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1.
Absolute rate constants for hydroxyl radical, azide radical, and hydrated electron reactions with a sulfa drug 4,4'‐diamino diphenyl sulfone (dapsone) in water have been evaluated using electron pulse radiolysis technique. Absolute rate constants for hydroxyl radical and azide radical were determined as (8.4 ± 0.3) × 109 and (5.6 ± 0.5) × 109 M?1 s?1, respectively. The reduction of dapsone with the hydrated electron occurred with rate constant of (9.2 ± 0.1) × 109 M?1 s?1. Hydroxyl radical reactions result in the synchronous formation of adduct as well as anilino radical. The interesting observation is that the yield of the anilino radical increases with increase in pH. Contrary to this, the yield of the adduct decreases with pH. We propose that hydroxyl radical adds predominantly to the aniline. In contrast, the reaction of azide radical with the dapsone suggests that the reaction occurs at the –NH2 moiety of the aniline ring. The free radical electron transfer from dapsone to parent radical cation of non‐polar solvent also results in the formation of anilino radical only suggesting that the radical cation of dapsone has a short lifetime. The reaction of hydrated electrons with the dapsone suggests that the reaction occurs at different reaction site. The experimental results supported by theoretical calculations of this study provide fundamental mechanistic parameters that probably decide the fate of the radical cation of aniline derivatives. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
2.
Ridhima Chadha H. S. Mahal Tulsi Mukherjee S. Kapoor 《Journal of Physical Organic Chemistry》2009,22(4):349-354
The reactions of 3‐hydroxyanthranilic acid (3‐OHAA) with N3?, NO2?, NO?, CCl3O2? , and OH? radicals were examined using a pulse radiolysis technique mainly at pH 7. The bimolecular electron transfer from secondary one‐electron oxidants results in the formation of anilino radical (λmax ? 380 nm). The rate constant for the reaction of N3? radical with 3‐OHAA at pH 7 was found to be 6.3 × 109 dm3 mol?1 s?1. It was observed that the 3‐OHAA reacts with oxygen centered radicals. The repair rate constant for the electron transfer reaction from 3‐OHAA to guanosine radical and chlorpromazine cation radical was also examined using a pulse radiolysis technique. Kinetic studies indicate that 3‐OHAA may act as an antioxidant to repair free‐radical damage to above mentioned biologically important compounds. The rate constants of electron transfer from the 3‐OHAA to the guanosine and chlorpromazine radicals were determined. The one‐electron reduction potential for 3‐OHAA radical was found to be 0.53 ± 0.06 V versus NHE. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
3.
K. P. Prasanthkumar Cherumuttathu H. Suresh C. T. Aravindakumar 《Journal of Physical Organic Chemistry》2013,26(6):510-516
Pulse radiolysis with optical absorption detection has been used to study the reactions of hydroxyl radical (OH?) with 4‐thiouracil (4TU) in aqueous medium. The transient absorption spectrum for the reaction of OH? with 4TU is characterized by λmax 460 nm at pH 7. A second‐order rate constant k(4TU+OH) of 1.7 × 1010 M?1 s?1 is determined via competition kinetics method. The transient is envisaged as a dimer radical cation [4TU]2?+, formed via the reaction of an initially formed radical cation [4TU]?+ with another 4TU. The formation constant of [4TU]2?+ is 1.8 × 104 M?1. The reactions of dibromine radical ion (Br2??) at pH 7, dichlorine radical ion (Cl2??) at pH 1, and azide radical (N3?) at pH 7 with 4TU have also produced transient with λmax 460 nm. Density functional theory (DFT) studies at BHandHLYP/6–311 + G(d,p) level in aqueous phase showed that [4TU]2?+ is characterized by a two‐centerthree electron (2c‐3e) [?S∴S?] bond. The interaction energy of [?S∴S?] bond in [4TU]2?+ is ?13.01 kcal mol?1. The predicted λmax 457 nm by using the time‐dependent DFT method for [4TU]2?+ is in agreement with experimental λmax. Theoretical calculations also predicted that compared with [4TU]2?+, 4‐thiouridine dimer is more stable, whereas 4‐thiothymine dimer is less stable. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
