NMR signal enhancement in PHIP arises from the non-equilibrium populations of proton spin states in parahydrogen (pH2), i.e., dihydrogen where the protons are in a singlet spin state with vanishing total spin. The two most popular PHIP approaches today are hydrogenative PHIP and Signal Amplification by Reversible Exchange (SABRE). Hydrogenative PHIP employs a chemical transformation of a substrate molecule into a product molecule containing two protons derived from a pH2 molecule that inherit its non-equilibrium spin order . In this case, the substrate molecule has to contain a double or triple C-C bond that can undergo hydrogenation with pH2 in the presence of a specific catalyst. In SABRE, the polarization transfer from parahydrogen to the target molecule occurs through their simultaneous coordination with a suitable organometallic complex . In contrast to hydrogenative PHIP, this does not lead to chemical modification of the substrate molecule, so that the reaction process is reversible. Both these approaches have their pros and cons. In this work, we shall focus on hydrogenative PHIP and concentrate on the coherent aspects of polarization transfer between protons and heteronuclei in the product of hydrogenation, distinguishing it from SABRE where continuous chemical exchange masks coherent evolution .