[ramboacid]

I know that substituents on a cyclohexane ring orient themselves (axial/equatorial) to minimize repulsions, but all the examples I've seen so far leave the cyclohexane ring in the chair conformation. Are there any situations where the substituents, in minimizing their repulsions, change the conformation of cyclohexane from the chair conformation to another conformation, like envelope, boat, or twist-boat? I'd imagine the substituents have to be pretty bulky, but none of the examples I've seen with even t-butyl groups change the conformation...

[spirochete]

Yes there is a 1,4 isomer of cyclohexane with t-butyls that favors the twist boat (not the straight boat, that's a transition state). It's the diastereomer that is forced to put one t-butyl axial no matter the chair conformation.

[ramboacid]

Could intramolecular hydrogen bonding energetically compensate for steric repulsion in the less ideal conformations? I've seen it in chair conformations, but could it stabilize a 1,4 diol cyclohexane in the boat conformation? (Or other cyclohexane derivatives)

[C-hemCards]

Good question, but no on the diol. There are more interactions in a boat than just at the 1 and 4 positions. Also, hydrogen bonds operate at optimal distances and have defined energetic benefits (that can be calculated). Additionally, the hydrogen bonding would be highly solvent dependent.

There are many relatively simple systems out there that are stable in boats or twist-boats.