Carbon-13 NMR

Carbon-13 nuclear magnetic resonance (most commonly known as carbon-13 NMR or ¹³C NMR or sometimes simply referred to as carbon NMR) is the application of nuclear magnetic resonance (NMR) spectroscopy to carbon. It is analogous to proton NMR (1
H
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 13
C
isotope of carbon, whose natural abundance is only 1.1%, because the main carbon isotope, 12
C
, is not detectable by NMR since it has zero net spin.

¹³C chemical shifts follow the same principles as those of ¹H, although the typical range of chemical shifts is much larger than for ¹H (by a factor of about 20). The chemical shift reference standard for ¹³C is the carbons in tetramethylsilane (TMS), whose chemical shift is considered to be 0.0 ppm.

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