The Modern Chemistry Lab

Spectroscopy and Spectrometry

How does NMR help chemists determine the structure of a compound?

The peaks in an NMR spectrum can be related to certain properties of a molecule’s structure. The number of peaks present tells how many types of chemically distinct atoms of a given element are present. A single NMR spectrum typically only contains information about a single element (for organic molecules, hydrogen or carbon NMR spectra are the most common), so it can be useful to record multiple NMR spectra for the same compound. The location of the peaks along the x-axis is known as the chemical shift, and this value can be related to the electron density surrounding each nucleus. In some NMR spectra, the intensities of each peak (their height on the y-axis) can be related to the number of nuclei of a given element that are present. There are more and more details that one learns after spending lots of time interpreting NMR spectra, but these are the basic principles that allow a chemist to relate an NMR spectrum to a chemical structure.


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