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1.
The reaction of the · OH radical with the oxalate ion in an acidic aqueous solution was studied by pulse radiolysis. The rate
constant for the reaction of formation of the radical HOOC-COO·(λmax = 250 nm, ɛ = 1800 L mol−1 cm−1) is (5.0±0.5)·107 L mol−1 s−1. In the reaction with the hydrogen ion (k = 1.1·107 L mol−1 s−1), the radical HOOC-COO· is transformed into a nonidentified radical designated arbitrarily as H+(HOOC-COO)· (λmax = 260 nm, ɛ = 4000 L mol−1 cm−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1165–1167, June, 2008. 相似文献
2.
D. Yu. Vorobyev V. F. Plyusnin Yu. V. Ivanov V. P. Grivin S. V. Larionov H. Lemmetyinen 《Russian Chemical Bulletin》2005,54(10):2364-2373
The nature of intermediate species and their reactions were studied by laser pulse photolysis for a photochromic system consisting
of 8,8′-diquinolyl disulfide (RSSR) and a planar NiII complex di(mercaptoquinolinato)nickel(II) (Ni(SR)2) in toluene and benzene solutions. Under exposure to laser radiation, disulfide RSSR dissociates to two RS· radicals, whose spectrum has an intense absorption band with a maximum at λ = 400 nm (ε = 8400 L mol−1 cm−1). The radicals disappear by recombination (2k
rec = 4.6 · 109 L mol−1 s−1). In the presence of the Ni(SR)2 complex, coordination of the radical (k
coord = 4.4 · 109 L mol−1 s−1) competes with recombination to form a radical complex RS· Ni(SR)2 having an intense absorption band with a maximum at 460 nm (ε = 16 600 L mol−1 cm−1). This species decays in the second-order reaction (2k = 4.6 · 104 L mol−1 s−1). Since the photochromic system returns to the initial state, the reaction of two radical complexes is assumed to produce
radical recombination and reduction of the disulfide and Ni(SR)2 complex. Analysis of the kinetic data showed that some RS· radicals decay in the microsecond time interval due to the reaction with the RS· Ni(SR)2 radical complex (k = 3.1 · 109 L mol−1 s−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2291–2300, October, 2005. 相似文献
3.
At near neutral pH (approx. 5.5), the OH-adduct of chlorogenic acid (CGA), formed on pulse radiolysis of N2O-saturated aqueous CGA solutions (λ
max = 400 and 450 nm) with k = 9 × 109 dm3 mol−1 s−1, rapidly eliminates water (k = 1 × 103 s−1) to give a resonance-stabilized phenoxyl type of radical. Oxygen rapidly adds to the OH-adduct of CGA (pH 5.5) to form a
peroxyl type of radical (k = 6 × 107 dm3 mol−1 s−1). At pH 10.5, where both the hydroxyl groups of CGA are deprotonated, the rate of reaction of · OH radicals with CGA was
essentially the same as at pH 5.5, although there was a marked shift in the absorption maximum to approx. 500 nm. The CGA
phenoxyl radical formed with more specific one-electron oxidants, viz., Br
2
·−
and N
3
·
radicals show an absorption maximum at 385 and 500 nm, k ranging from 1–5.5 × 109 dm3 mol−1 s−1. Reactions of other one-electron oxidants, viz., NO
2
·
, NO· and CCl3OO· radicals, are also discussed. Repair rates of thymidine, cytidine and guanosine radicals generated pulse radiolytically at
pH 9.5 by CGA are in the range of (0.7–3) × 109 dm3 mol−1 s−1. 相似文献
4.
The radiation chemical redox transformations in solutions of bromides in the presence of minor additives of iodides were studied
by pulse radiolysis. The change in the concentrations of the Br− and I− ions changes the ratio of the formed short-lived radical anions Br2
·−, BrI·−, and I2
·−. The spectrum of the mixed radical anion BrI·− contains a broad optical band at 370 nm with ɛ370 = 9650 L mol−1 cm−1. The reduction potential of the BrI·−/Br−, I− pair is 1.25 V. The rate constants for the forward and backward reactions Br2
·− + I− ⇌ BrI·− + Br− are k
f = 4.3·109 and k
r = 1.0·105 L mol−1 s−1, respectively; for the reactions BrI·− ⇌ Br− + I·, k
f = 5.7·108 s−1 and k
r = 1.0·1010 L mol−1 s−1.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1787–1792, September, 2008. 相似文献
5.
