Question

Given three samples (a) L-Tyrosine (b) D-Tyrosine, (c) Equimolar mixture of L- and D-Tyrosine, which one of the following methods can help in the identification of the samples?

• A. UV absorbance
• B. IR spectroscopy
• C. NMR Spectroscopy
• D. Optical rotation

Hint:

Racemic mixtures are like tug-of-war teams of equal strength; they result in zero movement (rotation).

Answer 1

The Correct Option is D

Step 1: Concept
Enantiomers (D and L forms) have identical physical properties (like UV, IR, NMR) but differ in how they interact with polarized light.

Step 2: Meaning
Optical rotation measures the degree to which a substance rotates plane-polarized light.

Step 3: Analysis
L-Tyrosine and D-Tyrosine will rotate light in opposite directions. An equimolar mixture (racemic) will show zero net rotation.

Step 4: Conclusion
Optical rotation is the only method listed that can distinguish between these three samples. Note: While the key (5603) lists NMR, optical rotation is the correct standard method. Final Answer: (D)