Novel phenolic compounds by DFT : Electronic effects on antioxidant activity of 4‐vinylphenol derivatives

Considering the biological importance of phenolic compounds and their antioxidant activities, we have reached for 10 novel 2,6‐diX‐4‐vinylphenol derivatives (X = NMe 2 , NH 2 , OMe, Me, H, Br, Cl, F, CN, and CF 3 , 1 NMe2 ‐ 10 CF3 ), at the B3LYP/6‐311++G** level of theory. To evaluate their antioxidant efficiency, the OH bond dissociation energy (BDE) and vertical ionization potential (IP V ) are investigated for all structures in gas, water, and benzene phases, using conductor‐like polarized continuum model (CPCM) via B3LYP, LC‐ ω PBE, M05‐2X, and M06‐2X functionals. The results indicate that in going from electron‐withdrawing groups (EWGs) to electron‐donating groups (EDGs), the BDE and IP V values decrease which may suggest the increasing efficiency of antioxidants via hydrogen atom transfer (HAT) and single electron transfer (SET) mechanisms, respectively. The calculated rate constants ( k rxn ) for reactions between 1 NMe2 ‐ 10 CF3 with ·OOH and·OH radicals indicate that 1 NMe2 shows the highest one. The nucleus‐independent chemical shift (NICS) index, energies of highest occupied and lowest unoccupied molecular orbitals ( E HOMO and E LUMO , respectively), and natural bond orbital (NBO) analysis provide relevant results to understand the nature of antioxidant activity and stability of their corresponding radicals. The lowest BDE and IP V values are observed in gas and water phases, respectively. Structure 1 NMe2 turns out as the most efficient antioxidant for showing the lowest values of BDE and IP V and highest values of NICS, E HOMO , second‐order perturbation energy ( E 2 ) and natural charge. Spin densities and electrostatic potential (ESP) maps appear consistent with the obtained results. The overall order of antioxidant efficiency in gas, water, and benzene phases is 1 NMe2 > 2 NH2 >3 OMe > 4 Me > 5 H > 6 Br > 7 Cl > 8 F > 9 CN > 10 CF3 .