Yong Du Jiadan Xue Chensheng Ma Wai Ming Kwok David Lee Phillips 《Journal of Raman spectroscopy : JRS》2008,39(4):503-514
A nanosecond time‐resolved resonance Raman (ns‐TR3) spectroscopic investigation of the intermolecular hydrogen‐abstraction reaction of the triplet state of 4‐benzoylpyridine (4‐BPy) in 2‐propanol solvent is reported. The TR3 results reveal a rapid hydrogen abstraction (<10 ns) by the 4‐BPy triplet state (nπ*) with the 2‐propanol solvent, leading to formation of a 4‐BPy ketyl radical and an associated dimethyl ketyl radical partner from the solvent. The recombination of these two radical species occurs with a time constant about 200 ns to produce a para‐N‐LAT (light absorbing transient). The structure, major spectral features, and identification of the ketyl radical and the para‐N‐LAT coupling complex have been determined and confirmed by comparison of the TR3 results with results from density functional theory (DFT) calculations. A reaction pathway for the photolysis of 4‐BPy in 2‐propanol deduced from the TR3 results is also presented. The electron‐withdrawing effect of the heterocyclic nitrogen for 4‐BPy on the triplet state makes it have a significantly higher chemical reactivity for the hydrogen abstraction with 2‐propanol compared to the previously reported corresponding benzophenone triplet reaction under similar reaction conditions. In addition, the 4‐BPy ketyl radical reacts with the dimethyl ketyl radical to attach at the para‐N atom position of the pyridine ring to form a cross‐coupling product such as 2‐[4‐(hydroxy‐phenyl‐methylene)‐4h‐pyridin‐1‐yl]‐propan‐2‐ol instead of attacking at the para‐C atom position as was observed for the corresponding benzophenone reaction reported in an earlier study. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
5.
Naduvilpurakkal B. Shibin Radhakrishnan Sreekanth Usha K. Aravind Kadavilpparampu M. Afsal Mohammed Narayana V. Chandrashekhar Jayan Joseph Sisir K. Sarkar Devidas B. Naik Charuvila T. Aravindakumar 《Journal of Physical Organic Chemistry》2014,27(6):478-483
Free radical‐induced oxidation reactions of glucosamine naphthalene acetic acid (GNaa) and naphthalene acetic acid (Naa) have been studied using pulse radiolysis. GNaa was synthesized by covalently attaching Naa on glucosamine. Hydroxyl adduct (from the reaction of hydroxyl radicals (●OH) at the naphthalene ring) was identified as the major transient intermediate (suggesting that the ●OH reaction is on the naphthalene ring) and is characterized by its absorption maxima of 340 and 400 nm. Both GNaa and Naa undergo similar reaction pattern. The bimolecular rate constants determined for the reactions are 4.8 × 109 and 8.9 × 109 dm3 mol?1 s?1 for GNaa and Naa respectively. The mechanism of reaction of ●OH with GNaa was further confirmed using steady‐state method. Radical cation of GNaa was detected as an intermediate during the reaction of sulfate radical (SO4●?) with GNaa (k2 = 4.52 × 109 dm3 mol?1 s?1). This radical cation transforms to a ●OH adduct at higher pH. The radical cation of GNaa is comparatively long lived, and a cyclic transition state by neighboring group participation accounts for its stability. The oxy radical anion (O●?) reacts with GNaa (k2 = 1.12 × 109 dm3 mol?1 s?1) mainly by one‐electron transfer mechanism. The reduction potential values of Naa and GNaa were determined using cyclic voltammetric technique, and these are 1.39 V versus NHE for Naa and 1.60 V versus NHE for GNaa. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
6.
