Carbon-13 NMR (
<sup>13</sup>C 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 <sup>13</sup>C NMR is an important tool in
chemical structure elucidation in
organic chemistry. <sup>13</sup>C 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
<sup>13</sup>C NMR has a number of complications that are not encountered in proton NMR. <sup>13</sup>C NMR is much less sensitive to carbon than <sup>1</sup>H NMR is to hydrogen since the major isotope of carbon, the <sup>12</sup>C 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 <sup>13</sup>C isotope, present naturally at 1.1% natural abundance, is magnetically active with a spin quantum number of 1/2 (like <sup>1</sup>H) and therefore detectable by NMR. Therefore, only the few <sup>13</sup>C 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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