Carbon NMR Spectra

Applications of ¹³C NMR -- The most abundant isotope ¹²C has no overall nuclear spin, having an equal number of protons and neutrons. The ¹³C isotope however does has spin 1/2, but is only 1% abundant.  They are characterized by the following:

• A chemical shift range of about 220 ppm, normally expressed relative to the ¹³C resonance of TMS.
• A natural line width of about 1 Hz, related to the values of the relaxation times T₁ and T₂.
• A Larmor frequency in the range of 20-100 MHz, for typical spectrometers.
• Typically about 5-20 mg of sample dissolved in 0.4 - 2 mL of solvent (normally CDCl₃) are required, and a good spectrum would be obtained in 64 - 6400 scans.