Simple splitting patterns due to coupling between nuclear spins

7 Simple splitting patterns due to coupling between nuclear spins 

In dealing with chemical shifts we have assumed so far that the resonance spectrum of each nuclear spin is characterized by just one parameter, its chemical shift (or shielding constant). This is only part of the story. There are mutual interactions between nuclei with 1 0 within a molecule, and these couplings give NMR spectroscopy a unique place in the study of chemistry, in that it is often possible to count the numbers of nuclear spins present in the neighborhood of the observed one. However, it is important to note that we do not normally observe coupling between the members of a set of chemically equivalent nuclei. 

1 First-order spectra of spin-1/2 isotopes of 100% abundance 

Energy-level diagram for two spin-1/2 nuclei A and X (a) with no interaction (coupling constant 7ax = 0) and with interaction by (b) a positive and (c) a negative coupling constant. Below are the schematic spectra that would be observed. 

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