During the oxidation of hydrocarbons using hydrogen peroxide solutions, the evolution of gaseous oxygen is a side and undesirable process, in which the consumption of the oxidizer is not associated with the formation of target products. Therefore, no attention is paid to the systematic study of the chemical composition of the gas and the mechanisms of its formation. Filling this gap, the authors discovered a number of new, previously unidentified, interesting facts concerning both gas evolution and the oxidation of hydrocarbons. In a 33% H₂O₂/Cu₂Cl₄·2DMG/CH₃CN system, where DMG is dimethylglyoxime (Butane-2,3-dione dioxime), and is at 50 °C, evidence of significant evolution of gaseous hydrogen, along with the evolution of gaseous oxygen was found. In the authors’ opinion, which requires additional verification, the ratio of gaseous hydrogen and oxygen in the discussed catalytic system can reach up to 1:1. The conditions in which only gaseous oxygen is formed are selected. Using a number of oxidizable hydrocarbons with the first adiabatic ionization potentials (AIPs) of a wide range of values, it was found that the first stage of such a process of evolving only gaseous oxygen was the single electron transfer from hydrogen peroxide molecules to trinuclear copper clusters with the formation, respectively, of hydrogen peroxide radical cations H₂O₂^•+ and radical anions Cu₃Cl₅^•− (AIP = 5 eV). When the conditions for the implementation of such a single electron transfer mechanism are exhausted, the channel of decomposition of hydrogen peroxide molecules into gaseous hydrogen and oxygen is switched on, which is accompanied by the transition of the system to an oscillatory mode of gas evolution. In some cases, the formation of additional amounts of gaseous products is provided by the catalytically activated decomposition of water molecules into hydrogen and oxygen after the complete consumption of hydrogen peroxide molecules in the reaction of gaseous oxygen evolution. The adiabatic electron affinity of various forms of copper molecules involved in chemical processes is calculated by the density functional theory method.

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.

Molecular hydrogen, the basis of hydrogen energy, is formed in many physical and chemical processes, including the absorption of gamma-ray energy by liquid cyclohexane. From the point of view of energy consumption, the stages of gamma radiolytic formation of molecular hydrogen have not been quantified. By means of a new energy method, we analyzed the amounts of released molecular hydrogen during gamma irradiation of liquid cyclohexane in the absence and presence of small additives of bicyclic mono- and dienes RH (initial concentrations of C₀(RH) ≈ 5 × 10⁻³ M/L), depending on the first ionization potentials of the components of solutions determined in the gas phase. Using the new energy method, four primary intermediates—radical anion, electronically excited molecule, radical cation, and superexcited molecule—of liquid cyclohexane gamma radiolysis were identified. Energy, mechanistic, and spin relationships and connections between these four cyclohexane intermediates were established. The experimental value of the adiabatic electron affinity of the cyclohexane molecule is −2.01 eV. The energy of formation of the superexcited cyclohexane molecule is 18 eV (gas phase). Using the energy method, it is shown that an increase in C₀(RH) concentrations from 5 × 10⁻³ to 0.1 M/L leads to a change in the mechanism of RH consumption. Instead of RH activation, as a result of the single electron transfer reaction, RH polymerization begins, which is initiated by cyclohexyl radicals.