Chemical Shifts

The chemical shift describes the resonant frequency of a nucleus compared to a standard in a magnetic field. The resonant frequency depends on the nucleus' local environment such as binding partners and geometry.

Figure 1 shows the range for carbon-13 NMR.

Chemical shift range for carbon NMR. Aliphatic carbons range 10 to 40 ppm, alcohols and amines - 30 to 110 ppm, electronegative groups 60 to 100 ppm, aromatic carbons 115 to 155 ppm, alkenes 100 to 150, alkynes 100 to 130 ppm, Carboxylic acid chemical shift range - 170 to 205 ppm, ester 155 to 190 ppm, ketone 200 to 215 and aldehydes 200 to 230 ppm

Figure 1: Functional Group chemical shift ranges for carbon-13 NMR

The range is 20 times the chemical shift range for proton NMR.