Reaction mechanism of 2‐methoxyphenol (2MP) (guaiacol) with OH radical has been performed using density functional theory methods BH&HLYP and MPW1K method with 6‐311++G(d,p) basis set. Single‐point energy calculations were done using CCSD(T)/6‐311++G(d,p). The theoretical results reveal that the hydrogen abstraction from methoxy group is found to be the dominant reaction channel with an energy barrier of 9.31 kcal/mol. Also, time‐dependent density functional theory calculations have been performed using BH&HLYP/6‐311++G(d,p) level of theory, and the results reveal that the reactions occur in ground state than the excited state. The results of reaction force profile indicate that structural rearrangements are most influential with high percentage than the relaxation process. The calculated theoretical rate constants (12.19 × 10?11 cm3 molecule?1 s?1) are in good agreement with the experimental rate constant. The atmospheric lifetime of 2‐methoxyphenol with respect to OH radicals is 2.27 hours, which implies that OH radical plays an important role in the degradation of 2MP. The Wiberg bond index of the abstraction reaction reveals that the bond order is concerted, partially synchronic. The reactant‐like transition state satisfies Hammond postulate, which eventually results in an exothermic reaction, and the product‐like transition state reveals in endothermic nature. 相似文献
7.
Photoinduced electron transfer (PET) was studied in toluene solutions of the Pd-porphyrin-quinone (Pd-PQ) dyad by flash photolysis
in the picosecond time range and by a luminescence method. It is found that Pd-PQ has a high rate of intercombination conversion
Kisc=(7.7±0.2)·1010 sec−1. Competing intramolecular PET occurs from the lower excited singlet state of the dyad with the rate constant K
et
s
=(2.7 ±0.3)·1010 sec−1. Therefore, ∼74% of excited molecules from the dyad make a transition to the triplet T1 state and 26% take part in intramolecular PET resulting in formation of radical products. The radical products relax to the
ground state with the rate constant K=(7.4±0.2)·109 sec−1.
Institute of Molecular and Atomic Physics of the National Academy of Sciences of Belarus, 70, F. Skorina St., Minsk, 220072,
Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 11–18, January–February, 1999. 相似文献
8.
P. Manoj K. P. Prasanthkumar V. M. Manoj Usha K. Aravind T. K. Manojkumar C. T. Aravindakumar 《Journal of Physical Organic Chemistry》2007,20(2):122-129
Laser flash photolysis has been used to determine the bimolecular rate constants and the spectral nature of the intermediates obtained by the reaction of sulfate radical anion (SO) with 1,3,5‐triazine (T), 2,4,6‐trimethoxy‐1,3,5‐triazine (TMT), 2,4‐dioxohexahydro‐1,3,5‐triazine (DHT), and 6‐chloro N‐ethyl N'‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine (atrazine, AT). The rate constants determined were in the range 4.6 × 107–3 × 109 dm3 mol?1 s?1 at pH 6. The transient absorption spectra obtained from the reaction of SO with T, TMT, DHT and AT has an absorption maximum in the region 320–350 nm and was found to undergo second‐order decay. The intermediate species is assigned to N‐yl C(OH) radical of T (TOH?), carbon centered neutral radical of TMT, an OH‐adduct of AT and an N‐centered radical in the case of DHT. The interpretations on the experimental results obtained from TMT are supported by DFT calculation using Gaussian 03. Steady state radiolysis technique has also been used to investigate the degradation of AT induced by SO. The degradation profile indicated that about 99% of AT has been decomposed after an absorbed gamma‐radiation dose of 7.5 kGy. The degradation yield of AT (expressed as G(‐AT)) was found to be 0.26 µ mol J?1. The degradation reactions initiated by SO may thus be employed as a potential alternative for ?OH‐induced degradation of triazines. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
9.
