[Babcock_Hall]

We used Hyperchem to perform molecular mechanics on trans-1,2-dimethylcyclohexane in the less stable conformation, with both groups axial.  The result the two methyl groups moved from 180° (in a constrained structure) to 160°, and the strain energy decreased.  My working hypothesis is that the reduction in 1,3-diaxial strain was greater than the increase in strain between the two methyl groups.  However, I am not sure how one would falsify or to verify this hypothesis.  One might use a tert-butyl group to lock the conformation of the cyclohexane ring with two methyl groups forced to be axial, and then one would obtain a crystal structure.  Thoughts?

[Babcock_Hall]

I suppose that another way to approach such a question is to use a higher level calculation.