Subtopic: Fundamentals of Biomolecules, enzyme kinetics
Question Statement:
Which of the following spectroscopic technique(s) can be used to identify all the
functional groups of an antibiotic contaminant in food?
P. Infrared
Q. Circular dichroism
R. Nuclear magnetic resonance
S. UV-Visible
Options:
(A) P only
(B) P and R only
(C) P, Q and R only
(D) P, Q, R and S
Official Answer Key:
B
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2022 Q.45)**
**1. Governing Concept**:
- **Topic**: Biophysical & Analytical Spectroscopy (Functional Group Elucidation)
- Identifying all functional groups in an organic chemical structure:
- **P. Infrared (IR) spectroscopy**: Directly measures vibrational transition frequencies of specific covalent chemical bonds (e.g., $\text{O}-\text{H}, \text{N}-\text{H}, \text{C}=\text{O}, \text{C}-\text{O}, \text{C}\equiv\text{N}$), providing diagnostic fingerprinting of all functional groups $\rightarrow$ **ESSENTIAL**.
- **Q. Circular dichroism (CD)**: Measures differential absorption of left- and right-circularly polarized light, reporting chiral secondary/tertiary macromolecular conformation, not functional groups.
- **R. Nuclear Magnetic Resonance (NMR) spectroscopy**: $^1\text{H}$ and $^{13}\text{C}$ chemical shifts, coupling constants ($J$), and 2D correlation spectra ($\text{COSY}, \text{HSQC}, \text{HMBC}$) definitively map chemical environments and identify every functional group and molecular connectivity $\rightarrow$ **ESSENTIAL**.
- **S. UV-Visible spectroscopy**: Detects presence of conjugated $\pi$-electron systems (chromophores), but cannot differentiate individual functional groups.
- Therefore, **Infrared (P)** and **NMR (R)** are the definitive spectroscopic methods.
**2. Option Analysis**:
- **Option (A) [P only] is INCORRECT**: Incomplete; NMR is equally essential for comprehensive functional group elucidation.
- **Option (B) [P and R only] is CORRECT**: Infrared and NMR spectroscopy together identify all chemical functional groups unambiguously.
- **Option (C) is INCORRECT**: CD does not identify functional groups.
- **Option (D) is INCORRECT**: UV-Vis and CD are insufficient for functional group mapping.
**3. Final Answer**:
- **Correct Choice**: **B**
Practice This in Real CBT Exam Interface
Test yourself with the official TCS-iON palette, virtual calculator, and immediate performance analytics.