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Summary of the first section

1. The number of signals in the ¹H-NMR spectrum of a molecule is equal to the number of stereo-equivalent protons.
2. Protons are stereo-equivalent, if they form similar bonds, i.e., if the geometry with respect to the remainder of the molecule is identical, and if the character of the neighboring bonds is identical.
3. The identification of equivalent protons in a molecule can be achieved by two different methods. Either you can use each proton in turn as a reference point and characterize the remainder of the molecule based on it to find protons with identical environments. Or you can look for symmetry operations that relate different protons to each other.
4. In non-rigid molecules the protons of a methyl or methylene group give rise to a single, shared signal.