Reactions of . OH/O .? radicals, H‐atoms as well as specific oxidants such as N and Cl radicals with 4‐hydroxybenzyl alcohol (4‐HBA) in aqueous solutions have been investigated at various pH values using the pulse radiolysis technique. At pH 6.8, . OH radicals were found to react with 4‐HBA (k = 6 × 109 dm3 mol?1 s?1) mainly by contributing to the phenyl moiety and to a minor extent by H‐abstraction from the ? CH2OH group. . OH radical adduct species of 4‐HBA, i.e., . OH‐(4‐HBA) formed in the addition reaction were found to undergo dehydration to give phenoxyl radicals of 4‐HBA. Decay rate of the adduct species was found to vary with pH. At pH 6.8, decay was very much dependent on phosphate buffer ion concentrations. Formation rate of phenoxyl radicals was found to increase with phosphate buffer ion concentration and reached a plateau value of 1.6 × 105 s?1 at a concentration of 0.04 mol dm?3 of each buffering ion. It was also seen that . OH‐(4‐HBA) adduct species react with HPO ions with a rate constant of 3.7 × 107 dm3 mol?1 s?1 and there was no such reaction with H2PO ions. However, the rate of reaction of . OH‐(4‐HBA) adduct species with HPO ions decreased on adding KH2PO4 to the solution containing a fixed concentration of Na2HPO4 which indicated an equilibrium in the H+ removal from . OH‐(4‐HBA) adduct species in the presence of phosphate ions. In the acidic region, the . OH‐(4‐HBA) adduct species were found to react with H+ ions with a rate constant of 2.5 × 107 dm3 mol?1 s?1. At pH 1, in the reaction of . OH radicals with 4‐HBA (k = 8.8 × 109 dm3 mol?1 s?1), the spectrum of the transient species formed was similar to that of phenoxyl radicals formed in the reaction of Cl radicals with 4‐HBA at pH 1 (k = 2.3 × 108 dm3 mol?1 s?1) showing that . OH radicals quantitatively bring about one electron oxidation of 4‐HBA. Reaction of . OH/O .? radicals with 4‐HBA by H‐abstraction mechanism at neutral and alkaline pH values gave reducing radicals and the proportion of the same was determined by following the extent of electron transfer to methyl viologen. H‐atom abstraction is the major pathway in the reaction of O .? radicals with 4‐HBA compared to the reaction of . OH radicals with 4‐HBA. At pH 1, transient species formed in the reactions of H‐atoms with 4‐HBA (k = 2.1 × 109 dm3 mol?1 s?1) were found to transfer electrons to methyl viologen quantitatively. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
10.
Plaban Jyoti Sarma Debojyoti Bhattacharjee Bhupesh Kumar Mishra 《Molecular physics》2017,115(8):962-970
Dual level of quantum mechanical calculations have been carried out for hydrogen abstraction from Piperazine [HN(CH2CH2)2NH] initiated by OH radical. Geometry optimisation and frequency calculations of all species involved in the titled reaction have been performed at M06-2X/6-31+G(d,p) level of theory. For the accuracy in the thermochemistry and kinetics data, single-point energy calculations have been further carried out at coupled cluster CCSD(T) method along with 6-311G(d,p) basis set. An energy profile diagram for the reaction has been plotted along with pre-reactive and post-reactive complexes at entrance and exit channels. Intrinsic reaction coordinates (IRCs) calculations have been performed for identification of real transition states that connect it via reactant to product. Our result shows that the H-atom abstraction takes place from the C–H position of Piperazine. The rate constant is calculated using canonical transition state theory (CTST) is found to be 2.86 × 10?10 cm3 molecule?1 s?1 which is in good agreement with the reported experimental rate constant (2.38 ± 0.28) × 10?10 cm3 molecule?1 s?1 at 298 K. We have also reported rate constant for the temperature range 300–500 K. Using group-balance isodesmic reaction, the standard enthalpies of formation for Piperazine and product radicals generated by hydrogen abstraction are reported. The branching ratios for both reaction channel (i.e. H-abstraction from –CH2 and –NH position of Piperazine) are found to be 93% and 7%, respectively. The calculated atmospheric life time of Piperazine is found to be 0.97 hour. 相似文献
11.
