Reactivity of H atoms and hydrated electrons with chlorobenzoic acids

Zona, Robert; Solar, Sonja; Getoff, N.; Sehested, Κ.; Holcman, Jerzy

doi:10.1016/j.radphyschem.2007.05.001

Cited by 24 publications

(22 citation statements)

References 20 publications

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“…In contrast to aliphatic chlorides, chloroarenes lose halogen in a consecutive mechanism . Their radical anions resulting from

e_{aq}^{• -}

capture live long enough for characterization before they cleave to give the chloride ion and a σ radical.…”

Section: Resultsmentioning

confidence: 99%

“…[9] In contrast to aliphatic chlorides,c hloroarenesl ose halogen in ac onsecutive mechanism. [33] Their radical anionsr esulting from e À aq capturel ive long enough for characterization before they cleave to give the chloride ion and a s radical. For the monochlorinated benzoates o-ClBz, m-ClBz, and p-ClBz, the cleavage rate constants differ widely (8 10 7 s À1 ,1 .2 10 6 s À1 , and 4 10 7 s À1 ), [33,34] whereas the rate constants of e À aq capture lie within am uch more narrow range (1.4 10 9 m À1 s À1 ,4 .8 10 9 m À1 s À1 ,a nd 6 10 9 m À1 s À1 ).…”

Section: Dehalogenationsmentioning

confidence: 99%

“…[33] Their radical anionsr esulting from e À aq capturel ive long enough for characterization before they cleave to give the chloride ion and a s radical. For the monochlorinated benzoates o-ClBz, m-ClBz, and p-ClBz, the cleavage rate constants differ widely (8 10 7 s À1 ,1 .2 10 6 s À1 , and 4 10 7 s À1 ), [33,34] whereas the rate constants of e À aq capture lie within am uch more narrow range (1.4 10 9 m À1 s À1 ,4 .8 10 9 m À1 s À1 ,a nd 6 10 9 m À1 s À1 ). [33] Progressive scavenging of e À aq by the reaction product benzoate (rate constant,3 .2 10 9 m À1 s À1 ) [7] complicates the kinetics but does not render the reactions elf-limiting because the benzoate radicala nion is thermodynamically capable of reducing the chlorinated substrates, which are less electron-rich than benzoate.…”

Section: Dehalogenationsmentioning

confidence: 99%

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Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light‐Emitting Diode

Naumann

Lehmann

Goez

2018

Chemistry A European J

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We have explored alkyl substitution of the ligands as a means to improve the performance of the title complexes in photoredox catalytic systems that produce synthetically useable amounts of hydrated electrons through photon pooling. Despite generating a super-reductant, these electron sources only consume the bioavailable ascorbate and are driven by a green light-emitting diode (LED). The substitutions influence the catalyst activity through the interplay of the quenching parameters, the recombination rate of the reduced catalyst OER and the ascorbyl radical across the micelle-water interface, and the quantum yield of OER photoionization. Laser flash photolysis yields comprehensive information on all these processes and allows quantitative predictions of the activity observed in LED kinetics, but the latter method provides the only access to the catalyst stability under illumination on the timescale of the syntheses. The homoleptic complex with dimethylbipyridine ligands emerges as the optimum that combines an activity twice as high with an undiminished stability in relation to the parent compound. With this complex, we have effected dehalogenations of alkyl and aryl chlorides and fluorides, hydrogenations of carbon-carbon double bonds, and self- as well as cross-coupling reactions. All the substrates employed are impervious to ordinary photoredox catalysts but present no problems to the hydrated electron as a super-reductant. A particularly attractive application is selective deuteration with high isotopic purity, which is achieved simply by using heavy water as the solvent.

