Scheme 1. Schematics of Pairwise p-H2 Addition to Unsaturated Substrates.
(a) Propene, resulting in HP propane; (b) 1-butene, resulting in HP butane; (c) a mixture of trans-2-butene and cis-2-butene, resulting in HP butane. Note that here the reactions are performed under ALTADENA conditions54 and polarization redistribution55 may occur resulting in hyperpolarization of protons beyond those derived from p-H2. Note that different spin states can be overpopulated in the products of p-H2 addition to 2-butenes versus that of 1-butene, which may not be reflected in this simplified schematic. The HA and HB notations refer to the appearance of spectral lines in high-field NMR spectra.