Applications of the parahydrogen phenomenon: A chemical perspective

This review has illustrated how the field of parahydrogen assisted NMR studies has dramatically expanded since the first observations were made in 1987. Many transition metal complexes have now been observed solely because of the signal gain associate with p-H2. Furthermore, the utilisation of para-hydrogen sensitisation to probe organic derivatives will undoubtedly find more widespread use. Certainly, the fact that p-H2 is essentially unaffected by a radio-frequency pulse or a pulsed field gradient will feature in future studies because this makes it possible to remove all substrate signals without affecting the p-H2 dissolved in solution. If the two nuclei of p-H2 then move into an observable state, they give rise to the only observable NMR signals in the sample. The implications of this result are stunning: protio solvent media become NMR transparent, and reactions can be monitored for intermediates under true industrial conditions. Good hunting.