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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.
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
3.
Janina A. Rosso Sonia G. Bertolotti Andr M. Braun Daniel O. Mrtire Mnica C. Gonzalez 《Journal of Physical Organic Chemistry》2001,14(5):300-309
We report mechanistic studies on the reactivity of CO2 . − radicals towards substituted benzenes, XPh, with X = NO2, COOH, COH, CH3, H, Cl and HO. Vacuum ultraviolet (VUV, 172 nm) irradiation of aqueous solutions containing formate was used as a method of CO2 . − radical generation for the study of the reaction products, which were determined by gas chromatography–mass spectrometry and high‐performance liquid chromatography. The nature of some of the reaction intermediates was studied by laser flash photolysis of aqueous solutions of peroxodisulfate in the presence of formate. The observed products and intermediates of reaction are discussed and rationalized by a dual reactivity of the CO2 . − radical anion with substituted benzenes: a one‐electron reduction and radical addition to the aromatic ring. For substituted benzenes with X = NO2, COOH and COH, the observed products support an electron transfer from CO2 . − to the substrates as the primary reaction channel, while the reactions with toluene follow the channel of radical addition. Benzene and chlorobenzene react with CO2 . − by both routes, electron transfer and radical addition. Our experimental results indicate that H abstraction by the CO2 . − radical is negligible under the chosen experimental conditions. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
4.
V. G. Maslov 《Journal of Applied Spectroscopy》1995,62(2):225-228
“S. I. Vavilov State Optical Institute”, All-Russia State Scientific Center, 12, Birzhevaya Liniya, St. Petersburg, 199034,
Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 2, pp. 52–56, March–April, 1995 相似文献
5.
《Journal of Electrostatics》2014,72(5):412-416
Many studies have been reported for contact electrification based on the electron transfer from donors to acceptors. However, the chemical structures of donors and acceptors have not been identified. Here we calculated the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy levels of model structures of mechano anions, mechano cations and mechano radicals which were produced by the heterogeneous and homogeneous scissions of covalent bonds comprising polymer main chain in vacuum at 77 K. We identified the donors are mechano anions(HOMO) and mechano radicals(HOMO), and the acceptors are mechano cations(LUMO) and mechano radicals(LUMO). The contact electrification is due to the electron transfer from the donors to the acceptors during contacting on the friction surface, and produces mosaic nano-scopic domains with opposite sign. The sign of the net charge of polymer was deduced from the number of paths of electron acceptance reaction. The relative sign of charge and position on the triboelectric series were deduced from their chemical structure. 相似文献
6.
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
7.
用Na2O2-DMSO体系产生O2·的ESR研究 总被引：6，自引：0，他引：6
提出了Na2O2的二甲基亚砜(DMsO)/H2O溶液中产生超氧阴离子自由基(O2·)的新方法,用电子自旋共振仪(ESR)可直接检测到很强的O2·信号,研究了反应的条件及其O2·信号的特性,并用该法考察了茶多酚等清除剂对于超氧阴离子自由基的清除作用。结果表明本体系是产生O2·的有效方法,可用于超氧阴离子自由基清除剂的研究。 相似文献
8.
Till Biskup 《Molecular physics》2013,111(24):3698-3703
Electron transfer plays a key role in many biological systems, including core complexes of photosynthesis and respiration. As this involves unpaired electron spins, electron paramagnetic resonance (EPR) is the method of choice to investigate such processes. Systems that show photo-induced charge separation and electron transfer are of particular interest, as here the processes can easily be synchronised to the experiment and therefore followed directly over its time course. One particular class of proteins, the cryptochromes, showing charge separation and in turn spin-correlated radical pairs upon excitation with blue light, have been investigated by time-resolved EPR spectroscopy in great detail and the results obtained so far are summarised in this contribution. Highlights include the first observation of spin-correlated radical pairs in these proteins, a fact with great impact on the proposed role as key part of a magnetic compass of migratory birds, as well as the assignment of the radical-pair partners and the unravelling of alternative and unexpected electron transfer pathways in these proteins, giving new insights into aspects of biological electron transfer itself. 相似文献
9.
Ryoichi Akaba Masaki Kamata Akiko Koike Ken-Ichi Mogi Yasunao Kuriyama Hirochika Sakuragi 《Journal of Physical Organic Chemistry》1997,10(11):861-869
Photoinduced electron transfer reactions of trans-stilbene sensitized by 2,4,6-triphenylthiapyrylium tetrafluoroborate (STPP) were carried out by steady-state and laser flash photolysis techniques in the presence and absence of oxygen in dichloromethane. Rapid dimerization of the trans-stilbene cation radical with its neutral species was observed, as previously observed in 2,4,6-triphenylpyrylium tetrafluoroborate (TPP)-sensitized reactions in dichloromethane. Electrochemical and photophysical properties such as fluorescence quantum yield and T–T absorption spectrum of STPP were also studied, and the results were compared with those for TPP. The properties of STPP as an electron transfer sensitizer are discussed. © 1997 John Wiley & Sons, Ltd. 相似文献
10.
