Question

\( ^{13}C \) chemical shift has a much wider range (<300 ppm) than \( ^1H \) (<10 ppm) because:

• A. The contribution of the diamagnetic shielding of \( ^{13}C \) is much larger than \( ^1H \) due to the small \( ^{13}C \) energy.
• B. The contribution of the paramagnetic shielding of \( ^{13}C \) is much larger than \( ^1H \) due to the small \( ^{13}C \) energy.
• C. The electron density of \( ^1H \) is usually spherically symmetrical.
• D. The reason is unknown.

Hint:

\( ^{13}C \) chemical shifts provide essential information about molecular structure due to the broad range of shielding effects.

Answer 1

The Correct Option is B

\( ^{13}C \) nuclei exhibit a wider chemical shift range due to greater paramagnetic shielding effects compared to \( ^1H \). This occurs because carbon atoms are influenced by both diamagnetic and paramagnetic contributions, whereas hydrogen nuclei are largely diamagnetically shielded. These differences allow \( ^{13}C \) NMR spectroscopy to provide more detailed insights into molecular structure.