Other Homonuclear Autocorrelation Experiments

In addition to the homonuclear autocorrelated experiments just described, there are numerous additional autocorrelated experiments, the description of which is beyond the scope of this chapter. What follows is a brief, non-exhaustive listing of some of these experiments that will provide the interested reader with some entry points into the literature. 

Previous sections have exploited the scalar coupling, J, and dipolar relaxation mechanisms for purposes of autocorrelation. It is certainly possible, however, to correlate resonances via other fundamental processes. Some examples include exchange processes. As a group, these experiments are sometimes collectively referred to as EXSY (Exchange SpectroscopY) experiments [54—59]. 

Resonances can also be correlated via multiple quantum frequencies. One seminal example is found in the work of Muller [83] in which heteronuclear multiple 

Applying the idea of using multiple quantum coherence to correlate protons has also been explored. Mated and Freeman [60] reported the first experimental demonstration of proton double quantum correlated spectroscopy. The Fi axis in these experiments is used to present H chemical shift in the usual fashion. In contrast, the Fj axis is used for the double quantum frequency axis. Protons correlated to one another via double quantum coherence will exhibit a response in Fj at the algebraic sum of the offsets of the coupled resonances relative to the transmitter frequency. A scant few apphcations have been reported including an exploratory study of strychnine (2) [61] and the structural characterization of the marine natural product plumericin [62], 

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