Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents
The electrochemical behavior of selected phenolic benzotriazoles (BZTs), namely 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐bis(1‐methyl‐1‐phenylethyl)phenol and 2,4‐di‐tert‐butyl‐6‐(5‐chlorobenzotriazol‐2‐yl)phenol (commercial names UV234 and UV327, respectively) were examined with cyclic voltammetry (CV) and con...
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| Format: | Journal Article |
| Language: | English |
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2020
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| Online Access: | https://hdl.handle.net/10356/139621 |
| _version_ | 1826111220775649280 |
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| author | Chan, Ya Yun Webster, Richard David |
| author2 | School of Physical and Mathematical Sciences |
| author_facet | School of Physical and Mathematical Sciences Chan, Ya Yun Webster, Richard David |
| author_sort | Chan, Ya Yun |
| collection | NTU |
| description | The electrochemical behavior of selected phenolic benzotriazoles (BZTs), namely 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐bis(1‐methyl‐1‐phenylethyl)phenol and 2,4‐di‐tert‐butyl‐6‐(5‐chlorobenzotriazol‐2‐yl)phenol (commercial names UV234 and UV327, respectively) were examined with cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in acetonitrile and dichloromethane solutions. CV indicated that both phenolic BZTs undergo a chemically irreversible oxidation process at approximately Ep°x=+1.0 V vs. Fc/Fc+ (where Ep°x is the anodic peak potential and Fc=ferrocene) to form compounds that cannot be electrochemically converted back to the starting material on the voltammetric timescale. In basic conditions, cyclic voltammetry experiments indicated that the corresponding phenolates (prepared by reacting the phenols with equiv. mols of n‐Bu4NOH) were oxidized at Ep°x∼−0.2 V vs. Fc/Fc+ via a one‐electron diffusion controlled process with anodic (ip°x) to cathodic (ipred) peak current ratios (ip°x/ipred)≫1, suggesting that the produced phenoxyl radicals decomposed rapidly via a chemical step. However, electron paramagnetic resonance (EPR) experiments performed on the bulk electrolyzed solutions of the phenolates after one‐electron bulk oxidation indicated long lifetimes of the UV234. and UV327. phenoxyl radicals. Therefore, the long timescale CPE and spectroscopic (UV‐vis and EPR) studies provided good evidence of a reversible dimerization mechanism between the phenoxyl radicals, which explained the apparent discrepancy with the short timescale CV experiments. |
| first_indexed | 2024-10-01T02:47:07Z |
| format | Journal Article |
| id | ntu-10356/139621 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T02:47:07Z |
| publishDate | 2020 |
| record_format | dspace |
| spelling | ntu-10356/1396212020-05-20T08:37:17Z Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents Chan, Ya Yun Webster, Richard David School of Physical and Mathematical Sciences Nanyang Environment and Water Research Institute Science::Chemistry Electrochemical Oxidation Phenolic Benzotriazoles The electrochemical behavior of selected phenolic benzotriazoles (BZTs), namely 2‐(2H‐benzotriazol‐2‐yl)‐4,6‐bis(1‐methyl‐1‐phenylethyl)phenol and 2,4‐di‐tert‐butyl‐6‐(5‐chlorobenzotriazol‐2‐yl)phenol (commercial names UV234 and UV327, respectively) were examined with cyclic voltammetry (CV) and controlled potential electrolysis (CPE) in acetonitrile and dichloromethane solutions. CV indicated that both phenolic BZTs undergo a chemically irreversible oxidation process at approximately Ep°x=+1.0 V vs. Fc/Fc+ (where Ep°x is the anodic peak potential and Fc=ferrocene) to form compounds that cannot be electrochemically converted back to the starting material on the voltammetric timescale. In basic conditions, cyclic voltammetry experiments indicated that the corresponding phenolates (prepared by reacting the phenols with equiv. mols of n‐Bu4NOH) were oxidized at Ep°x∼−0.2 V vs. Fc/Fc+ via a one‐electron diffusion controlled process with anodic (ip°x) to cathodic (ipred) peak current ratios (ip°x/ipred)≫1, suggesting that the produced phenoxyl radicals decomposed rapidly via a chemical step. However, electron paramagnetic resonance (EPR) experiments performed on the bulk electrolyzed solutions of the phenolates after one‐electron bulk oxidation indicated long lifetimes of the UV234. and UV327. phenoxyl radicals. Therefore, the long timescale CPE and spectroscopic (UV‐vis and EPR) studies provided good evidence of a reversible dimerization mechanism between the phenoxyl radicals, which explained the apparent discrepancy with the short timescale CV experiments. MOE (Min. of Education, S’pore) 2020-05-20T08:37:17Z 2020-05-20T08:37:17Z 2018 Journal Article Chan, Y. Y., & Webster, R. D. (2019). Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents. ChemElectroChem, 6(16), 4297-4306. doi:10.1002/celc.201801375 2196-0216 https://hdl.handle.net/10356/139621 10.1002/celc.201801375 2-s2.0-85056872695 16 6 4297 4306 en ChemElectroChem © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. All rights reserved. |
| spellingShingle | Science::Chemistry Electrochemical Oxidation Phenolic Benzotriazoles Chan, Ya Yun Webster, Richard David Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title | Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title_full | Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title_fullStr | Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title_full_unstemmed | Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title_short | Electrochemical oxidation of the phenolic benzotriazoles UV‐234 and UV‐327 in organic solvents |
| title_sort | electrochemical oxidation of the phenolic benzotriazoles uv 234 and uv 327 in organic solvents |
| topic | Science::Chemistry Electrochemical Oxidation Phenolic Benzotriazoles |
| url | https://hdl.handle.net/10356/139621 |
| work_keys_str_mv | AT chanyayun electrochemicaloxidationofthephenolicbenzotriazolesuv234anduv327inorganicsolvents AT websterricharddavid electrochemicaloxidationofthephenolicbenzotriazolesuv234anduv327inorganicsolvents |