Question

Identify which of the following nuclei is NMR active? 1H, 12C, 13C​

Answer 1

Answer:

NMR spectroscopy. NMR occurs due to the absorbance of radio frequency radiation to cause the "flipping" of nuclear spins from low to high energy spin states.

Explanation:

While not all nuclei are NMR active (e.g. 12C and 16O are inactive), the most important nuclei for organic chemists are 1H and 13C (both with nuclear spin = 1/2).

Answer 2

Among the following, the nuclei which are NMR active are $\[{}^1H\]$ and $\[{}^{13}C\]$.

Explanation:

• NMR spectroscopy takes place due to the absorbance of radiofrequency radiation that causes the flipping of nuclear spins from low to high energy spin states.
• The nuclei having $\[1/2\]$ integral spin are found to be NMR active.
• On the other hand, the nuclei with zero spin are observed to be NMR inactive.
• The nuclei having an odd number of protons and an odd number of neutrons have positive integer value of $I$.
• The nuclei having odd or even number of either protons or neutrons have half integral value of $I$.
• For $\[{}^1H\]$, $I=1/2$, therefore, it is NMR active.
• For $\[{}^{12}C\]$, $I=0$, so it is NMR inactive.
• For $\[{}^{13}C\]$, $I=1/2$, so it is NMR active.
• Hence, the nuclei which are NMR active are $\[{}^1H\]$ and $\[{}^{13}C\]$.

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