Question

Which of the following is incorrect about a pair of enantiomers?

• A. Both enantiomers will be optically active and have equal but opposite specific rotations
• B. Each enantiomer will be non-superimposable on the other
• C. Each enantiomer will be a mirror image of the other
• D. A pair of enantiomers will behave similarly in a chiral environment

Answer 1

The correct option is D A pair of enantiomers will behave similarly in a chiral environment

Let us first look at the definition of the word enantiomers:

Enantiomers are a pair of compounds which are non-identical, non-superimposable mirror images of each other.
From Biot’s experiment, you might recall that solutions which rotated the plane polarized light are called “optically active”. Under similar conditions (of experiment), both enantiomers will rotate the plane polarized light to the same extent but in the opposite directions. As in, the specific rotation of one enantiomer will have the same magnitude as the other but with the opposite sign.

What can you say about the physical and chemical properties of a pair of enantiomers? Did you know it is very hard to separate a pair of enantiomers?
This is because, largely, the pair will have very similar physical and chemical properties. What do we mean by ‘largely’?

In achiral environments, both enantiomers behave the same way. But in chiral environments, both could have distinctly different properties. Biological systems are chiral environments which tend to have affinity for specific enantiomers. For example, L-glucose and D-glucose are a pair of enantiomers. While D-glucose is readily assimilated by higher organisms (including humans), the L-glucose enantiomer - although it has a similar sweet taste, is incompatible with the metabolic process of converting D-sugars into Pyruvate. In simple words, we cannot process the L-glucose!