I am dealing with two conformations of cis-1,4-dimethylcyclohexane. One conformation is di-axial, and the other one is di-equatorial. Why does di-axial have higher strain energy. I would make sense if the molecule was 1,3-dimethylcyclohexane because then it would the steric hinderance that would cause higher energy. Is it similar with 1,4-.. conformation? If its not steric repulsion, what factors cause di-axial to have higher strain energy?

  • $\begingroup$ Di-axial and di-equatorial in cis-1,4-dimethylcyclohexane in a chair conformation? $\endgroup$ – Klaus-Dieter Warzecha Mar 9 '15 at 9:01
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    $\begingroup$ Look at your molecule again. Are you sure you are not talking about trans-1,4-dimethylcyclohexane? In the cis-isomer both methyl groups must point in the same direction relative to the ring. That means one must be equatorial and one must be axial. $\endgroup$ – Ben Norris Mar 9 '15 at 10:44

You can't have both in a chair conformation!

  1. If the methyl groups in 1,4-dimethylcyclohexane adopt a bis-axial orientation, they are trans and they stay trans after ring flip:
    enter image description here

  2. If your 1,4-dimethylcyclohexane is cis-substituted the orientation of the methyl groups is axial and equatorial, respectively:
    enter image description here

  • $\begingroup$ They could be both equatorial in a boat or twisted configuration, though. Currently I am not too sure which is the thermodynamically most stable one. $\endgroup$ – Martin - マーチン Mar 10 '15 at 8:42

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