How does NMR use radio waves to reveal structural features of molecules?

In nuclear magnetic resonance (NMR), structural features are revealed by placing a sample in a powerful magnetic field, which causes certain atomic nuclei to align with the field and precess like spinning tops.12

When radio waves are applied to the system, these nuclei absorb energy and "flip" into a higher-energy orientation. This process is known as resonance. Because nuclei are influenced by their immediate chemical environment, those in different structural arrangements within a molecule require distinct, discrete frequencies of radio waves to flip.12

By applying a range of radio wave frequencies, chemists can correlate the specific frequencies absorbed with the structural groups and atoms present in the sample. The resulting spectrum provides detailed information about molecular structure, including the identification of chemical shifts—the separations between resonance lines caused by different electronic environments—and interactions between nuclear spins. This technique is essential for probing molecular architecture in organic chemistry and biochemistry.13