Theoretically Estimated Experimental Adiabatic Electron Affinities of Hydrogen and Cyclohexane Molecules

Molecular hydrogen is the basis of hydrogen energy. It is formed and used in many fields of industry, physics, and chemistry. Molecular hydrogen is the main product formed during the gamma radiolysis of liquid cyclohexane. When studying the mechanism of molecular hydrogen formation during the gamma radiolysis of liquid cyclohexane, we found that the values of adiabatic electron affinity, one of the fundamental characteristics of atoms and molecules, had not yet been experimentally determined for hydrogen and cyclohexane molecules. Theoretical estimates of the adiabatic electron affinity of the hydrogen molecule made by other authors varied widely ([−0.3; −5.771] eV) and could not be compared with experimental values due to the absence of such data. Using DFT calculations at the PBE0/TZVPP level of theory, and a constructed correlation with experimental values of the adiabatic first ionization potential and electron affinity for a number of molecules, neutral radicals, and atoms, we estimated, for the first time, the experimental adiabatic electron affinities of hydrogen (−3.08 eV) and cyclohexane (−2.13 eV) molecules in the gas phase. When an electron is attached to a cyclohexane molecule, a cyclohexane radical anion is formed, a new, highly reactive species that has not been studied before. A new perspective on molecular hydrogen formation during the gamma radiolysis of liquid cyclohexane was introduced and discussed.