Uta Wille 《Journal of Physical Organic Chemistry》2011,24(8):672-681
Computational methods were used to gain detailed insight into the mechanism of self‐terminating radical cyclizations, which are initiated by intermolecular addition of O‐centred radicals XO? to alkynes. The calculations were performed for the reaction of NO, SO, and AcO? with cyclodecyne ( 1 ) and 5‐cyclodecynone ( 2 ), respectively. Whereas radical addition and the subsequent transannular radical translocation steps are energetically highly favourable processes for the various XO?, the terminating homolytic β‐fragmentation of the O? X bond in the intermediate α‐oxy radicals 10 – 13 shows a strong dependence on the nature of X. Using simplified model systems, the fragmentation was explored in detail, which revealed that the rate of this step is primarily determined by the strength of the O? X bond and only to a minor extent by the ability of the X moiety to stabilize an unpaired electron in the transition state. However, the cleavage is exothermic, when the released radical X? is resonance stabilized, e.g. NO, SO, and Bn?, respectively. In those cases where the unimolecular β‐fragmentation of the O? X bond is slow, termination could also proceed through a bimolecular radical chain process involving the α‐oxy radical intermediate 10 – 13 and the precursor of XO?, e.g. the Barton PTOC ester 18 or Kim's dithiocarbamate 20 , respectively. Alternative termination mechanisms via oxidation of 10 – 13 can be ruled out under the usual experimental conditions of self‐terminating radical cyclizations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
Mahboob Mohammad Asma Rauf Saba Rauf Muhammad Tariq 《Journal of Physical Organic Chemistry》2012,25(12):1269-1274
To explore the possibility of hydrogen bonding of a stable anion radical with DNA – component sugar, hormones, steroid, and so on (through hydroxyl group), as a first step, the possibility of hydrogen bonding of 1,3‐dinitrobenzene anion radical (1,3‐DNB??) with aliphatic alcohols was studied. It was found that 1,3‐DNB?? anion radical undergoes hydrogen bonding with alcohols: methanol, ethanol, and 2‐proponal. The hydrogen‐bonding equilibrium constant Keq and the (hydrogen‐bonding) rate constants k2 were evaluated through the use of linear scan and cyclic voltammetry theory and techniques. The Keq was found to be in the range of 1.4–6.0 m ?1, whereas the rate constants k2 were found to be in the range of 1.5–3.6 m ?1 s?1, depending upon the hydrogen‐bonding agent and the equation used for the calculation of the rate constants. The hydrogen‐bonding number n was found to be around 0.5 or 1.0. The implication of this study in, for example, the replication of DNA, the prevention of the formation of super oxide, and so on is discussed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
13.
P. Gaikwad G. H. Naik K. I. Priyadarsini B. S. M. Rao 《Journal of Physical Organic Chemistry》2011,24(8):657-662
The reactions of NO and Br radicals with 5‐hydroxyindole (HIn), 5‐hydroxytryptophol (HTpl), 5‐hydroxytryptophan (HTpn) and 5‐hydroxytryptamine (HTpe) were studied using pulse radiolysis. The rate constants for their reaction with NO radical were found to vary from 105 to 107 dm3 mol?1 s?1 in the pH range 5–9 but a higher value (k = 1.4 ± 0.01 × 108 dm3 mol?1 s?1) was noticed in HTpe at pH 9. The gradual increase in reactivity with pH is due to the decrease in the reduction potentials of indoloxyl radicals with E = 0.55 V at pH 9. In contrast, the rate constants with Br radical were found to be diffusion controlled and remained unaffected by the pH. The transient spectra measured are attributed to the indoloxyl radical formed on oxidation with λmax at 420 nm. The indoloxyl radicals further react with the parent hydroxy indole derivative forming the radical adduct and their decay was found to be pH dependent in derivatives containing an amino group. At pH 5, no decay of the radical adducts was seen in all derivatives up to 5 ms whereas those with the amino group decayed faster at pH 9. The total yields of the oxygen centred and carbon centred radicals formed in the reaction of NO radical with hydroxy indoles were found to be nearly equal to G(NO). Our results suggest that NO radical is inefficient in oxidizing hydroxy indoles under physiological conditions preventing the formation of toxic dimers of indole derivatives. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
14.
