Radiation-induced redox reactions of 2-, 3- and 4-amino-phenols in aqueous solutions

Dwibedy, P.; Dey, G.R.; Naik, D.B.; Kishore, Kamal

doi:10.1016/j.radphyschem.2004.12.007

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…The absorbance above 400 nm can be attributed to reactions on the 4-aminophenol part of AQ in agreement with results on 4-aminophenol and acetaminophen [2,8,14]. OH reaction in these molecules produces 4-aminophenoxy radical with k max % 440 nm and e max % 5000 mol À1 dm 3 cm À1 [7,8]. The increasing absorbance above 400 nm after the AQ þ OH reaction is completed is due to transformation of the first formed hydroxycyclohexadienyl radical (c, Scheme 1) to aminophenoxy radical (d) with a rate constant of 2 Â 10 5 s À1 .…”

Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentssupporting

confidence: 89%

“…The radical adducts on Cl-quinoline (a, Scheme 1) and 4-aminophenol (c) parts of AQ are expected to exhibit transient absorption between 300 and 400 nm as it is typical for aromatic adduct (hydroxycyclohexadienyl) radicals [8]. Due to the strong absorbance of AQ in this range, we did not take the transient spectrum at wavelengths below 400 nm.…”

Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentsmentioning

confidence: 99%

“…The reactivity with the aminophenol part is probably low. p-Aminophenol and acetaminophen react with e aq À with rate constants of 2.5 Â 10 8 and 5 Â 10 8 mol À1 dm 3 s À1 , respectively [8,14]; the rate constants of alkylamines are also in the few times 10 9 mol À1 dm 3 s À1 range [35].…”

Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentsmentioning

confidence: 99%

“…Using pulse radiolysis technique, the radical reactions of AQ were studied by Bisby [2]. However, the radical reactions of its structural unit 4-aminophenol [7,8] and also of the analgesic and antipyretic type drug molecule acetaminophen (paracetamol) [9][10][11][12][13][14] were investigated by several research groups. The hydroxyl radicals in their reactions with the aromatic molecules generally add to the conjugated ring, direct oxidation (i.e.…”

Section: Introductionmentioning

confidence: 99%

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High-energy ionizing radiation-induced degradation of amodiaquine in dilute aqueous solution: radical reactions and kinetics

Kovács

Simon

Balogh

et al. 2020

Free Radical Research

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The widely used antimalarial drug amodiaquine (AQ) contains a 7-Cl-quinoline unit, a substituted 4-aminophenol part connected through the amino group and a tertiary amine part. The 4-aminophenol unit can be easily oxidized through radical intermediates to iminoquinone. This reaction also takes place in vitro and in vivo enzymatic reactions. The reaction is expected to have an important role in degradation of AQ in surface waters and also during degradation in advanced oxidation processes. In this paper by means of radiation chemical techniques the one-electron oxidation and reduction of AQ were studied using transient kinetics, kinetics of AQ degradation, formation and decay of end-products of radical reactions. The hydroxyl radicals were shown to add both to the quinoline ($ 38%) and aminophenol ($ 50%) parts via formation of hydroxycyclohexadienyl radicals and by H-abstraction or by an electron removal from the tertiary amine part of the molecule ($ 12%). The dihydroxycyclohexadienyl radical formed on the aminophenol part is suggested to transform to aminophenoxy radical. The hydrated electrons can also effectively contribute to AQ degradation. Chemical oxygen demand and total organic carbon content investigations were also made in order to characterize the ionizing radiation-induced oxidation and mineralization. In aerated 0.1 mmol dm À3 solution, at 2.5 kGy absorbed dose AQ and its higher molecular mass degradation products demolished completely. Ionizing irradiation is a capable technique for degradation of AQ under both oxidative and reductive circumstances.

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Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentssupporting

confidence: 89%

Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentsmentioning

confidence: 99%

Section: Uv-vis Absorption Spectra Of Amodiaquine In C-radiolysis and Pulse Radiolysis Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

High-energy ionizing radiation-induced degradation of amodiaquine in dilute aqueous solution: radical reactions and kinetics

Kovács

Simon

Balogh

et al. 2020

Free Radical Research

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“…Aniline cation reacts in direct oxidation with k Cl2•-= 1.2 × 10 7 M -1 s -1 (Hasegawa and Neta 1978). An OH group added to aniline in meta-position (Scheme 6S) in 3-amino-phenol (3-APH + ) increases k Cl2•-to 3.6 × 10 8 M -1 s -1 (Dwibedy et al 2005): in the reaction phenoxyl radical forms just as in reactions of other one-electron oxidants. There is no reaction between Br 2 •and 3-APH + indicating a reduction potential of the 3-AP • ,H + /3-APH + couple between 2.1 and 1.63 V vs.…”

Section: Anilinesmentioning

confidence: 99%

Rate constants of dichloride radical anion reactions with molecules of environmental interest in aqueous solution: a review

Wojnárovits

Takács

2021

Environ Sci Pollut Res

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Natural waters, water droplets in the air at coastal regions and wastewaters usually contain chloride ions (Cl-) in relatively high concentrations in the milimolar range. In the reactions of highly oxidizing radicals (e.g., •OH, •NO3, or SO4•-) in the nature or during wastewater treatment in advanced oxidation processes the chloride ions easily transform to chlorine containing radicals, such as Cl•, Cl2•-, and ClO•. This transformation basically affects the degradation of organic molecules. In this review about 400 rate constants of the dichloride radical anion (Cl2•-) with about 300 organic molecules is discussed together with the reaction mechanisms. The reactions with phenols, anilines, sulfur compounds (with sulfur atom in lower oxidation state), and molecules with conjugated electron systems are suggested to take place with electron transfer mechanism. The rate constant is high (107–109 M-1 s-1) when the reduction potential the one-electron oxidized species/molecule couple is well below that of the Cl2•-/2Cl- couple.

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The Chemical Background of Advanced Oxidation Processes

Csay

Homlok

Illés

et al. 2014

Israel Journal of Chemistry

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In advanced oxidation processes, the hydroxyl radical is the main initiator of the degradation of pollutants. For aromatic molecules, the rate coefficients are between 2×109 and 1×1010 mol−1 dm3 s−1 and show some variation according to the electron‐withdrawing or donating nature of the substituents. The one‐electron oxidant .OH induces 2–4 electron oxidations of many aromatic pollutants. These high rates are explained by .OH addition to an unsaturated bond, scavenging of the organic radical by dissolved O2, and subsequent reactions. In amino‐substituted molecules and in azo dyes the efficiency is lower, because O2 cannot compete efficiently with the unimolecular transformation of carbon‐centered radicals. Generally, the toxicity first increases and then decreases with treatment time. The increase is attributed to the high toxicity of some degradation products and to H2O2 formation. In surface waters, traces of transition metal ions degrade some of the H2O2 in Fenton‐like processes.

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Radiation-induced redox reactions of 2-, 3- and 4-amino-phenols in aqueous solutions

Cited by 7 publications

References 18 publications

High-energy ionizing radiation-induced degradation of amodiaquine in dilute aqueous solution: radical reactions and kinetics

High-energy ionizing radiation-induced degradation of amodiaquine in dilute aqueous solution: radical reactions and kinetics

Rate constants of dichloride radical anion reactions with molecules of environmental interest in aqueous solution: a review

The Chemical Background of Advanced Oxidation Processes

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