Cyclohexan Sterics question

[meliora27]

The most stable conformation for cyclohexane is chair and I always thought that the most stable position for substituents was equatorial due to steric hinderence. I'm working on Chapter 2, Passage 1, Question 2 of Berkeley Review and there's a question about how many deuterium atoms assume axial orientation in the most stable conformation. There are 3 D's. Why would 2 be Axial and 1 Equatorial as opposed to 2 Equatorial and 1 Axial? Thanks!

 

[crazybob]

you have to calculate the total strain of one conformation, and then the total strain of the ring flip. whichever one has lower strain, is more stable.

and about the 3 deuteriums, can you draw a picture of what you see?