article · Heliyon
Computational chemical investigations using density functional theory examine how 1,3,4-oxadiazole derivatives neutralise oxygen-centred free radicals in both gas phase and water. The analysis evaluates three distinct radical scavenging mechanisms: hydrogen atom transfer, single electron transfer followed by proton transfer, and sequential proton loss electron transfer. Key thermodynamic indicators, including bond dissociation enthalpy, adiabatic ionisation potential, proton dissociation enthalpy, proton affinity, and electron transfer enthalpy, characterise each pathway. Molecular orbital predictions for electron donation correlate well with electron transfer enthalpy values at preferred reactive sites. Calculations of Gibbs free energy indicate that these molecules scavenge peroxyl radicals most efficiently through hydrogen atom transfer and sequential proton loss electron transfer in a vacuum. However, in an aqueous environment, single electron transfer followed by proton transfer emerges as the dominant reaction pathway.
Free radicals can cause cellular damage and degrade materials, making antioxidant molecules essential in medicine and industrial chemistry. Understanding the exact chemical mechanisms through which compounds like 1,3,4-oxadiazole neutralise radicals in different environments helps researchers predict antioxidant performance and guide the design of more effective protective chemical agents.
This fundamental computational research sits at an early stage. While understanding how 1,3,4-oxadiazole derivatives neutralise free radicals could inform future antioxidant formulation in pharmaceuticals or materials science, the abstract provides purely theoretical thermodynamic data and does not indicate a direct commercial application pathway or product development plan.
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The thermodynamics of free radical scavenge of 1,3,4-oxadiazole derivatives towards oxygen-centred free radicals were investigated by the density functional theory (DFT) method in the gas phase and aqueous solution. Three mechanisms of free radical scavenge namely, hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET) were considered. The antioxidant descriptors that characterize these mechanisms such as, bond dissociation enthalpy (BDE), adiabatic ionization potential (AIP), proton dissociation enthalpy (PDE), proton affinity (PA) and electron transfer enthalpy (ETE) were evaluated. The sequence of electron donation as predicted by the HOMO results were in good agreement with the sequence of ETE for the considered molecules at their favoured sites of free radical scavenge. The reaction Gibbs free energy for inactivation of the selected peroxyl radicals, show that 1,3,4-oxadiazole antioxidants are more efficient radical scavengers by HAT and SPLET mechanisms than SET-PT mechanism in vacuum. In aqueous solution, the SET-PT mechanism was observed to be the dominant reaction pathway.
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DOI: 10.1016/j.heliyon.2020.e03683
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