Chair conformation stability - 1,3-diaxial Interactions

One way to think of this problem is in terms of cis or trans. 1,3 or 1,5 axial side groups are in cis with each other, they are on the same side of the ring which causes steric strain. 1,2 equatorial r-groups are in trans with one another, pointing towards opposite sides of the ring (one points downward and the other points upward). This alone extremely diminishes the steric strain . Also, 1 axial and 2 equatorial are in cis confirmation with each other and that would be less stable than 1,2 equatorial groups. However, from the imagine provided it would appear that 1 axial and 2 equatorial molecules would be further apart from each other than 1,2 equatorial groups -- which isn't the case and thus the image can be a bit misleading.

Your proposed question is difficult though because the idea of having less hindrance on adjacent trans molecules than separated 1,3 cis molecules isn't always that intuitive.

I haven't worked o-chem problems in 6 months, but that is my reasoning behind things.

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Chair conformation stability - 1,3-diaxial Interactions