Scholarlink

<p>The antioxidant activity of phenolic compounds is closely related to their ability to donate a hydrogen atom from the hydroxyl (O–H) group, which is largely determined by the O–H bond dissociation energy (BDE). In this work, a systematic density functional theory (DFT) investigation was conducted to evaluate the influence of substituent type and positional arrangement on the antioxidant properties of phenol derivatives. A series of substituted phenols bearing methyl (–CH<sub>3</sub>), amino (–NH<sub>2</sub>), methoxy (–OCH<sub>3</sub>), and mercapto (–SH) groups at ortho-, para-, di-, and tri-substituted positions were examined. All molecular geometries were optimized, and thermochemical calculations were performed to determine O–H BDE values in gas phase and several subsets were computed in polar media (water and methanol). To elucidate the electronic factors governing radical stabilization, frontier molecular orbital (FMO) analysis, spin density distribution, molecular electrostatic potential (MEP) mapping, and natural bond orbital (NBO), density of states (DOS) analysis were carried out. The results reveal that electron-donating substituents significantly reduce O–H BDE by increasing electron density and enhancing resonance stabilization of the phenoxyl radical. Aminophenol derivatives exhibit the lowest BDE values due to the strong resonance-donating ability of the –NH<sub>2</sub> group, whereas methyl- and mercapto-substituted systems show comparatively weaker effects. Furthermore, para- and polysubstitution enhances radical stabilization through extended π-conjugation and improved spin density delocalization. These findings provide detailed electronic insights into substituent-dependent antioxidant activity and offer theoretical guidance for the rational design of efficient phenolic antioxidants.</p>

错误：搜索内容不能为空，请输入英文关键词
错误：关键词超出字数限制，请精简
高级检索

Computational study of the effects of substituent type and position on the O–H bond dissociation energy of phenolic compounds

  • 期刊论文

  • 出版模式：

    开放获取

  • 发表日期：

    2026年7月14日

查看全文
  • Jewel Hossen,
  • Md. Forhad Babu,
  • Tanu Dey,
  • Shahriar Siam,
  • Md. Mazharul Islam,
  • Md. Masum Iqbal,
  • Apel Mahamud Rabby,
  • Md. Tanvir Rashid Rezvi

摘要

The antioxidant activity of phenolic compounds is closely related to their ability to donate a hydrogen atom from the hydroxyl (O–H) group, which is largely determined by the O–H bond dissociation energy (BDE). In this work, a systematic density functional theory (DFT) investigation was conducted to evaluate the influence of substituent type and positional arrangement on the antioxidant properties of phenol derivatives. A series of substituted phenols bearing methyl (–CH3), amino (–NH2), methoxy (–OCH3), and mercapto (–SH) groups at ortho-, para-, di-, and tri-substituted positions were examined. All molecular geometries were optimized, and thermochemical calculations were performed to determine O–H BDE values in gas phase and several subsets were computed in polar media (water and methanol). To elucidate the electronic factors governing radical stabilization, frontier molecular orbital (FMO) analysis, spin density distribution, molecular electrostatic potential (MEP) mapping, and natural bond orbital (NBO), density of states (DOS) analysis were carried out. The results reveal that electron-donating substituents significantly reduce O–H BDE by increasing electron density and enhancing resonance stabilization of the phenoxyl radical. Aminophenol derivatives exhibit the lowest BDE values due to the strong resonance-donating ability of the –NH2 group, whereas methyl- and mercapto-substituted systems show comparatively weaker effects. Furthermore, para- and polysubstitution enhances radical stabilization through extended π-conjugation and improved spin density delocalization. These findings provide detailed electronic insights into substituent-dependent antioxidant activity and offer theoretical guidance for the rational design of efficient phenolic antioxidants.