Question

Which among the following is NOT a true statement for enantiomers?

• A. Enantiomers have identical refractive index.
• B. Enantiomers are superimposable mirror images of each other.
• C. Enantiomers have same chemical properties.
• D. Enantiomers have equal but opposite optical rotation.

Hint:

Chemistry Tip: The term "chiral" comes from the Greek word for "hand". Always use the left/right hand analogy to remember that while they are perfect mirror reflections, they are absolutely non-superimposable.

Answer 1

The Correct Option is B

Concept: Chemistry (Organic Chemistry) - Stereochemistry and Properties of Enantiomers.

Step 1: Define the fundamental nature of enantiomers. Enantiomers are a specific type of stereoisomers. By definition, they are chiral molecules that are exact mirror images of one another but cannot be perfectly aligned or placed on top of each other.

Step 2: Evaluate Option A (Physical properties). Because enantiomers have the exact same types of atoms and bonds in the same connectivity, they exhibit identical physical properties in an achiral environment. This includes melting points, boiling points, densities, and refractive indices. Therefore, statement (A) is true.

Step 3: Evaluate Option C (Chemical properties). Enantiomers react identically when placed in an achiral chemical environment or when reacting with achiral reagents. Their chemical properties only differ when interacting with other chiral substances (like enzymes). In a general context, statement (C) is considered true.

Step 4: Evaluate Option D (Optical rotation). The primary physical distinction between two enantiomers is their interaction with plane-polarized light. While they rotate the light by the exact same magnitude (equal angle), they rotate it in opposite directions (one dextrorotatory, one levorotatory). Therefore, statement (D) is true.

Step 5: Evaluate Option B (Superimposability) and conclude. The defining characteristic of chirality is the lack of superimposability.
Just like a person's left hand and right hand are mirror images but cannot be perfectly overlapped palm-to-palm and thumb-to-thumb facing the same direction, enantiomers are strictly non-superimposable.
Therefore, the statement "Enantiomers are superimposable mirror images of each other" fundamentally contradicts the core definition of an enantiomer. This makes Option (B) the only false statement in the list. $$ \therefore \text{Option B is NOT a true statement for enantiomers.} $$