Question

Quinine and quinidine differs in:

• A. Molecular formula
• B. Rotating the plane of polarized light
• C. Chemical nature
• D. Precusors of biosynthesis

Answer 1

The Correct Option is B

Quinine and quinidine are stereoisomers, meaning they have the same molecular formula but differ in the spatial arrangement of atoms. The specific area where they differ lies in their ability to rotate the plane of polarized light.

Explanation:

• Molecular Formula: Both quinine and quinidine have the same molecular formula, which is C₂₀H₂₄N₂O₂. Hence, option "Molecular formula" is incorrect.
• Rotating the Plane of Polarized Light: Quinine is dextrorotatory whereas quinidine is levorotatory. This means quinine rotates the plane of polarized light to the right, and quinidine rotates it to the left, making this the correct difference between them. Thus, the correct answer is "Rotating the plane of polarized light".
• Chemical Nature: Both compounds are alkaloids and share similar chemical structures. Therefore, option "Chemical nature" is not the correct answer.
• Precursors of Biosynthesis: Both are biosynthetically derived from the same precursor, strictosidine, as they are stereoisomers of each other, distinguishing them by their stereochemistry rather than by different biosynthetic precursors. Thus, this option is incorrect.

In conclusion, the fundamental way in which quinine and quinidine differ lies in how they interact with polarized light. Therefore, the correct answer is "Rotating the plane of polarized light."