NMR Theories

Any successful theory must explain the observed facts. In NMR the fact is that when a sample of ethanol placed in the center of a strong magnetic field and pulsed with a narrow band of a specific radio frequency energy (rf), a spectrum of peaks will be produced. This spectrum has the following properties that must be explained:

1. only hydrogens are seen
2. there are only three peaks, presumably representing the three magnetically equivalent hydrogens in a molecule of ethanol - CH3, CH2 and OH
3. the areas under the peaks are directly proportional to the concentrations of the hydrogens in ethanol i.e. the areas are 3:2:1
4. two of the peaks are split into multiplets, while the third is a singlet
5. the intensity of the spectrum depends on the power of the rf pulse

There are two main ways to look at NMR. One way looks at the absorbance of photons by atomic nuclei. The other looks at absorption of rf energy by a sample.

List of topics in this section

• Micro level - at the level of the nucleus

• Macro level - at the level of the sample

• NMR of solids - it is still fundamentally NMR, but the technical challenges of having a solid vs a liquid need a whole section to describe the theory