It is recommended to put between 10 and 15 mg of sample in 0.66 mL of deuterated solvent to put the sample inside the NMR tubes.

In order to request the analysis of a sample by NMR, you must contact the staff responsible for the equipment.

You will need to give the toxicity and any storage precautions. Once the report has been delivered, if you do not collect the sample within one week, any remaining sample will be destroyed.

The physical basis of NMR spectroscopy lies in the magnetic properties of the atomic nucleus.The interaction of the magnetic moment of a nucleus with an external magnetic field causes a splitting of the energy levels.Transitions between these different states can be generated and the energy absorption can be detected and recorded as a spectral line, called a resonance signal.In this way, spectra can be obtained for compounds containing atoms whose nuclei have non-zero magnetic moments.Among these are the ¹H, ¹⁹F, ¹⁴N and ¹⁵N and others of interest in chemistry.The ¹²C nucleus, of great importance in organic chemistry, has an even atomic mass and atomic number, and therefore no magnetic moment.Thus, C NMR studies are limited to the ¹³C isotope, which has a natural abundance of only 1.1%.

From an NMR spectrum we can extract three basic pieces of information that we need to be able to determine the structure in solution of our molecule:

1. The position of the signal (chemical shift, δ).Different resonance signals appear for the different protons in the molecule because these protons have different chemical environments.
2. Not all lines are simple (singlets) but some are split into doublets, triples, quadruplets or other multiplicities.This splitting is due to spin-spin coupling.And it gives us an idea about the coupling system.
   
3. The area under a signal is related to the number of ¹Hs that give rise to the signal and can be measured by integration.It should also be taken into account that spectra can be made of other nuclei, such as ¹³C, ³¹P, ¹⁵N, etc.,and apply two-dimensional correlation techniques, special techniques that allow spectra to be recorded in two independent frequency dimensions.In many experiments one frequency axis contains chemical shifts and the other, coupling constants.
   

They can also contain frequencies of a single nucleus (homonuclear) or of different nuclei (heteronuclear).This type of experiment is important for the analysis of complex spectra with a large overlap of signals and allows the study of systems as complex as natural products, biopolymers, proteins or nucleic acids.

1.Determination of structures

Correlations between chemical shift or spin-spin coupling and the structure of compounds form the basis of the application of NMR to the determination of structures of unknown compounds.Thus, the chemical shift makes it possible to know the chemical environment in which a nucleus is located and the integration allows conclusions to be drawn regarding the number of nuclei present.Spin-spin coupling allows us to define the relative positions of the nuclei, since the magnitude of the spin-spin interaction (coupling constant, J) depends on the number and type of bonds separating the different nuclei.

2.Study of dynamic processes.Study of fast reversible reactions

Another application of NMR spectroscopy derives from the observation that the NMR spectrum of many compounds depends on temperature.That is, the shape of the NMR signal depends on dynamic processes and the rate at which these processes take place.Therefore, the spectroscopy of NMR can be used for the study of fast reversible reactions that cannot be followed with the classical kinetic methods.

3.Study of reaction mechanisms

In addition, NMR spectroscopy is also useful for the study of reaction mechanisms in all branches of chemistry.These experiments use isotopes of hydrogen, carbon or nitrogen (²H, ¹³C, ¹⁵N) to track a particular atom during the reaction of interest.

4.Interest in other scientific areas

In organic chemistry and biochemistry, ¹³C NMR spectroscopy plays a fundamental role, although ¹⁹F, ¹⁵N i ³¹P also provide valuable information.In inorganic chemistry, a large number of nuclei of interest can be used thanks to the rapid development of experimental techniques.Since almost every element in the periodic table contains a stable isotope with a magnetic moment, the area of application of NMR spectroscopy is very wide, even though the natural abundance of many of these isotopes is small.

• Specialisd Nuclear Magnetic Resonance Group (Royal Spanish Society of Chemistry)