Jacques Lalevée Nicolas Blanchard Anne‐Caroline Chany Mohamad‐Ali Tehfe Xavier Allonas Jean‐Pierre Fouassier 《Journal of Physical Organic Chemistry》2009,22(10):986-993
The effect of Lewis base coordination on boryl radical reactivity (L→BH where L is triethylamine, 2‐picoline, 4‐dimethylaminopyridine, quinoline and diphenyl phosphine) is examined. Direct detection of the different boryl radicals, their transient absorption spectra, their interaction with double or triple bonds, oxygen, oxidizing agent, alkyl halides and their hydrogen lability have been studied using laser flash photolysis (LFP), kinetic ESR (KESR), ESR spin trapping and MO calculations. For example, a strong decrease of both the bond dissociation energy (BDE)(B? H) (33.8 kcal mol?1) and the addition rate constant to MA (1300 105 to >105 M?1 s?1) was noted when going from the triethylamine borane to the quinoline borane complex, in line with the spin delocalization (1.04 vs. 0.19). These structures are also proposed as new highly efficient co‐initiators for the acrylate photopolymerization. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
15.
Rate constant measurements for initial addition reactions of radicals at the propagation step of photo‐polymerization as studied by pulsed EPR spectroscopy
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Yusuke Miyake Yutaka Marushima Hirona Takahashi Nobuyuki Akai Kazuhiko Shibuya Akio Kawai 《Journal of Physical Organic Chemistry》2016,29(9):468-475
Pulsed EPR spectroscopy was employed to determine reaction rate constants at an early stage of addition reactions in radical polymerizations triggered by four initiator radicals, which were generated by photodissociation of four parent molecules. Two monomers (tert‐butylacrylate and tert‐butylmethacrylate) were examined as reactant. Stern–Volmer analysis on the measured decay time of electron spin echo intensity of reacting radicals provides rate constants for addition reactions. We focused on rate constants for the second step reaction between monomer and adduct radical that is produced by the first step addition reaction between initiator radical and monomer. The rate constant measured by pulsed EPR was evaluated by theoretical calculations in the light of (1) enthalpy difference between product radical and reactants and (2) charge transfer interaction between reacting radical and monomer. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
16.
Basem Kanawati Dieter Lenoir Philippe Schmitt‐Kopplin 《Journal of Physical Organic Chemistry》2011,24(2):83-91
The reaction channels of di‐tert‐butylcarbene ( 2 ), its radical anion, ( 3 ) and its radical cation ( 4 ) were investigated theoretically by using DFT/B3LYP with 6‐31+G(d) basis set and 6‐311+G(2d,p) for single point energy calculations. Conversion of the neutral carbene 2 to the charged species 3 and 4 results in significant geometric changes. In cation 4 two different types of C? (CH3)3 bonds are observed: one elongated sigma bond called “axial” with 1.61 Å and two normal sigma bonds with a bond length of 1.55 Å. Species 2 and 4 have an electron deficient carbon center; therefore, migration of CH3 and H is observed from adjacent tert‐butyl groups with low activation energies in the range of 6–9 kcal/mol like similar Wagner–Meerwein rearrangements in the neopentyl‐cation system. Neutral carbene 2 shows C? H insertion to give a cyclopropane derivative with an activation energy of 6.1 kcal/mol in agreement with former calculations. Contrary to species 2 and 4 , the radical anion 3 has an electron rich carbon center which results in much higher calculated activation energies of 26.3 and 42.1 kcal/mol for H and CH3 migrations, respectively. NBO charge distribution indicates that the hydrogen migrates as a proton. The central issue of this work is the question: how can tetra‐tert‐butylethylene ( 1 ) be prepared from reaction of either species 2 , 3 , or 4 as precursors? The ion–ion reaction between 3 and 4 to give alkene 1 with a calculated reaction enthalpy of 203.5 kcal/mol is extremely exothermic. This high energy decomposes alkene 1 after its formation into two molecules of carbene 2 spontaneously. Ion–molecule reaction of radical anion 3 with the neutral carbene 2 is a much better choice: via a proper oriented charge–transfer complex the radical anion of tetra‐tert‐butylethylene (11) is formed. The electron affinity of 1 was calculated to be negligible. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
17.