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“…In contrast to aliphatic chlorides, chloroarenes lose halogen in a consecutive mechanism . Their radical anions resulting from

e_{aq}^{• -}

capture live long enough for characterization before they cleave to give the chloride ion and a σ radical.…”

Section: Resultsmentioning

confidence: 99%

Section: Dehalogenationsmentioning

confidence: 99%

Section: Dehalogenationsmentioning

confidence: 99%

See 1 more Smart Citation

Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light‐Emitting Diode

Naumann

Lehmann

Goez

2018

Chemistry A European J

View full text Add to dashboard Cite

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“…However, there was no transient absorption found for the methyl-2,2,3,3-tetrafluoropropyl ether reaction with this radical. This latter reaction-rate constant was therefore determined by competition kinetics using 200 µM para-chlorobenzoic acid (pCBA) as a standard: [13] …”

Section: Pulse Radiolysis Kinetic Measurementsmentioning

confidence: 99%

The Radiation Chemistry of the Cs-7SB Modifier used in Cs and Sr Solvent Extraction

Swancutt

Cullen

Mezyk

et al. 2011

Solvent Extraction and Ion Exchange

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The compound 1-(2,2,3,3,-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol, also called Cs-7SB, is used as a solvent modifier in formulations containing calixarenes and crown ethers for cesium and strontium extraction from nuclear waste solutions. The compound solvates complexes of both metals and decreases in its concentration result in lowered extraction efficiency for both. The use of Cs-7SB in nuclear-solvent extraction ensures that it will be exposed to high-radiation doses, and thus its radiation-chemical robustness is a matter of interest in the design of extraction systems employing it. The behavior of the compound in irradiated solution, both in the presence and absence of a nitric acid aqueous phase was investigated here using steady state-and pulsed-radiolysis techniques. The rate constants for the aqueous reactions of Cs-7SB with • H, • OH, • NO 3 , and • NO 2 radicals are reported. UPLC-UV-MS results were used to identify major products of the radiolysis of Cs-7SB in contact with nitric acid, and revealed the production of hydroxylated nitro-derivatives. Reaction mechanisms are proposed and it was concluded that the aryl-ether configuration of this molecule makes it especially susceptible to nitration in the presence of radiolytically-produced nitrous acid. Fluoride yields are also given under various conditions.

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“…The

e_{aq}^{• -}

attachment to an aryl chloride affords a radical anion with a lifetime on a sub‐μs timescale, which dissociates to give a chloride ion and an aryl σ radical . The further fate of this radical depends on the available reaction partners, with the three pathways and their implications as follows.…”

Section: Resultsmentioning

confidence: 99%

First Micelle‐Free Photoredox Catalytic Access to Hydrated Electrons for Syntheses and Remediations with a Visible LED or even Sunlight

Naumann

Goez

2018

Chemistry A European J

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Hydrated electrons are super-reductants, yet can be generated with visible light when two photons are pooled, most efficiently through storing the energy of the first photon in a radical pair formed by the reduction of an excited catalyst by a sacrificial donor. All previous such systems for producing synthetically useable amounts of hydrated electrons with an LED in the visible range had to resort to compartmentalization by SDS micelles to curb the performance-limiting recombination of the pair. To overcome micelle-imposed constraints on sustainability and applications, we have instead attached carboxylate groups to a ruthenium (tris)bipyridyl catalyst such that its pentaanionic radical strongly repels the dianionic radical of the bioavailable donor urate. We have explored the influence of the Coulombic interactions on the electron generation by a time-resolved study from microseconds to hours, including for comparison the unsubstituted complex, which forms a monocationic radical, with and without SDS micelles. The new homogeneous electron source is best with regard to stability and total electron output; it has a broader synthetic scope because it does not entail micellar shielding of less hydrophilic compounds, which particularly facilitates cross-couplings; and it tolerates supramolecular containers as carriers of water-insoluble substrates or products. As an application in the field, we demonstrate the solar remediation of a recalcitrant chloro-organic bulk chemical.

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Reactivity of H atoms and hydrated electrons with chlorobenzoic acids

Cited by 24 publications

References 20 publications

Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light‐Emitting Diode

Micellized Tris(bipyridine)ruthenium Catalysts Affording Preparative Amounts of Hydrated Electrons with a Green Light‐Emitting Diode

The Radiation Chemistry of the Cs-7SB Modifier used in Cs and Sr Solvent Extraction

First Micelle‐Free Photoredox Catalytic Access to Hydrated Electrons for Syntheses and Remediations with a Visible LED or even Sunlight

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