12143-45-2Relevant academic research and scientific papers
Electron Spin Resonance and Pulse Radiolysis Studies on the Reaction of OH* and SO4*- with Five-Membered Heterocyclic Compounds in Aqueous Solution
Dogan, I.,Steenken, S.,Schulte-Frohlinde, D.,Icli, S.
, p. 1887 - 1894 (1990)
The reactions of several five-membered oxygen and nitrogen heterocycles with OH* and SO4*- radicals have been investigated in aqueous solution using in-situ radiolysis and photolysis ESR, and optical and conductometric pulse radiolys
Electron-transfer component in hydroxyl radical reactions observed by time resolved resonance raman spectroscopy
Tripathi
, p. 4161 - 4166 (1998)
The existence of an electron-transfer pathway in the reaction of ·OH radical with aromatic molecules in water has been established, for the first time, using time-resolved resonance Raman spectroscopy as a diagnostic tool and p-dimethoxybenzene as a model system. In the currently accepted mechanism, the cation radical is produced by ·OH addition to the ring, followed by loss of OH-. The present work demonstrates that this process competes with direct electron transfer. A generalized reaction mechanism has been proposed in terms of potential energy diagrams to explain two-step formation of the cation radical. In this reaction mechanism, the electron- transfer component and the rate of OH- elimination from the ·OH adduct both depend on the ionization potential (IP) of the molecule. The cation radical yield by electron transfer increases from 6% in p-dimethoxybenzene to 30% in p-anisidine and 85% in p-phenylenediamine. For neutral molecules with IP > 8 eV, the ·OH addition is the first step in the chemistry, and for IP 7 eV, it is the electron transfer. In the intermediate IP range, both processes occur simultaneously.
Pulse Radiolysis Study of Concentrated Sulfuric Acid Solutions; Formation Mechanism, Yield and Reactivity of Sulfate Radicals
Jiang, Pei-Yun,Katsumura, Yosuke,Nagaishi, Ryuji,Domae, Masahumi,Ishikawa, Kenichi,et al.
, p. 1653 - 1658 (1992)
In the pulse radiolysis of concentrated sulfuric acid solutions, the absorption spectrum and the molar absorption coefficient (1600 dm3 mol-1 cm-1) of the sulfate radical are unchanged up to 10 mol dm-3 H2SO4, suggesting that the sulfate radical exists in the dissociated form (SO4-).Two formation processes for the sulfate radical have been directly demonstrated in sulfuric acid and hydrogensulfate solutions: a fast one completed in the duration of the electron pulse, and a slow one occuring over a microsecond time range.For sulfate solutions only the fast formation process is observed.In sulfuric acid solutions the slow formation process is OH + HSO4- -> H2O + SO4- (4.7 x 105 dm3 mol-1 s-1) and OH + H2SO4 -> HSO4 + H2O -> SO4- + H3O+ (1,4 x 107 dm3 mol-1 s-1) and the fast formation process is the direct action of radiation on sulfuric acid with a G value of (2.7 +/- 0.4) x 10-2 molecule eV-1.The yields of (OH + SO4-) and H can be quantified as: G(OH + SO4-) = 2.9fw + 2.7fs and G(H) = 3.7fw + 2.7fs.The yields of SO4- have also been evaluated and the decay kinetics and reactions of the sulfate radical studied.
Temperature and ionic strength effects on some reactions involving sulfate radical [SO4-(aq)]
Bao, Zhen-Chuan,Barker, John R.
