Hydrogen induced polarization-nuclear-spin hyperpolarization in catalytic hydrogenations without the enrichment of para- or orthohydrogen

During the last 40 years, Prof. Dr. Joachim Bargon, to whom several articles in this issue are dedicated, has contributed more than 90 scientific publications to the understanding of NMR hyperpolarization phenomena such as chemically induced dynamic nuclear polarization (CIDNP) or parahydrogen induced polarization (PHIP). Both techniques are extremely useful for elucidating the mechanisms and kinetics of chemical reactions involving radicals or catalytic hydrogenations, respectively. To honor Joachim Bargon's scientific achievements, we dedicate to him an additional, newly discovered and somewhat unexpected twist to the PHIP methodology. Accordingly, NMR spectra exhibit the unique, enhanced absorption and emission patterns of PHIP not only if the hydrogen for the catalytic reactions is enriched in one of its nuclear spin states (parahydrogen or orthohydrogen) but also if it is at its thermodynamic equilibrium. Thermally equilibrated gaseous hydrogen is obtained from commercially available hydrogen gas bombs or from electrolytic hydrogen generators. The new finding is explained with the quantum mechanical properties of the small, highly symmetric hydrogen molecule.