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1.
Gergely Kovács ákos Bencsura Sándor Dóbé Tibor Bérces Ferenc Márta 《Reaction Kinetics and Catalysis Letters》2005,86(2):355-361
Summary Pulsed laser photolysis coupled with time-resolved UV-absorption monitoring of CH3CO•radicals was applied to obtain the rate constant, k1, for the reaction CH3CO•+ HBr → CH3C(O)H + Br (1); k1(298 K) = (3.59 ± 0.23 (2σ))x10-12cm3molecule-1s-1. Utilization of k1in a third law procedure has provided the standard enthalpy of formation value ofDfH°298(CH3CO•) = -10.04 ± 1.10 (2σ) kJ mol-1in excellent agreement with a very recent IUPAC recommendation. 相似文献
2.
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
3.
Gergely Kovács Tas Szász-Vadász Vassilis C. Papadimitriou Sándor Dóbé Tibor Bérces Ferenc Márta 《Reaction Kinetics and Catalysis Letters》2005,87(1):129-138
Summary Pulsed laser photolysis with resonance fluorescence monitoring of OH radicals was applied at T = 300±2 K to obtain the rate constants of k1= (3.38±0.60)x10-12, k2= (2.52±0.44)x10-13and k3 = (1.06±0.30)x10-13cm3molecule-1s-1with 2σprecision given for the overall reactions OH + CH3CH2OH (1), OH + CF2HCH2OH (2) and OH + CF3CH2OH (3), respectively. k2is the first direct kinetic data for the reaction of OH radicals with CF2HCH2OH reported in the literature.</o:p> 相似文献
4.
The mechanism and kinetics of the production of hydroxymethyl hydroperoxide (HMHP) in ethene/ ozone/water gas-phase system were investigated at room temperature (298±2 K) and atmospheric pressure (1×105 Pa). The reactants were monitored in situ by long path FTIR spectroscopy. Peroxides were measured by an HPLC post-column fluorescence technique after sampling with a cold trap. The rate constants (k3) of reaction CH2O2 H2O→HMHP (R3) determined by fitting model calculations to ex-perimental data range from (1.6―6.0)×10?17 cm3·molecule?1·s?1. Moreover, a theoretical study of reac-tion (R3) was performed using density functional theory at QCISD(T)/6-311 (2d,2p)//B3LYP/6-311 G(2d, 2p) level of theory. Based on the calculation of the reaction potential energy surface and intrinsic reac-tion coordinates, the classic transitional state theory (TST) derived k3 (kTST), canonical variational tran-sition state theory (CVT) derived k3 (kCVT), and the corrected kCVT with small-curvature tunneling (kCVT/SCT) were calculated using Polyrate Version 8.02 program to be 2.47×10-17, 2.47×10-17 and 5.22×10-17 cm3·molecule-1·s-1, respectively, generally in agreement with those fitted by the model. 相似文献
5.
Emese Szabó Jérémy Tarmoul Alexandre Tomas Christa Fittschen Sándor Dóbé Patrice Coddeville 《Reaction Kinetics and Catalysis Letters》2009,96(2):299-309
Kinetics of the •OH-initiated reactions of acetic acid and its deuterated isomers have been investigated performing simulation chamber experiments
at T = 300 ± 2 K. The following rate constant values have been obtained (± 1σ, in cm3 molecule−1 s−1): k
1(CH3C(O)OH + •OH) = (6.3 ± 0.9) × 10−13, k
2(CH3C(O)OD + •OH) = (1.5 ± 0.3) × 10−13, k
3(CD3C(O)OH + •OH) = (6.3 ± 0.9) × 10−13, and k
4(CD3C(O)OD + •OH) = (0.90 ± 0.1) × 10−13. This study presents the first data on k
2(CH3C(O)OD + •OH). Glyoxylic acid has been detected among the products confirming the fate of the •CH2C(O)OH radical as suggested by recent theoretical studies. 相似文献
6.
The rate constants of the reactions of the chlorine atom with C3F7I (k
1) and CF3I (k
2) have been measured using the resonance fluorescence of chlorine atoms in a flow reactor at 295 K: k
1 = (5.2 ± 0.3) × 10−12 cm3 molecule−1 s−1 and k
2 = (7.4 ± 0.6) × 10−13 cm3 molecule−1 s−1. No iodine atoms have been detected in the reaction products. 相似文献
7.