The phenyl substituted acridine-1,8-dione (AD) dye reacts with (CH3)2*COH radicals with a bimolecular rate constant of 0.6 × 108 dm3 mol−1 s−1 in acidic aqueous-organic mixed solvent system. The transient optical absorption band (λmax = 465 nm, ɛ = 6.8 × 102 dm3 mol−1 cm−1) is assigned to ADH* formed on protonation of the radical anion. In basic solutions, (CH3)2*COH radicals react with a bimolecular rate constant of 4.6 × 108 dm3 mol−1 s−1 and the transient optical absorption band (λmax = 490 nm, ɛ = 10.4 × 103 dm3 mol−1 cm−1) is assigned to radical anion, AD*−, which has a pKa value of 8.0. The reduction potential value of the AD/AD*− couple is estimated to be between −0.99 and −1.15 V vs NHE by pulse radiolysis studies. The cyclic voltammetric studies showed
the peak potential close to −1.2 V vs Ag/AgCl. 相似文献
6.
K. B. Petrushenko I. K. Petrushenko V. I. Smirnov N. V. Zorina E. Yu. Shmidt 《Russian Chemical Bulletin》2010,59(4):779-783
The electronic absorption spectra of radical cations of dipyrroles with a phenylene bridge were studied by laser flash photolysis
and quantum chemical methods. Intense absorption bands of the radical cations in the visible region (λmax ≈ 500 nm, εmax > 2 · 104 L mol−1 cm−1) are caused by excitation of electrons from single occupied MOs to the LUMO. In the near IR region, calculations predict
additional, relatively intense (f≈ 0.27–0.29) electronic transitions associated with excitation of electrons from low-lying MOs to the single occupied MO. 相似文献
7.
The ultraviolet-visible absorption spectrum of C60(OH)18 in water showed an absorption band with λmax = 215 nm and other characteristic absorption bands of C60 are not observed. The singlet-singlet and triplet-triplet absorption bands are not observed in the 400–900 nm region. It
has low reactivity with eaq− and formed an absorption band with λmax = 580 nm. The hydroxyl radicals react with a bimolecular rate constant of 2.4×109 dm3 mol−1 s−1 and showed an absorption band at 540 nm. 相似文献
8.
Pulse radiolysis of resveratrol was carried out in aqueous solutions at pH ranging from 6.5 to 10.5. The one-electron oxidized
species formed by the N•3 radicals at pH 6.5 and 10.5 were essentially the same with λmax at 420 nm and rate constant varying marginally (k = (5−6.5) × 109 dm3 mol−1 s−1). The nature of the transients formed by NO•2, NO• radical reaction at pH 10.5 was the same as that with N•3, due to the similarity in decay rates and the absorption maximum. Reaction of •OH radical with resveratrol at pH 7 gives an absorption maximum at 380 nm, attributed to the formation of carbon centered
radical. The repair rates for the thymidine and guanosine radicals by resveratrol were approx. 1 × 109 dm3 mol−1 s−1, while the repair rate for tryptophan was lower by nearly an order of magnitude (k = 2 × 108 dm3 mol−1 s−1). The superoxide radical anion was scavenged by resveratrol, as well as by the Cu–resveratrol complex with k = 2 × 107 and 1.5 × 109 dm3 mol−1 s−1, respectively. Its reduction potential was also measured by cyclic voltammetry. 相似文献
9.
Hari Mohan 《Journal of Chemical Sciences》2002,114(6):749-758
In neutral aqueous solution of (phenylthio)acetic acid, hydroxyl radical is observed to react with a bimolecular rate constant
of 7.2 × 10-1 dm3 mol−s− and the transient absorption bands are assigned to•OH radical addition to benzene and sulphur with a rough estimated values of 50 and 40% respectively. The reaction of the•OH radical with diphenyl sulphide (k = 4.3 × 108 dm3 mol−1 s−1) is observed to take place with formation of solute radical cation, OH-adduct at sulphur and benzene with estimated values
of about 12, 28 and 60% respectively. The transient absorption bands observed on reaction of•OH radical, in neutral aqueous solution of 4-(methylthio)phenyl acetic acid, are assigned to solute radical cation (λmax = 550 and 730 nm), OH-adduct at sulphur (λmax = 360 nm) and addition at benzene ring (λmax = 320 nm). The fraction of•OH radical reacting to form solute radical cation is observed to depend on the electron-withdrawing power of substituted group.
