Polarization transfer from para-hydrogen to heteronuclei: Effect of H/D substitution. The case of AA′X and A2A2′X spin systems

Upon hydrogenation from para-hydrogen (p-H2), hyperpolarization transfer toward a heteronucleus may be possible even if the two protons are chemically equivalent in the final product (but not magnetically equivalent), provided that J couplings with the heteronucleus exist. It is however shown (theoretically and experimentally) that this transfer effectively occurs if the spin system in the hydrogenated molecule is of the type AA′X (A and A′ denoting the two protons originating from p-H2 and X the heteronucleus) but does not occur for a spin system of the A2A2′X type. A theory has been worked out for assessing the details of the X spectrum (multiplet patterns) in the case of ALTADENA and PASADENA experiments. Experimental verifications are provided.