Experimental and ab Initio Studies on Solid-State Hydrogen Isotope Exchange with Spillover Tritium

Abstract

This study utilizes ab initio calculations to investigate the reaction of high-temperature solid-state catalytic isotope exchange (HSCIE) between amino acids and spillover tritium. The Hartree−Fock approximation and second-order Møller−Plesset perturbation theory in conjunction with 6-31G* and aug-cc-pVDZ basis sets were used to calculate potential energy surfaces for the interactions between CH4, alanine, hydroxyproline, and the H3O+ ion. Ab initio calculations were used to estimate the activation energies and structures of the transition states of these reactions. The hydrogen exchange reaction occurs by a synchronous mechanism, with a transition state that is characterized by pentacoordinated carbon. The proposed one-center mechanism is in good agreement with observed retention of configuration of the asymmetric carbon atoms in the HSCIE reaction with spillover tritium in experiments. The regioselectivity and stereoselectivity of hydrogen isotope exchange in amino acids with spillover tritium can be predicted on the basis of ab initio calculations of interaction of this compound with a model acidic center, taking the H3O+ ion as an example.

Tritium labeling of bioorganic compounds by isotope exchange

“…For example, the amount of tritium incorporated at 135°C into the о-position of tyrosine (relative to hydroxy group) was 20 times larger than that incorporated into the m-position, which counts in favor of the participation of tritium cations in the isotope exchange. At the same time, at 150°С the amount of tritium incorporated into the о-position of tyrosine was only 3 times larger than that incorporated into the m-position, and the molar radioactivity increased by a factor of 1.9 [34][35][36][37], i.e., the prevalence of electrophilic substitution became less pronounced.…”

Microwave‐Enhanced Radiochemistry

“…In some of these studies HTO has been replaced by T 2 as donor so that compounds of very high specific activity can be obtained. Myasoedov and colleagues [20,21] have also made extensive use of high temperature solid state catalytic isotope exchange (HSCIE) for the tritiation of a wide range of organic compounds at high specific activity.…”

Combining microwave‐enhanced deuteriation reactions with parallel synthesis procedures

“…19,20 The development of solid-state catalytic hydrogenation by Myasoedov and co-workers 21,22 has greatly increased the range of application. It is based on high temperature reactions with spillover deuterium/tritium, but the method has not been coupled to microwave irradiation.…”