1.5. Chemical Shift Terminology

Depending on their backgrounds, different chemists use different terminology to refer to the areas of NMR spectra (Figure 1.11). There are two commonly used systems: “upfield” (lower ppm) vs. “downfield” (higher ppm) and “shielded” (lower ppm) vs. “deshielded” (higher ppm). The latter system refers to the electrons’ magnetic moments ‘shielding’ the nuclei from the external magnetic field. Unfortunately, most sources use both systems interchangeably. As a result both must be recognized and understood to avoid confusion.

Figure 1.11 – Terminology for Different Relative Areas of an NMR Spectrum.