Comparison of Thermodynamic Energies for Elementary Steps of Anionic Hydrides to Release Hydride Ions in Acetonitrile

In this work, six thermodynamic parameters of 10 anionic hydrides XH- ascorbic acid (iAscH(-)), alcohol anions, imine anion, activated olefin anions and diene anions and their intermediates in hydride transfer process were researched. The hydride-donating, hydrogen-atom-donating and election-donating abilities of XH-, and the electron-accepting abilities of X were also discussed. Two physical parameters of free radical XH center dot, homolytic Gibbs free energy to release hydrogen atom Delta G(HD)(o)(XH center dot), heterolytic Gibbs free energy to release proton Delta G(PD)(o)(XH center dot), were determined to evaluate the antioxidant ability and acidity of intermediate XH center dot in thermodynamics. The structure-activity relationship of XH-, XH center dot and X were carefully discussed. It's easy to find that the hydride-donating abilities of XH- are stronger than their neutral compounds XH2; except for iAscH(-); the hydride-donating abilities of XH- are stronger than their hydrogen-atom-donating abilities; the hydrogen-atomdonating abilities of XH- are weaker than their intermediate radicals XH center dot; the unsaturated compounds X are easier to accept electrons than the anionic hydrides XH- to donate electrons. This paper plays an important role in determining the mechanism of anionic hydride to release hydride ion and provides a new idea for the design and synthesis of more active hydride, hydrogen and electron donors.