ChemInform Abstract: Photoreactivity of Hydroquinone in Aqueous Solution.

Boule, Pierre; Rossi, A; Pilichowski, Jean‐François

doi:10.1002/chin.199316107

Cited by 7 publications

(26 citation statements)

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“…Interestingly, a two-stage phototransformation process was observed in the air-saturated solutions ([O 2 ] = 0.28 mM) when the concentrations of AA and QH 2 were in the range of 0.1–0.2 mM (Figure c). The thermal reaction of QH 2 is sensitive to solution pH, with the deprotonated form of QH 2 usually being more reactive than the protonated species . After irradiation, the solution pH had decreased from 5.8 to around 4.0 (depending on the concentration of AA) (Figure d).…”

Section: Resultsmentioning

confidence: 99%

“…The reactivity of quinones in aquatic media has been extensively studied from various perspectives, including their phototransformation − and role as electron shuttles (redox mediators) in natural and engineered systems. ,− As electron shuttles, quinones can produce reactive oxygen species (ROS) in photochemical redox cycling via either oxidation of water or reduction of dissolved oxygen (DO). − The ROS generated from quinones mediates a wide range of environmental redox processes in the subsurface, soils, sediments, and surface and atmospheric waters. − …”

Section: Introductionmentioning

confidence: 99%

“…So far, more attention has been paid to the phototransformation of quinones than quinols. − In a recent work, it was found that hydroquinone (QH 2 ) is more photochemically stable than 1,4-benzoquinone (BQ). Under identical conditions (0.5 mM quinones, pH 6.8, air-saturated, 4.0–7.1 mW/cm 2 at 365 nm, medium-pressure mercury lamp), the pseudo-first-order rate constant ( k 1 ) of QH 2 was in the range of 0.002–0.032 min –1 , whereas the k 1 of BQ was in the range of 0.39–1.01 min –1 .…”

Section: Introductionmentioning

confidence: 99%

“…Although the photochemistry of QH 2 and AA has been investigated individually, ,,− it is still unclear what will happen if QH 2 and AA coexist in a solution. Specifically, both QH 2 and AA are known as electron shuttles, but it is not clear which will act as the electron donor and which will act as the acceptor under UV irradiation.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Photooxidation of Hydroquinone by Acetylacetone, a Novel Photosensitizer and Electron Shuttle

Jin

Zhang

et al. 2019

Environ. Sci. Technol.

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Quinones are important electron shuttles as well as micropollutants in the nature. Acetylacetone (AA) is a newly recognized electron shuttle in aqueous media exposed to UV irradiation. Herein, we studied the interactions between AA and hydroquinone (QH 2 ) under steady-state and transient photochemical conditions to clarify the possible reactions and consequences if QH 2 and AA coexist in a solution. Steady-state experimental results demonstrate that the interactions between AA and QH 2 were strongly affected by dissolved oxygen. In O 2 -rich solutions, the phototransformation of QH 2 was AA-independent. Both QH 2 and AA utilize O 2 as the electron acceptor, but in O 2 -insufficient solutions, AA became an important electron acceptor for the oxidation of QH 2 . In all cases, the coexistence of AA increased the phototransformation of QH 2 , whereas the decomposition of AA in O 2saturated and oversaturated solutions was inhibited by the presence of QH 2 . The underlying mechanisms were investigated by a combination of laser flash photolysis (LFP) and reduction potential analysis. The LFP results show that the excited AA serves as a better electron shuttle than QH 2 . As a consequence, AA might regulate the redox cycling of quinones, leading to significant effects on many processes, ranging from photosynthesis and respiration to photodegradation.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced Photooxidation of Hydroquinone by Acetylacetone, a Novel Photosensitizer and Electron Shuttle

Jin

Zhang

et al. 2019

Environ. Sci. Technol.

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“…The latter compound was used as sensitizer as benzophenone and acetophenone were not sufficiently water soluble under our experimental conditions. Under excitation, hydroquinone is known to generate its triplet excited state with a quantum yield of 0.39 (28). Steady-state irradiation of hydroquinone (9.0 · 10 )4 mol L )1 ) using a monochromatic light at 300 nm in the presence of CYA (2.3 · 10 )4 mol L )1 ) was performed in aqueous solution.…”

Section: Photosensitized Processmentioning

confidence: 99%

Reaction Pathways for the Photodegradation of the Organophosphorus Cyanophos in Aqueous Solutions

Ménager¹,

Pilichowski²,

Sarakha³

2010

Photochem & Photobiology

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Photodegradation in aqueous solutions is an important pathway for many agrochemicals such as pesticides. In the present work, the photochemical transformation of cyanophos (CYA) was investigated in aqueous solutions using UV light within the 254-313 nm range as well as solar light. The study was performed in order to have a deep insight into the mechanistic pathways for the photochemical disappearance of CYA. Upon UV irradiation of an aerated solution of CYA, the degradation quantum yield was found equal to 1.8 x 10(-2). It is independent of the excitation wavelength but varies with oxygen concentration. It increased by a factor of 2 from oxygen-saturated to oxygen-free solution. Photosensitized experiments were performed using acrylamide and hydroquinone as energy acceptor and energy donor substrates, respectively. They show that both singlet and triplet excited states were involved in the photochemical behavior of CYA. The laser flash photolysis experiments clearly showed the involvement of the triplet excited state which was efficiently quenched by molecular oxygen and acrylamide with the rate constants 1.97 x 10(9) and 2.71 x 10(9) mol(-1) L s(-1), respectively. The photoproducts structures were proposed according to the mass spectral data using the LC/MS technique. The analytical study shows that various processes such as hydrolysis, homolytic bond dissociations and Photo-Fries process occur.

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Redox Conversion of Arsenite and Nitrate in the UV/Quinone Systems

Chen

Jin

Song

et al. 2018

Environ. Sci. Technol.

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Whether superoxide radical anion (O) was a key reactive species in the oxidation of arsenite (As(III)) in photochemical processes has long been a controversial issue. With hydroquinone (BQH) and 1,4-benzoquinone (BQ) as redox mediators, the photochemical oxidation of As(III) and reduction of nitrate (NO) was carefully investigated. O, singlet oxygen (O), HO, and semiquinone radical (BQH) were all possible reactive species in the irradiated system. However, since the formation of As(IV) is a necessary step in the oxidation of As(III), taking the standard reduction potentials into account, the reactions between the above species and As(III) were thermodynamically unfavorable. On the basis of radical scavenging experiments, hydroxyl radical (OH) was proved as the key species that led to the oxidation of As(III) in the UV/BQH system. It should be noted that the OH radicals were generated from the photolysis of HO, which came from the disproportionation of O and the reaction of O with BQH. Both the photoejected e from (BQH)* and the direct electron transfer with (BQH)* contributed to the reduction of NO in the UV/BQH process. No synergistic effect was observed in the redox conversion of As(III) and NO, further demonstrating that the role of BQH was negligible in the studied systems. The results here are helpful for a better understanding of the photochemical behaviors of quinones in the aquatic environment.

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ChemInform Abstract: Photoreactivity of Hydroquinone in Aqueous Solution.

Cited by 7 publications

References 0 publications

Enhanced Photooxidation of Hydroquinone by Acetylacetone, a Novel Photosensitizer and Electron Shuttle

Enhanced Photooxidation of Hydroquinone by Acetylacetone, a Novel Photosensitizer and Electron Shuttle

Reaction Pathways for the Photodegradation of the Organophosphorus Cyanophos in Aqueous Solutions

Redox Conversion of Arsenite and Nitrate in the UV/Quinone Systems

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