There are three important parts in the interpretation of a 1H NMR spectrum.
Before attempting to determine the structure of any molecule you should consider the integration, multiplicity, and chemical shift of each individual resonance within a spectrum. Subsequent to gathering all this information it is recommended that you determine each part of the molecule represented by each resonance and put it together as shown in the movie clip shown below (or at http://screencast-o-matic.com/watch/coiQ2MfT25) .
Suggested Steps for NMR interpretation:
1. Determine Degree of Unsaturation if molecular formula is provided.
2. Use other information provided (IR, Mass Spec, etc.) to determine any obvious functional groups
3. Label individual signals and make a table to help organize your thoughts.
4. Consider the integration of each resonance. You will need to determine whole number ratios from the given integral values.
5. Consider the multiplicity of each signal to determine the number of protons on neighboring carbon atoms.
6. Consider the chemical shift of each signal. This will help you determine the location of each group with regards to any functional groups present.
7. Identify possible fragments. [Writing each fragment on small pieces of paper or post-it notes will allow you to move each fragment easily to determine its appropriate location within the molecule.]
8. Assemble fragments. [This may require multiple rearrangements before the molecule formed is chemically sound and consistent with the NMR data provided.]
9. Draw the molecule and check
10. Label all peaks including the standard (typically TMS) and residual solvent peak(s). Any impurities should be labeled as well.
NMR is rarely used without the aid of other information. You may be given other types of spectra to help you glean the necessary information or you may be given the information outright.
Here are some other types of spectra often used to help determine the structure of the molecule analyzed with 1H-NMR spectroscopy:
Mass Spectrum – molecular weight
IR (infra-red) spectrum – important functional groups within the molecule
13C NMR spectrum – number of unique carbon atoms