[amp_mcq option1=”a, a” option2=”e, e” option3=”a, e” option4=”pseudo-a, pseudo-e” correct=”option3″]
The correct answer is C. a, e.
In cis-decalin, the two methyl groups are on the same side of the ring. This makes the molecule very strained, and it exists in a conformation where the two methyl groups are as far apart as possible. In this conformation, the bridge-head hydrogen is in an axial position on one ring and an equatorial position on the other ring.
Option A is incorrect because both bridge-head hydrogens would be in axial positions. This would make the molecule even more strained, and it is not a stable conformation.
Option B is incorrect because both bridge-head hydrogens would be in equatorial positions. This would make the molecule less strained, but it is still not a stable conformation.
Option D is incorrect because the bridge-head hydrogens are not in pseudo-axial or pseudo-equatorial positions. These are special positions that are not axial or equatorial, but are in between. They are not stable positions for the bridge-head hydrogens in cis-decalin.