Carbon-13 NMR

Carbon-13 NMR (¹³C NMR or sometimes simply referred to as carbon NMR) is the application of nuclear magnetic resonance spectroscopy to carbon. It is analogous to proton NMR ( NMR) and allows the identification of carbon atoms in an organic molecule just as proton NMR identifies hydrogen atoms. As such ¹³C NMR is an important tool in chemical structure elucidation in organic chemistry. ¹³C NMR detects only the isotope of carbon, whose natural abundance is only 1.1%, because the main carbon isotope, , is not detectable by NMR since it has zero net spin.

Implementation

¹³C NMR has a number of complications that are not encountered in proton NMR. ¹³C NMR is much less sensitive to carbon than ¹H NMR is to hydrogen since the major isotope of carbon, the ¹²C isotope, has a spin quantum number of zero and so is not magnetically active and therefore not detectable by NMR. Only the much less common ¹³C isotope, present naturally at 1.1% natural abundance, is magnetically active with a spin quantum number of 1/2 (like ¹H) and therefore detectable by NMR. Therefore, only the few ¹³C nuclei present resonate in the magnetic field, although this can be overcome by isotopic enrichment of e.g. protein samples. In addition, the gyromagnetic ratio...
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