When a nucleus moves between two (sometimes more) chemical states we have Dynamic NMR. Common examples are: the equilibrium between conformers; complexes that can have two different structures, etc. "Chemical Exchange" is the expression that encompasses everything. The principle is so general, that the kind of chemical bonds that are created and destroyed is not relevant. What matters is the rate of exchange between the two states. If the exchange is slow, you see nothing in 1-D, but you see a cross-peak in the EXSY spectrum (another name for the more familiar NOESY). If the exchange is a little faster, you see two broad signals in 1-D. Warm the sample and the exchange becomes faster and faster: you see a single signal, but quite a broad one. At higher rates the single signal is so sharp that we don't mention Dynamic NMR anymore. More exactly, the appearance of the spectrum depends both on the rate of exchange and on the difference (in Hz) between the two peaks. If we in...
