Effect of Temperature during Preactivation of 5% Pd/C and 5% Pd/Al2O3 with Deuterium Gas on the Isotope Exchange between Deuterium Water and an Organic Compound

As demonstrated by the example of serotonin, 3-(N-pyrrolyl)propanoyl-L-histidine, sodium p-phenylbenzoate, and Pro–Gly–Pro, activation of the isotope exchange with D₂O also occurred when a solution of an organic compound in D₂O was mixed with 5% Pd/Al₂O₃ or 5% Pd/С (after preliminary treatment of catalysts with deuterium gas on heating). When implementing this technique, 2–3 atoms of deuterium were incorporated in serotonin, 4–5 atoms, in Pro–Gly–Pro, 7–8 atoms, in 3-(N-pyrrolyl)propanoyl-L-histidine, and 3–4 atoms, in sodium p-phenylbenzoate. In the latter case, as judged from the composition of the reaction products, atomic deuterium takes part in the activation of isotope exchange with D₂O. The participation of atomic deuterium in these reactions follows from the intensification of the degradation of the compounds during deuteration. When using compounds that do not contain labile fragments, isotope exchange with D₂O can be activated by keeping the catalyst at room temperature and heating.