In acidic solutions, depending on the concentration of acid and electron-withdrawing power, solute radical cation is the only
transient species formed on reaction of•OH radical with the sulphides studied. 相似文献
10.
A. M. Nazarov E. M. Chainikova S. L. Khursan A. N. Ryzhkov R. L. Safiullin V. D. Komissarov 《Russian Chemical Bulletin》1998,47(7):1292-1295
The kinetics of self-termination of benzophenone oxide (BPO) in the liquid phase was studied by flash photolysis. The extinction
coefficient of BPO (ε) was found to be virtually independent of the solvent nature, ε=(1.9±0.1)·103 L mol−1 cm−1. The rate constant of the BPO self-temination increases from 1.8·107 (MeCN) and 7.4·107 (C6H6) to 1.5·109 (n-decane) and 2.0·109 L mol−1 s−1 (n-pentane) at 293±2 K. Solvation of BPO promotes a polar state of the molecule in MeCN and C6H6. In nonpolar hydrocarbons, a great contribution is made by the biradical structure resulting in an increase in the rate constant
and a shift of the absorption maximum to the long-wave region (from 410 nm in MeCN to 425 nm inn-pentane). In solutions of benzene and acetonitrile, benzophenone oxide reacts with the parent diazo compound with a rate
constant of (2–4)·105 L mol−1 s−1 (293±2 K) along with the self-termination.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1329–1332, July, 1998. 相似文献
11.
Reactions of e−aq, OH radicals and H atoms were studied with n-allylthiourea (NATU) using pulse radiolysis. Hydrated electrons reacted with
NATU (k = 2.8×109 dm3 mol−1 s−1) giving a transient species which did not have any significant absorption above 300 nm. It was found to transfer electrons
to methyl viologen. At pH 6.8, the reduction potential of NATU has been determined to be −0.527 V versus NHE. At pH 6.8, OH radicals were found to react with NATU, giving a transient species having absorption maxima at 400–410
nm and continuously increasing absorption below 290 nm. Absorption at 400–410 nm was found to increase with parent concentration,
from which the equilibrium constant for dimer radical cation formation has been estimated to be 4.9×103 dm3 mol−1. H atoms were found to react with NATU with a rate constant of 5 × 109 dm3 mol−1 s−1, giving a transient species having an absorption maximum at 310 nm, which has been assigned to H-atom addition to the double
bond in the allyl group. Acetoneketyl radicals reacted with NATU at acidic pH values and the species formed underwent reaction
with parent NATU molecule. Reaction of Cl.−2 radicals (k = 4.6 × 109 dm3 mol−1 s−1) at pH 1 was found to give a transient species with λmax at 400 nm. At the same pH, reaction of OH radicals also gave transient species, having a similar spectrum, but the yield
was lower. This showed that OH radicals react with NATU by two mechanisms, viz., one-electron oxidation, as well as addition to the allylic double bond. From the absorbance values at 410 nm, it has been
estimated that around 38% of the OH radicals abstract H atoms and the remaining 62% of the OH radicals add to the allylic
double bond. 相似文献
12.
V. A. Nadtochenko N. N. Denisov V. Yu. Gak N. V. Abramova N. M. Loim 《Russian Chemical Bulletin》1999,48(10):1900-1903
It was found that the quantum yield of the fluorescence ofmeso-tetraferrocenylporphyrin (TFcP) is at most 3.0·10−5, and that of the triplet state of FTcP is at least 200 times lower than the quantum yield ofmeso-tetraphenylporphyrin (TPP). Excitation of TFcP in CCl4 by light with λ>410 nm results in the oxidation of TFcP. The singlet and triplet excited states of TPP in toluene and acetonitrile
are quenched by ferrocene with rate constants of 1.2·1010 and 1.7·1010, (4.6±0.5)·108 and (1.37±0.21)·109 L mol−1 s−1, respectively. The quenching mechanisms are discussed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1924–1927, October, 1999. 相似文献
13.
