyls to two axials H's, two equatorial H's, or one axial and one equatorial would be more stable?

[Vincent Tse 2B]

The chair conformation of cyclohexane is most stable when the substituents are equatorial as this will minimize steric interactions between the "bulkiness" of the substituents and the H-atoms.

[Jamie_Cole_2N]

So, is trans- more stable in this case?

[Chem_Mod]

Yes, trans-1,4-dimethylcyclohexane is the most stable geometric isomer in the chair conformation with both methyl's in the equatorial position.
See my last lecture and page 112 in my lecture notes.

[Hyun Young Lee 2H]

is the a,a or e,e always definitely cis or is it determined by looking at the shape of the structure ?