Proton NMR Spectroscopy

Proton nuclear magnetic resonance (Proton NMR) spectroscopy is a technique used to determine the structure of organic compounds.
This technique works by applying a magnetic field to a sample containing hydrogen atoms, which causes the atoms to align with the field.
When subjected to radio-frequency radiation, these atoms can absorb energy and ‘flip’, or resonate, and this can be recorded on a spectrum.
Each proton in a molecule will resonate at a different frequency, depending on its environment, providing unique information about the structure of the molecule.
Proton NMR spectroscopy gives two fundamental pieces of information: the chemical shift and the integration.
The chemical shift, measured in parts per million (ppm), indicates the type of environment a proton is in. More electron-rich environments cause protons to resonate at lower frequencies, resulting in a higher chemical shift.
The integration indicates the number of protons causing a particular signal. For instance, if the integration of a signal is 3, it indicates that there are three equivalent protons causing the signal.
The presence of a peak or multiple peaks at different chemical shifts can inform us about the type and number of different environments for hydrogen atoms in the molecule.
Another important aspect of a Proton NMR spectrum is splitting or multiplicity. This refers to the pattern of peaks in the spectrum and provides information about the number of protons adjacent (next to) to the proton or group of protons being considered.
Proton NMR spectroscopy is a powerful and non-destructive analytical method used to identify components of complex mixtures and to determine molecular structures of chemicals in a sample. It is a commonly used method in organic chemistry for the elucidation of structural formulae.
It is critical to understand and interpret spectra accurately as this is a key skill needed when conducting lab work and research in chemistry.
It is also important to note that NMR Spectroscopy is sensitive to the presence of impurities in the sample. It is therefore necessary to purify samples before analysis.