Advanced oxidation process of coumarins by hydroxyl radical: Towards the new mechanism leading to less toxic products

Milenković, Dejan; Dimić, Dušan; Avdović, Edina H.; Amić, Ana; Marković, Jasmina M. Dimitrić; Marković, Zoran

doi:10.1016/j.cej.2020.124971

Cited by 62 publications

(30 citation statements)

References 59 publications

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“…Three antioxidant mechanisms were selected for the evaluation of the antioxidant activity: Hydrogen Atom Transfer (HAT), Single-Electron Transfer followed by Proton Transfer (SET-PT), and Sequential Proton Loss-Electron Transfer (SPLET) [28][29][30][31].…”

Section: Methodsmentioning

confidence: 99%

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Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

et al. 2021

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Compounds from the plant world that possess antioxidant abilities are of special importance for the food and pharmaceutical industry. Coumarins are a large, widely distributed group of natural compounds, usually found in plants, often with good antioxidant capacity. The coumarin-hydroxybenzohydrazide derivatives were synthesized using a green, one-pot protocol. This procedure includes the use of an environmentally benign mixture (vinegar and ethanol) as a catalyst and solvent, as well as very easy isolation of the desired products. The obtained compounds were structurally characterized by IR and NMR spectroscopy. The purity of all compounds was determined by HPLC and by elemental microanalysis. In addition, these compounds were evaluated for their in vitro antioxidant activity. Mechanisms of antioxidative activity were theoretically investigated by the density functional theory approach and the calculated values of various thermodynamic parameters, such as bond dissociation enthalpy, proton affinity, frontier molecular orbitals, and ionization potential. In silico calculations indicated that hydrogen atom transfer and sequential proton loss–electron transfer reaction mechanisms are probable, in non-polar and polar solvents respectively. Additionally, it was found that the single-electron transfer followed by proton transfer was not an operative mechanism in either solvent. The conducted tests indicate the excellent antioxidant activity, as well as the low potential toxicity, of the investigated compounds, which makes them good candidates for potential use in food chemistry.

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Section: Methodsmentioning

confidence: 99%

“…The abstraction of hydrogen atoms can be described by two mechanisms, HAT and Proton-Coupled Electron Transfer (PCET) [29]. The HAT mechanism is defined as the simultaneous transfer of an electron and a proton between the donor and acceptor.…”

Section: Methodsmentioning

confidence: 99%

Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

et al. 2021

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“…Routes involving the removal of allylic hydrogens from C3 and C6 (4.2–9.6 kJ mol −1 ) are clearly preferred over those implying non-allylic atoms C4 and C5 (33.4–34.8 kJ mol −1 ), in agreement with the relative acidity of allylic hydrogens. When routes leading to conjugated tetrachlorocyclohexadienes are compared, a preference for the formation of 5 (involving allylic proton removal) relative to 2 (implying non-allylic hydrogen abstraction) by a 200,000:1 ratio (according to calculated relative rate constants 23 ) is found.…”

Section: Resultsmentioning

confidence: 99%

Theoretical insight on the treatment of β-hexachlorocyclohexane waste through alkaline dehydrochlorination

Bescós

Herrerı́as

Hormigón

et al. 2021

Sci Rep

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The occurrence of 4.8–7.2 million tons of hexachlorocyclohexane (HCH) isomers stocked in dumpsites around the world constitutes a huge environmental and economical challenge because of their toxicity and persistence. Alkaline treatment of an HCH mixture in a dehydrochlorination reaction is hampered by the low reactivity of the β-HCH isomer (HCl elimination unavoidably occurring through syn H–C–C–Cl arrangements). More intriguingly, the preferential formation of 1,2,4-trichlorobenzene in the β-HCH dehydrochlorination reaction (despite the larger thermodynamical stability of the 1,3,5-isomer) has remained unexplained up to now, though several kinetic studies had been reported. In this paper, we firstly show a detailed Density Functional study on all paths for the hydroxide anion-induced elimination of β-HCH through a three-stage reaction mechanism (involving two types of reaction intermediates). We have now demonstrated that the first reaction intermediate can follow several alternative paths, the preferred route involving abstraction of the most acidic allylic hydrogen which leads to a second reaction intermediate yielding only 1,2,4-trichlorobenzene as the final reaction product. Our theoretical results allow explaining the available experimental data on the β-HCH dehydrochlorination reaction (rate-determining step, regioselectivity, instability of some reaction intermediates).

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“…This phenomenon has been observed in numerous organic, inorganic, and organometallic reactions, 64,65 and for the rst time has been recently employed in the examination of antioxidative mechanisms. 44,66 The phenomenon involves the participation of spin-crossing effects for the elucidation of rate constants, branching ratios and reaction mechanisms. Radical adduct formation in the position 6-C of THB-Oc was selected as representative of the RAF pathways, and the HO-C6 distance was chosen as the scan coordinate.…”

Section: Kinetic Approachmentioning

confidence: 99%

Comparison of the scavenging capacities of phloroglucinol and 2,4,6-trihydroxypyridine towards HO˙ radical: a computational study

et al. 2020

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Advanced oxidation process of coumarins by hydroxyl radical: Towards the new mechanism leading to less toxic products

Cited by 62 publications

References 59 publications

Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

Green One-Pot Synthesis of Coumarin-Hydroxybenzohydrazide Hybrids and Their Antioxidant Potency

Theoretical insight on the treatment of β-hexachlorocyclohexane waste through alkaline dehydrochlorination

Comparison of the scavenging capacities of phloroglucinol and 2,4,6-trihydroxypyridine towards HO˙ radical: a computational study

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