Question

If there is no rotation of plane polarised light by a compound in a specific solvent, though it is chiral, it may mean that

• A. the compound is certainly meso
• B. there is no compound in the solvent
• C. the compound may be a racemic mixture
• D. the compound is certainly a chiral

Answer 1

Answer: (A)

Meso compound does not rotate plane polarised light. Compound which contains tetrahedral atoms with four different groups but the whole molecule is achiral, is known as meso compound. It possesses a plane of symmetry and is optical inactive. One of the asymmetric carbon atoms turns the plane of polarised light to the right and other to the left and to the same extent so that the rotation due to upper half is compensated by the lower half, i.e., internally compensated, and finally there is no rotation of plane polarised light.