, p. 9780 - 9787 (1996)
Sulfate radical anion SO4- was generated by 248 nm laser flash photolysis of K2S2O8 solutions and monitored by time-resolved multipass absorbance at 454 nm. The 320-520 nm absorption spectrum of SO4- was unaffected by up to 2 M added HClO4, under the experimental conditions. Three reactions were investigated: (a) SO4- + SO4- → S2O82-, (b) SO4- + H2O → HSO4- + OH, and (c) SO4- + S2O82- → products. Rate constant kc was too slow to be measured, and only an upper limit was determined: kc ≤ 104 M-1 s-1. Arrhenius parameters were determined at low ionic strength over the range 11.8-74.4°C: 2ka/∈ = (4.8 ± 2.0) × 105 exp(-1.7 ± 1.1 kJ mol-1/RT) cm s-1 and kb = (4.7 ± 0.1) × 103 exp(-15.5 ± 0.6 kJ mol-1/RT) M-1 s-1, where ∈ is the SO4- absorption coefficient at 454 nm. At 296 K, the values are in good agreement with literature values: 2ka/∈ = (2.5 ± 0.2) × 105 cm s-1 and kb[H2O] = 440 ± 50 s-1. Rate constants ka and kb were found to increase strongly and nonlinearly with increasing ionic strength (added NaClO4) or acidity (added HClO4). Ion-pair formation provides a possible explanation, and a quantitative empirical model is presented for conditions with [Na+] ≤ 1.6 M and [H+] ≤ 3 M. Using the ion-pair model, estimated ionization equilibrium constants are obtained for the H+SO4- and the Na+SO4- radical ion pairs.
Generation and Reactions of the Chlorine Atom in Aqueous Solution
Gilbert, Bruce C.,Stell, Jonathan K.,Peet, Wendy J.,Radford, Karen J.
, p. 3319 - 3330 (1988)
The chlorine atom (Cl.) has been generated in aqueous solution by reaction of Cl- with SO4.- and H2PO4., obtained by metal-catalysed decomposition of the appropriate peroxides.E.s.r. experiments in conjuction with a fast-flow method establish that Cl. is highly reactive, readly undergoing rapid addition, hydrogen-abstraction and electron-transfer reactions (k = 108-109 dm3 mol-1 s-1).The factors which influence the observed selectivity (energetics and polar effects) are discussed.
The formation of SO5- by gas phase ion-molecule reactions
Moehler, O.,Reiner, T.,Arnold, F.
, p. 8233 - 8239 (1992)
A flow tube apparatus used to investigate the formation of SO5- ions by gas phase ion-molecule reactions.The reactions studied in an N2 buffer gas at 2.5 hPa pressure and room temperature (298 K) included SO2 and O2 reactions with O2-, O3-, CO3-, SO2-, and SO3- as well as their hydrates.Reaction rate constants were measured and the major product channels were identified for most reactions.The free energy changes for the hydration reactions of SO3-, SO4-, and SO5- were derived from equilibrium constant measurements.The present investigations clearly show that SO5- ions are formed in the gas phase by the association of O2 to SO3- and by the switching reaction of SO3-H2O with O2.An effective binary rate constant of 2.0*10-12 cm3 s-1 was measured for the association reaction at 2.5 hPa N2 and the rate constant of the switching reaction was 5.0*10-11 cm3 s-1.Also the reaction of O3-H2O with SO2 probably yields SO5- by a switching process having a rate constant of 1.8*10-9 cm3 s-1.The heat of formation of SO5- was estimated to be less than -715 kJ/mol.The present results have implications to the negative ion chemistry of the atmosphere and are important for measurements of atmospheric SO2 concentrations by chemical ionization mass spectrometry.
Transient intermediates in the laser flash photolysis of ketoprofen in aqueous solutions: Unusual photochemistry for the benzophenone chromophore
Martínez,Scaiano
, p. 11066 - 11070 (1997)
The transient intermediates the nanosecond laser flash photolysis of ketoprofen, an arylpropionic acid, show the formation of a carbanion in aqueous solutions at pH 7.1. This carbanion incorporates spectroscopic properties from both a ketyl radical anion and a benzylic radical. The ketoprofen carboxylate undergoes biphotonic photoionization, a process that contributes less than 10% to its photodecomposition- and leads to a benzylic-type radical after decarboxylation with a rate constant ≤1 x 107 s-1. On the other hand, the carbanion forms monophotonically and the unsuccessful attempts to sensitize the formation of the ketoprofen triplet excited state in aqueous solutions suggest that the carbanion precursor is either an excited singlet state or an extremely short-lived triplet. In organic solvents of lower polarity, the excited triplet state is readily detectable.
