Competition between hydrogen atom transfer and carbon radical addition pathways in ClO2 oxidation of dihydroxybenzenes for water treatment: a DFT study
- 1PG & Research Department of Chemistry, Bishop Heber College (Autonomous) Affiliated to Bharathidasan University Tiruchirappalli-620017 Tamil Nadu India
Abstract
In water treatment the formation of free available chlorine (FAC) during chlorine dioxide (ClO2) oxidation influences the overall formation of chlorine-containing by-products. However, the molecular factors governing FAC formation and the role of molecular structure in determining the oxidation pathway remain poorly understood. In this study, we employed density functional theory (DFT) to investigate the ClO2-mediated oxidation of three dihydroxybenzenes, catechol (CAT), resorcinol (RES), and hydroquinone (HYQ). Two competing pathways, consecutive hydrogen atom transfer (HAT/HAT) and hydrogen atom transfer followed by carbon-radical addition (HAT/CRA), were identified for CAT and HYQ. The HAT/HAT pathway is kinetically preferred for both compounds based on the calculated activation barriers. In contrast, RES undergoes competing HAT/CRA pathways involving ortho- and para-carbon attack, followed by HOCl formation. Quantum Theory of Atoms in Molecules (QTAIM) analysis reveals that different transition-state interactions contribute to the energetics of the competing pathways. Time Dependent Density Functional Theory (TDDFT) calculations additionally show that the oxidation intermediates exhibit enhanced absorption in the UV-visible region compared with the parent dihydroxybenzenes. Overall, the results demonstrate that the hydroxyl substitution pattern influences the competition between HAT and CRA and the associated chlorine-containing products formed during ClO2 oxidation.
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BibTeX
@article{henry2026competition,
title = {{Competition between hydrogen atom transfer and carbon radical addition pathways in ClO2 oxidation of dihydroxybenzenes for water treatment: a DFT study}},
author = {Gifta Evangeline Henry and Abishek Kumaresan and Swaminathan Angeline Vedha},
journal = {RSC Advances},
year = {2026},
month = oct,
doi = {10.1039/d6ra08249a},
url = {https://doi.org/10.1039/d6ra08249a},
note = {CC BY 3.0},
}
RIS
TY - JOUR
TI - Competition between hydrogen atom transfer and carbon radical addition pathways in ClO2 oxidation of dihydroxybenzenes for water treatment: a DFT study
AU - Gifta Evangeline Henry
AU - Abishek Kumaresan
AU - Swaminathan Angeline Vedha
PY - 2026
DA - 2026/10/26
JO - RSC Advances
DO - 10.1039/d6ra08249a
UR - https://doi.org/10.1039/d6ra08249a
AB - In water treatment the formation of free available chlorine (FAC) during chlorine dioxide (ClO2) oxidation influences the overall formation of chlorine-containing by-products. However, the molecular factors governing FAC formation and the role of molecular structure in determining the oxidation pathway remain poorly understood. In this study, we employed density functional theory (DFT) to investigate the ClO2-mediated oxidation of three dihydroxybenzenes, catechol (CAT), resorcinol (RES), and hydroquinone (HYQ). Two competing pathways, consecutive hydrogen atom transfer (HAT/HAT) and hydrogen atom transfer followed by carbon-radical addition (HAT/CRA), were identified for CAT and HYQ. The HAT/HAT pathway is kinetically preferred for both compounds based on the calculated activation barriers. In contrast, RES undergoes competing HAT/CRA pathways involving ortho- and para-carbon attack, followed by HOCl formation. Quantum Theory of Atoms in Molecules (QTAIM) analysis reveals that different transition-state interactions contribute to the energetics of the competing pathways. Time Dependent Density Functional Theory (TDDFT) calculations additionally show that the oxidation intermediates exhibit enhanced absorption in the UV-visible region compared with the parent dihydroxybenzenes. Overall, the results demonstrate that the hydroxyl substitution pattern influences the competition between HAT and CRA and the associated chlorine-containing products formed during ClO2 oxidation.
SN - 2046-2069
ER -