18.
Hydrodynamic cavitation (HC) and Fe(II) are advanced oxidation processes, in which pentachlorophenol (PCP) is treated by the redox method of activating persulfate (PS). The kinetics and mechanism of the HC and Fe(II) activation of PS were examined in aqueous solution using an electron spin resonance (ESR) spin trapping technique and radical trapping with pure compounds. The optimum ratio of Fe(II)/PS was 1:2, and the hydroxyl radical (HO) and sulfate radical (SO4−) generation rate were 5.56 mM h−1 and 8.62 μM h−1, respectively. The generation rate and Rct of HO and SO4− at pH 3 and 50 °C in the Fe(II)/PS/HC system are 7584.6 μM h−1, 0.013 and 24.02 μM h−1, 3.95, respectively. The number of radicals was reduced as the pH increased, and it increased with increasing temperature. The PCP reaction rate constants was 4.39 × 10−2 min−1 at pH 3 and 50 °C. The activation energy was 10.68 kJ mol−1. In addition, the mechanism of PCP treatment in the Fe(II)/PS/HC system was a redox reaction, and the HO−/SO4− contribution was 81.1 and 18.9%, respectively. In this study, we first examined PCP oxidation through HO and SO4− quantification using only the Fe(II)/PS/HC process. Furthermore, the results provide the foundation for activation of PS by HC and Fe(II), but also provide a data basis for similar organic treatments other than PCP. 相似文献
19.
Pradnya Nalawade Sergej Naumov Sudhir Kapoor 《Journal of Physical Organic Chemistry》2013,26(11):870-878
The bimolecular electron transfer from p‐amino benzhydrazide (PABH) and its meta‐derivative (m‐amino benzhydrazide (MABH)) to specific one‐electron oxidant results in the formation of anilino radical. In case of PABH, reaction with ?OH radicals results in the synchronous formation of adduct as well as anilino radical. The interesting observation is that the yield of the anilino radical increases with increase in pH. The effect of substitution also has a significant effect on the formation of adduct. In case of MABH, significant yield of anilino radical gets form on reaction with ?OH radical. The free radical electron transfer from PABH and MABH to parent radical cation of non‐polar solvent also results in the formation of anilino radical only suggesting that the radical cation of PABH and MABH has short life time. The above results were supported by quantum chemical calculations. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
20.
Olga B. Morozova Robert Kaptein Renad Z. Sagdeev Alexandra V. Yurkovskaya 《Applied magnetic resonance》2013,44(1-2):233-245
Pulsed-field-gradient nuclear magnetic resonance (NMR) combined with time-resolved chemically induced dynamic nuclear polarization (TR-CIDNP) was applied to study the reduction of guanosyl radicals in reactions with the proteins hen egg white lysozyme (HEWL) and bovine α-lactalbumin (BLA) in their native state. Guanosyl radicals were generated photochemically in the reaction of guanosine-5′-monophosphate with photosensitizer, triplet-excited 2,2′-dipyridyl. In this reaction, at pH 5 guanosyl cation radical is formed, which deprotonates to yield the neutral guanosyl radical. To minimize the contribution of the cation radical, phosphate buffer was added, which accelerates the deprotonation of guanosyl cation radical. From model simulations of CIDNP kinetics the rate constants of the reduction were found to be (3.1 ± 0.5) × 107 M?1s?1 for HEWL and (1.6 ± 0.4) × 107 M?1s?1 for BLA. Also, experiments were carried out at the conditions for denatured HEWL, i.e., at 50 °C in the presence of 10 M urea-d4. The rate constant of the reduction of guanosyl radical in this case was (3.6 ± 0.5) × 108 M?1s?1. 相似文献