P. Manoj H. Mohan V. M. Manoj J. P. Mittal C. T. Aravindakumar 《Research on Chemical Intermediates》2006,32(9):817-826
Pulse radiolysis has been used to investigate the reaction of hydroxyl radical (·OH) and oxide radical anion (O·−) with 2-aminopurine (2AP), a fluorescent analogue of adenine, in aqueous medium. The second-order rate constant for the reaction
of ·OH with 2AP was determined to be 3 × 109 dm3 mol−1s−1 and for the reaction of O·− it was 7.1 × 108 dm3 mol−1s−1. The transient absorption spectrum obtained in the reaction of ·OH at pH 7 has absorption maxima at 370 and 470 nm. The spectrum undergoes a time-dependent transformation at higher time-scale.
The intermediate species was found to react with N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD). The yield of TMPD·+ was calculated in terms of G(TMPD·+) to be 3.3 × 10−7 mol J−1 at pH 7. The ·OH reactions were also carried out at pH 10 and the transient absorption spectra have λ
max at 400 and 480 nm. The transient spectra obtained in the reaction of O·− at pH ≈14 have maxima at 400 and 480 nm. The transient intermediate species at pH 7 are assigned to the formation of 2AP-4-OH· (54%), 2AP-5-OH· (7%) and 2AP-8-OH· (39%) based on the spectral evidence and TMPD·+ build-up. Both 2AP-4-OH· and 2AP-5-OH· undergo OH− elimination to form a radical cation. At higher pH (pH 10), the dehydration reaction of these OH-adducts leads to a N-centered
radical (2AP-N(9)·, 71%). Formation of 2AP-8-OH· (29%) is also proposed at this pH. In the reaction of O·− with 2AP, it is proposed that a similar nitrogen centered 2AP-N(9)· radical is formed by an electron-transfer reaction at N(9). 相似文献
14.
The •OH and the NO2
• radicals generated pulse radiolytically in N2O-saturated aqueous solution at pH 8–8.5 oxidize Mesna to form the corresponding thiyl radicals which on reaction with thiolate
ions form an RSSR•
− type of transient with λmax = 420 nm. The rate constants for the formation of these transients were determined. In the absence of O2 at pH=6, the RS• radicals formed show an absorption maximum at 360 nm and an ε=200±50 dm3 mol−1 cm−1. The rate constant k (•OH+RSH) was 6×109 dm3 mol−1 s−1 as determined from competition kinetics. In the presence of O2 the Mesna thiyl radical was seen to rapidly add oxygen to form an RSOO• type of species with λmax = 535 nm, ε=700±50 dm3 mol−1 cm−1 and k (RS•+O2)=1.3×108 dm3 mol−1 s−1. Both the RS• and the RSOO• radicals formed by the oxidation of Mesna were able to abstract H-atoms from ascorbate ions and k(RS• +AH−)=~k(RSOO•+AH−)=~6−7×108 dm3 mol−1 s−1-. Moderately strong oxidants like CCl3OO• and the (CH3)3CO• radicals, having a reduction potential of +1.4−1.6 V vs NHE were unable to oxidize Mesna. The results thus reflect on the
pro- and anti-oxidant properties of Mesna. 相似文献
15.
The decay kinetics of hydrated electron (eaq
−) formed upon photolysis of aqueous solutions of sodium pyrene-1,3,6,8-tetrasulfonate at λ = 337 nm in the presence of phosphate
anions (up to 2 mol L−1) was studied by nanosecond laser-pulse photolysis in a wide range of pH (3.5–10) and ionic strength (I, up to 2 mol L−1) values. At high pH values, where the HPO4
2− ions dominate, the eaq
− decay kinetics depends only slightly on phosphate concentration (rate constant for the reaction is at most 2·105 L mol−1 s−1). The H2PO4
− ions react with eaq
− at a rate constant of 2.8·106 L mol−1 s−1 (I = 0), which increases linearly with the parameter
in accordance with the Debye-Hückel theory. The rate constant for quenching of eaq
− by H3PO4 at pH ≤ 4 decreases linearly with the parameter
due to the secondary salt effect and equals 1.6·109 L mol−1 s−1 at I = 0. The logarithm of the rate constant for quenching of eaq
− by phosphates is linearly related to the number of the O-H bonds in the phosphate molecule.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1277–1280, July, 2007. 相似文献
16.
17.
