Question: Which of the following is 'not' true about enantiomers?

Step 1 (Governing Principle & Definition): [0.5 Mark]

Enantiomers are stereoisomers that are non-superimposable mirror images of each other. According to the NCERT Chemistry textbook (Haloalkanes and Haloarenes chapter), enantiomers possess identical physical properties (such as melting point, boiling point, refractive index, and solubility) in an achiral environment. However, they differ in their interaction with plane-polarized light and their reactivity in chiral environments.

Step 2 (Step-by-Step Analysis of Options): [0.25 Mark]

• (A) Chemical reactivity: Enantiomers have identical chemical reactivity toward achiral reagents.
• (B) Specific rotation: Enantiomers rotate the plane of plane-polarized light to the same extent but in opposite directions ($+\alpha$ and $-\alpha$). Therefore, they do not have the same specific rotation.
• (C) Melting/Boiling point: These are physical properties and are identical for enantiomers.
• (D) Refractive index: This is a physical property and is identical for enantiomers.

Step 3 (Final Concluded Answer): [0.25 Mark]

The statement that is not true is (B). While the magnitude of specific rotation is the same, the direction is opposite, making the specific rotation values distinct (e.g., $+x^\circ$ vs $-x^\circ$).

💡 EL10 Concept Insight: Think of enantiomers like your left and right hands; they look identical in a mirror and weigh the same, but they are fundamentally different because you can't perfectly overlap them. Because they are "opposites," they twist light in opposite directions, even though all their other physical measurements remain exactly the same.