Question

A pair of enantiomers will have the same

• A. melting point
• B. effect on plane polarized light
• C. refractive index
• D. smell

Answer 1

Answer: (A), (C)

refractive index

For most part, either of the compounds in a pair of enantiomers will have the same physical and chemical properties. So, properties which do not depend on any interaction with a chiral substance or environment will be identical for both enantiomers. So definitely, melting and boiling points, and refractive indices will all have the same value.

Do not confuse refractive index with optical activity. Optical activity refers to the effect that these compounds have on a plane polarized light - they rotate the plane of the polarized light. Refractive index is a measure of how light propagates in a medium as compared to vacuum.

So a pair of enantiomers will not have the same effect on a plane polarized light. They will rotate the planes in the opposite directions! What can you say about smell? Certainly, it is a sense associated with a biological system – a chiral environment. So smells will likely be different for different enantiomers. Let us put it this way – two will not always smell alike.