Long-Min Wu Jian-Ming Lü Xiao-Lin Wen Xue-Qing Jia You-Cheng Liu Zhong-Li Liu 《Journal of Physical Organic Chemistry》1997,10(3):152-158
An appreciable equilibrium isotope effect has been observed for electron transfer from phenothiazine (PT) to the radical cation of its 15N-substituted analogue ([15N]PT+·), i.e. PT+[15N]PT+· ⇋ K PT+·+[15N]PT via electron paramagnetic resonance analysis of the mixed radical cations formed from mixing the [15N]phenothiazine radical cation hexachloroantimonate and phenothiazine in acetonitrile (K=0·77±0·10 at 25 °C), and by physical separation of the neutral phenothiazines from the radical cation salts in the equilibrium mixture (K=0·83±0·10 at 25 °C). Infrared and Raman spectra of [14N]- and [15N]phenothiazines and their radical cations were measured to assign the vibrational frequency shifts caused by the heavy-atom substitution and radical cation formation, which gave an estimate of the enthalpy change of 441·7 J mol−1 for the electron transfer process. These results reveal that 15N substitution of phenothiazine decreases appreciably the ionization potential of the molecule, making it easier to lose an electron to form the corresponding radical cation in solution. © 1997 by John Wiley & Sons, Ltd. 相似文献
11.
甲基紫精与醇类间的光诱导电子转移及光催化反应的ESR研究 总被引：1，自引：0，他引：1
用ESR方法研究了甲基紫精(MV++)与甲醇,乙醇及苄醇等之间的光诱导电子转移和光反应过程.结果发现,甲基紫精存在条件下,某些很稳定的醇类也可以发生光催化分解和光催化氧化的反应,甲基紫精在反应过程中起的是催化剂的作用在无氧条件下,MV++/C2H5OH体系经UV光照10min后即可观察到很强的MV+离子基的信号,表明甲基紫精与乙醇分子之间发生了电子转移;当进行较长时间光辐照,则MV+离子基逐步消失而生成H原子和碳中心自由基。在通氧条件下进行光照时,则无MV+基信号而产生OOH基和碳中心自由基的信号.当体系中有一定量的水存在时,OOH基减弱而产生·OH基,且随着水量的增加,·OOH基的强度更为减弱直至消失,而同时羟基浓度则大大增加.另一个有趣而重要的现象是,对于MV++/苄醇体系,在通氧条件下辐照时可给出很强的超氧阴离子基O2-的信号,而MV++/甲醇体系可产生较弱的O2-信号.但是在无氧时甲基紫精的存在进行光辐照甲醇并不发生反应,而苄醇却可被甲基紫精光催化分解产生很强的苄氧基,羟甲基等自由基.本文详细地研究和讨论了甲基紫精与几种醇之间的光诱导电子转移和相应的均相光催化反应过程的机理. 相似文献
12.
In the reactions of ozone with organic compounds in aqueous solution, O is an abundant intermediate. A basic aspect of its conversion into •OH is addressed here. The reactions O•− + O2 ⇄ O (1), H+ + O•− ⇄ •OH (8), •OH + O2 ⇄ HO (6), and H+ + O ⇄ HO (5) are interconnected by a thermodynamic cycle. For equilibria (1) and (8) reliable equilibrium constants, and hence Gibbs energies are available (ΔG0(1) = −32 kJ mol−1, ΔG0(8) = 67 kJ mol−1). For reaction (6), a Gibbs energy of ΔG0(6) = 47 kJ mol−1 (K6 = 10−8.2 M) has now been calculated by G1. From the thermodynamic cycle one hence arrives at ΔG0(5) = −12 kJ mol−1. This relates to pKa(HO) = −2.1. Thus, the HO radical is a very strong acid. This value agrees with a value of −2.0 obtained from the Bielski and Schwarz relationship for pKa values of OxHy compounds. Reaction (6) must be very slow, 0.1 < k6 < 104 M−1 s−1. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
13.
