What NMR tells us
Nuclear magnetic resonance (NMR) spectroscopy is an analytical technique used to investigate organic compounds. It can provide information about the positions and chemical environments of 1H and 13C atoms within a molecule.
There are two main forms used at A-Level:
| Type of NMR | Information obtained |
|---|---|
| 1H NMR | Distinguishes different chemical environments of hydrogen atoms in an organic molecule. |
| 13C NMR | Distinguishes different chemical environments of carbon-13 atoms. Its spectra are simpler than 1H NMR spectra. |
Nuclei in different chemical environments can give signals at different positions on an NMR spectrum. These signals provide evidence about how atoms are arranged within an organic structure.
Preparing the sample
For 1H NMR, the sample is dissolved in a solvent that does not produce interfering ordinary hydrogen signals. Suitable examples include and the deuterated solvent .
- These solvents avoid unwanted 1H signals interfering with those from the sample.
- The same types of solvent can also be used for 13C NMR.
- A known solvent signal may appear in a 13C spectrum and can be identified and ignored.
NMR spectra are interpreted by comparing the positions of sample signals with a fixed reference and relating those positions to the chemical environments in the molecule.