K. Pietrucha L. Góra K. Burczak 《Journal of Radioanalytical and Nuclear Chemistry》1998,232(1-2):83-86
Hydroxyl radicals were generated radiolytically in N2O-saturated aqueous solutions of the aminoglycoside antibiotic, gentamycin. Using the pulse radiolysis technique, the rate
constant of OH radicals with gentamycin determined was 1.2·109 dm3·mol−1·s−1. Upon.OH attack a transient species with an absorption maximum at 270 nm is observed which decays by second-order kinetics within
the solute concentration range of 3.2·10−5 to 1·10−3mol·dm−3. Transient species undergoes transformation to a permanent product absorbing between 260 and 340 nm with maximum absorption
at 300 nm. Rate constant of the reaction of bimolecular decay of gentamycin radicals, k (Gen.+Gen.) was found to be ≈ 1.4·107 dm3·mol−1·s−1. 相似文献
18.
Radiation chemical reactions of•OH, O•−, N3
•and e
aq
t-
witho- and m-hydroxycinnamic acids were studied. The second-orderrateconstantsforthereaction of•OH with ortho and meta isomers in buffer solution at pH7 are 3.9±0.2 × 109 and 4.4 ± 0.3 × 109 dm3 mol-1 s-1 respectively. At pH 3 the rate with the ortho isomer was halved (1.6 ± 0.4 × 109 dm3 mol-1 s-1) but it was unaffected in the case of meta isomer (k = 4.2±0.6 × 109dm3mol-1 s-1). The rate constant in the reaction of N3
• with the ortho isomer is lower by an order of magnitude (k = 4.9 ± 0.4 × 108 dm3 mol-1s-1). The rates of the reaction of e
aq
t-
with ortho and meta isomers were found to be diffusion controlled. The transient absorption spectrum measured in the•OH witho-hydroxycinnamic acid exhibited an absorption maximum at 360 nm and in meta isomer the spectrum was blue-shifted (330 nm)
with a shoulder at 390 nm. A peak at 420 nm was observed in the reaction of Obb−with theo-isomer whereas the meta isomer has a maximum at 390 and a broad shoulder at 450 nm. In the reaction of the absorption peaks
were centred at 370–380 nm in both the isomers. The underlying reaction mechanism is discussed. 相似文献
19.
The kinetics of hydroquinone-inhibited oxidation of acrylic acid and methyl methacrylate was studied volumetrically by measuring
the oxygen uptake in the presence of an initiator (azobisisobutyronitrile) at T = 333 K and P
O
2 = 1 and 0.21 atm. The oxidation of acrylic acid inhibited by 4-methoxyphenol was studied under the same conditions for comparison.
The rate constants of the reactions of the peroxyl radicals of acrylic acid (∼CH2CH(COOH)O2·) and methyl methacrylate (∼CH2CMe(COOMe)O2·) with hydroquinone (HOC6H4OH) (1.20 × 105 and 7.16 × 104 l mol−1 s−1, respectively) and of the reaction of peroxyl radicals of acrylic acid with 4-methoxyphenol (p-CH3OC6H4OH) (3.25 × 104 l mol−1 s−1) were measured. The stoichiometric inhibition factors f were determined. The reaction between the semiquinone radical and oxygen, O2 + HOC6H4O·, plays an important role, decreasing the factor f and the efficiency of the inhibition effect of hydroquinone. The rate constants of this reaction were calculated from kinetic
data: k = 5.72 × 102 (in acrylic acid) and 4.60 × 102 l mol−1 s−1 (in methyl methacrylate). 相似文献
20.
V. N. Smirnov 《Kinetics and Catalysis》2011,52(2):166-169
The results of our experimental studies and an analysis of the published data on the rate constant for the reaction Fe + O2 = FeO + O in the forward (I) and reverse (−I) direction are reported. The data obtained in this work are described by the
expressions k
1 = 6.2 × 1014exp(−11100 K/T) cm3 mol−1 s−1 and k
−1 = 6.0 × 1013exp(−588 K/T) cm3 mol−1 s−1 (T = 1500–2500 K). The generalized expressions for the temperature dependences of these rate constants derived by combining
our results with the literature data can be presented as k
1 = 9.4 × 1014(T/1000)0.022exp(−11224 K/T) cm3 mol−1 s−1 (T = 1500–2500 K) and k
−1 = 1.8 × 1014(1000/T)0.37exp(−367 K/T) cm3 mol−1 s−1 (T = 200–2500 K). 相似文献