Question

\( ^1H \) NMR spectra recorded in CDCI\(_3\) solution typically show a resonance at 7.24 ppm. What is this resonance due to?

• A. \( \text{water} \)
• B. \( \text{trace HC} \)
• C. \( \text{Chloroform} \)
• D. \( \text{exchangeable protons} \)

Hint:

Deuterated solvents are used in NMR spectroscopy to minimize interference with sample signals while providing useful reference peaks.

Answer 1

The Correct Option is D

The resonance at 7.24 ppm in \( ^1H \) NMR spectra of CDCI\(_3\) is due to residual chloroform (\( \text{CHCl}_3 \)). Chloroform-d (\( \text{CDCl}_3 \)) is commonly used as an NMR solvent, and residual protonated chloroform leads to this characteristic peak. This peak serves as a useful reference for chemical shift calibration.