本文在无氧条件下利用ESR分别观察了肝脏和晶状体的微粒体及线粒体酶在NADPH存在下还原三硝基甲苯(TNT)的过程,检测到参数为g=2.0048±0.0005,A对位N=1.215mT,A对位N=0.800±0.010mT,AH=0.122±0.0206mT的自由基信号,并通过电子计算机对ESR谱的模拟证明该自由基信号为TNT硝基阴离子自由基,根据其超精细分裂常数认为,其不配对电子的电子云密度主要分布在对位硝基上。 相似文献
14.
15.
Ting‐Wei Mu Lei Liu Xiao‐Song Li Qing‐Xiang Guo 《Journal of Physical Organic Chemistry》2001,14(8):559-565
PM3 and B3LYP/3‐21G(d) calculations were performed on the inclusion complexation of cyclodextrins (CD) with radical ions. The calculations reproduced the experimental observations that the complexation of α‐CD with 1,4‐dicyanobenzene was weaker than with its radical anion, and that the complexation of β‐CD with phenothiazine was weaker than with its radical cation. On the other hand, calculations showed that the complexation of α‐CD with p‐nitrophenolate was stronger than with its radical anion and the complexation of β‐CD with viologen was stronger than with its radical cation. The different magnitudes of the interactions between the charged species and CD or water were proposed to cause such behaviors. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
16.
A. Alberti M. Benaglia B. F. Bonini M. Fochi D. Macciantelli M. Marcaccio F. Paolucci S. Roffia 《Journal of Physical Organic Chemistry》2004,17(12):1084-1090
ESR studies carried out during the reaction of ferrocenoylsilanes with Grignard reagents at low temperature led to the detection of the radical anions of the former compounds. Cyclic voltammetric experiments indicate that the observed radical anions are likely to originate through an inner‐sphere electron transfer process. Different radical species were observed upon annealing, originating from destruction of the ferrocenyl moiety. Paramagnetic species were also detected on reacting ferrocenoylsilanes with LiAlH4. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
17.
Benzaldehyde in THF reacts with lithium metal to give the expected reduction product, benzyl alcohol, plus benzoin and benzyl as minor products. The kinetics of the overall reaction as well as the partial rate coefficients of the several steps have been determined under various reaction conditions. It was found that adsorption on the surface and electron transfer from the lithium to benzaldehyde are the slow steps. The experimental results show interesting surface effects, and evidence for significant radical intermediates, which were characterized by their epr spectra and trapping experiments, results useful to gain insight into the mechanisms of these and other related reactions. © 1997 John Wiley & Sons, Ltd. 相似文献
18.
《Ultrasonics sonochemistry》2014,21(5):1875-1880
Perfluorooctanoic acid (PFOA) is a recalcitrant organic pollutant in wastewater because of its wide range of applications. Technologies for PFOA treatment have recently been developed. In this study, PFOA decomposition by sonochemical treatment was investigated to determine the effects of NaHCO3 concentrations, N2 saturation, and pH on decomposition rates and defluorination efficiencies. The results showed that PFOA decomposition by ultrasound treatment only (150 W, 40 kHz), with or without saturated N2, was <25% after 4 h reaction. The extent and rate of PFOA decomposition and defluorination efficiencies of PFOA, however, greatly increased with the addition of carbonate radical reagents. PFOA was completely decomposed after 4 h of sonochemical treatment with a carbonate radical oxidant and saturated N2. Without saturated N2, PFOA was also decomposed to a high (98.81%) degree. The highest PFOA decomposition and defluorination efficiencies occurred in N2 saturated solution containing an initial NaHCO3 concentration of 30 mM. Sonodecomposition of PFOA with CO3− radical was most favorable in a slightly alkaline environment (pH = 8.65). There isn’t any shorter-chain perfluorinated carboxylic acids detected except fluorine ions in final reaction solution. 相似文献
19.
动力学分光光度法测定中药对超氧阴离子自由基的清除率 总被引：10，自引：3，他引：7
建立了一种利用动力学分光光度法测定中药对超氧阴离子自由基清除率的新方法。研究表明：当波长为520 nm、黄嘌呤氧化酶浓度为4×10-3 μg·mL-1,反应时间在2～7 min时,可得到最佳测定条件。在该条件下测得的抗坏血酸对超氧阴离子自由基的清除率与文献报道值一致。方法用于中药厚朴和杜仲的测定,它们对超氧阴离子自由基的IC50分别为7.580和323.800 mg·L-1。 相似文献
20.
Most organic bond-forming reactions can be described as nucleophile–electrophile combinations. For many of these reactions there have been discussions as to whether the bond formation occurs together with the electron transfer or whether electron transfer and bond formation take place in separate steps. This discussion is reviewed and it is shown how to distinguish between the different processes based on kinetic analysis. © 1997 by John Wiley & Sons, Ltd. 相似文献