Question

Which one of the following is used as internal standard in NMR analysis?

• A. $Me_3SiCl$
• B. $CCl_4$
• C. $Me_4Si$
• D. $CD_3OD$

Hint:

TMS is the "Zero" of the NMR scale.

Answer 1

The Correct Option is C

Step 1: Concept NMR spectroscopy requires a reference standard to measure chemical shifts.

Step 2: Meaning The ideal standard should be chemically inert, volatile, and give a single sharp peak that doesn't overlap with most organic signals.

Step 3: Analysis Tetramethylsilane ($Me_4Si$ or TMS) has 12 equivalent protons that are highly shielded, appearing as a single peak at $0~\delta$. It is non-polar and easily removed from samples.

Step 4: Conclusion $Me_4Si$ (TMS) is the universally accepted internal standard. Final Answer: (3)