Question:

Spin Quantum number of \( ^{13}C \) NMR is:

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- NMR-active nuclei have a nonzero spin quantum number (\( I \neq 0 \)). - \( ^{13}C \) has \( I = \frac{1}{2} \), making it ideal for NMR spectroscopy. - \( ^{12}C \) is NMR inactive because it has \( I = 0 \).
Updated On: Feb 4, 2025
  • \( \frac{1}{4} \)
  • \( \frac{1}{2} \)
  • \( \frac{3}{2} \)
  • \( \frac{1}{3} \)
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The Correct Option is B

Solution and Explanation

The spin quantum number (\( I \)) of a nucleus determines whether it is NMR active and affects its behavior in a magnetic field. The nucleus of Carbon-13 (\( ^{13}C \)) has a spin quantum number of \( \frac{1}{2} \). 

- Carbon-12 (\( ^{12}C \)) has a spin quantum number of 0 and is NMR inactive. - Carbon-13 (\( ^{13}C \)) is NMR active because it has an odd number of neutrons, resulting in a nonzero spin quantum number \( I = \frac{1}{2} \). 

- Nuclei with \( I = \frac{1}{2} \) (such as \( ^{1}H \) and \( ^{13}C \)) are the most commonly studied in NMR spectroscopy because they exhibit simple splitting patterns and good sensitivity.

 Why Other Options Are Incorrect: - (A) \( \frac{1}{4} \), (C) \( \frac{3}{2} \), (D) \( \frac{1}{3} \): These values do not correspond to the spin quantum number of \( ^{13}C \). Most nuclei with nonzero spin have values of \( I = \frac{1}{2}, 1, \frac{3}{2}, 2, \) etc., but \( ^{13}C \) specifically has \( I = \frac{1}{2} \).

 Thus, the correct answer is \( \frac{1}{2} \), confirming that \( ^{13}C \) is NMR active and useful in structural determination using \( ^{13}C \) NMR spectroscopy.

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