Chemistry - STEREO ISOMERISM Question with Solution | TestHub

In a chair conformation cis-1,2-dibromocyclohexane has no plane of symmetry: each chair is chiral (one Br axial, one equatorial). Ring flipping rapidly converts it into the mirror-image chair, so the two enantiomeric conformers are present in equal amounts and their rotations cancel. The sample is therefore optically inactive (it cannot be resolved), even though it is not an internal-plane meso form in any single chair. Internal compensation would need a plane in the fixed conformation, which is not the case here.

Ans. (A) Rapid interconversion of two enantiomeric conformers.