Kinetics and Mechanism of the Interaction of Potassium Peroxydisulfate and 18-Crown-6 in Aqueous Media
Rasmussen, Jerald K.,Heilmann, Steven M.,Toren, Paul E.,Pocius, Alphonsus V.,Kotnour, Thomas A.
, p. 6845 - 6849 (1983)
A kinetic investigation of the interaction of potassium peroxydisulfate with the crown ether 18-crown-6 in basic aqueous media has shown that the crown ether has a tremendous accelerating effect upon the rate of disappearance of peroxydisulfate.This acceleration is due in part to a radical chain mechanism in which crown is oxidized, and which is similar to that observed in the presence of simple ethers.However, an additional crown effect is observed which is explicable in terms of a Coulombic attraction between a cation-complexed crown radical and the peroxydisulfate dianion.
A kinetic study of the reactions of sulfate radicals at the silica nanoparticle - Water interface
Caregnato, Paula,Mora, Veroì?nica C.,Le Roux, Galo Carrillo,Maì?rtire, Daniel O.,Gonzalez, Moì?nica C.
, p. 6131 - 6138 (2003)
Sulfate radicals, SO4.-, were generated using flash photolysis of aqueous S2O82- solutions and the reactions of the inorganic radicals with the surface of suspended silica nanoparticles (NP) investigated. In the presence of colloidal silica no absorption traces due to SO4.- radicals are observed at 100 ??s after the flash of light. However, two transient species with absorption maxima around 320 and 600 nm are formed. A kinetic analysis of the experimental results indicate that SO4.- radicals are adsorbed on the NP surface, leading to the formation of an adduct, with ??max a?? 320 nm (?μ a?? 7000 cm-1 M-1), and showing similar reactivity to that observed for the sulfate radical in aqueous solutions. The NP - sulfate radical adducts react with adsorbed water, and with single and geminal SiO- sites with reaction rate constants of 1.5 ?? 1014 ?? e-(58?±12)kJ/mol)RT s-1, 3 ?? e-(2?±17)kJ/mol/RT s-1 and 11 ?? e-(46?±13)kJ/mol/RT s-1, respectively. Two different SiO. surface defects, showing similar spectra (??max a?? 600 nm) but different reactivities, are formed from the reaction of NP - sulfate radicals and deprotonated geminal and single silanols.
Reaction rate constants for O2-(H2O)n ions n=0 to 4, with O3, NO, SO2, and CO2
Fahey, D. W.,Boehringer, H.,Fehsenfeld, F. C.,Ferguson, E. E.
, p. 1799 - 1805 (1982)
Reaction rate constants for O2-(H2O)n ions with n=0 to 4 have been measured in a variable temperature flowing afterglow apparatus with a novel ion source configuration.The ios have been reacted with O3, NO, SO2, and CO2.The reaction with O3 is charge-transfer to produce O3- with simultaneous transfer of water ligands.The reactions with NO and SO2 are ligand switching reactions in which NO or SO2 displaces one or more water molecules clustered to O2- leaving NO3- and SO4- as core ions.In these cases, the reaction rate constants are not decreased measurably by an increase in n.CO2 rapidly displaces H2O in reaction with O2-(H2O) but does not react with O2-(H2O)3,4.Isotopically labelled O2- ions were used to elucidate several reaction mechanisms.The rapid destruction of O2-(H2O)4 ions by O3, NO, and SO2 insure that O2-(H2O)n ions cannot be dominant small air ions in the earth's lower atmosphere.