Roger Atkinson Janet Arey Sara M. Aschmann Stephanie B. Corchnoy Yonghui Shu 《国际化学动力学杂志》1995,27(10):941-955
Rate constants for the gas-phase reactions of the four oxygenated biogenic organic compounds cis-3-hexen-1-ol, cis-3-hexenylacetate, trans-2-hexenal, and linalool with OH radicals, NO3 radicals, and O3 have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm3 molecule?1 s?1 units): cis-3-hexen-1-ol: (1.08 ± 0.22) × 10?10 for reaction with the OH radical; (2.72 ± 0.83) × 10?13 for reaction with the NO3 radical; and (6.4 ± 1.7) × 10?17 for reaction with O3; cis-3-hexenylacetate: (7.84 ± 1.64) × 10?11 for reaction with the OH radical; (2.46 ± 0.75) × 10?13 for reaction with the NO3 radical; and (5.4 ± 1.4) × 10?17 for reaction with O3; trans-2-hexenal: (4.41 ± 0.94) × 10?11 for reaction with the OH radical; (1.21 ± 0.44) × 10?14 for reaction with the NO3 radical; and (2.0 ± 1.0) × 10?18 for reaction with O3; and linalool: (1.59 ± 0.40) × 10?10 for reaction with the OH radical; (1.12 ± 0.40) × 10?11 for reaction with the NO3 radical; and (4.3 ± 1.6) × 10?16 for reaction with O3. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals, and O3 results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc. 相似文献
8.
Edit Farkas Gergely Kovács Krisztina Imrik István Szilágyi Sándor Dóbé Ferenc Márta 《Reaction Kinetics and Catalysis Letters》2004,83(2):315-320
The discharge flow method with laser induced fluorescence detection of CH3O was applied to determine the rate constant, k
1, for the reaction CH3O + HBr → products (1) k
1 (298 K) = (8.41 ± 0.80(1σ)) 1011 cm3 mol-1 s-1. The unusually large k
1 value was explained by the polar nature of the transition state of the reaction.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
9.
Jonathan F. Ojo Jide Ige Grace O. Ogunlusi Olanrewaju Owoyomi Esan S. Olaseni 《Transition Metal Chemistry》2006,31(6):782-785
The kinetics of the reactions between Fe(phen)
3
2+
[phen = tris–(1,10) phenanthroline] and
Co(CN)5X3− (X = Cl, Br or I) have been investigated in aqueous acidic solutions at I = 0.1 mol dm−3 (NaCl/HCl). The reactions were carried out at a fixed acid concentration ([H+] = 0.01 mol dm−3) and the second-order rate constants for the reactions at 25 °C were within the range of (0.151–1.117) dm3 mol−1 s−1. Ion-pair constants K
ip for these reactions, taking into consideration the protonation of the cobalt complexes, were 5.19 × 104, 3.00 × 102 and 4.02 × 104 mol−1 dm−3 for X = Cl, Br and I, respectively. Activation parameters measured for these systems were as follows: ΔH* (kJ K−1 mol−1) = 94.3 ± 0.6, 97.3 ± 1.0 and 109.1 ± 0.4; ΔS* (J K−1) = 69.1 ± 1.9, 74.9 ± 3.2 and 112.3 ± 1.3; ΔG* (kJ) = 73.7 ± 0.6, 75.0 ± 1.0 and 75.7 ± 0.4; E
a
(kJ) = 96.9 ± 0.3, 99.8 ± 0.4, and 122.9 ± 0.3; A (dm3 mol−1 s−1) = (7.079 ± 0.035) × 1016, (1.413 ± 0.011) × 1017, and (9.772 ± 0.027) × 1020 for X = Cl, Br, and I respectively. An outer – sphere mechanism is proposed for all the reactions. 相似文献
10.
Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that
the reactions have two product channels: NH2+ HNCO?NH3+NCO (1) and NH2+HNCO?N2H3+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48
kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance
with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300–2700 K, transition theory rate constant
for reaction (1) is 1.68×1011–3.29×1011 mL·mol-1·s-1, which is close to the experimental one of 5.0×1011mL·mol-1·s-1or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes,cis andtrans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (forcis-mode) and 147.43 kJ/mol (fortrans-mode), respectively, which is much higher than reaction (1). So reaction (1) is the main channel for the titled reaction. 相似文献
11.
Günter Grampp Stephan Landgraf Tomasz Wesierski Beata Jankowska Ewa Kalisz Dana-Maria Sabou Boryana Mladenova 《Monatshefte für Chemie / Chemical Monthly》2002,212(4):1363-1372
The kinetics of the CrO(O2)2 formation by H2O2 and Cr2O7
2− in aqueous acidic media was measured at 293 ± 2 K in a pH range between 2.5 and 3.3. Using the stopped-flow method with rapid scan UV-VIS detection, the rate law of the formation
of CrO(O2)2 was determined. For the media HClO4, HNO3 and CH3COOH, the reaction order in the Cr2O7
2− concentration was found to be 0.5. For [H2O2] as well as for [H+], the reaction was first order in all acids used. In HCl and H2SO4 media the reaction was first order in Cr2O7
2−. At T = 293 ± 2 K the rate constant for the formation of Cr(O)(O2)2 was found to be (7.3 ± 1.9) · 102 M−3/2 s−1 in HClO4. 相似文献
12.
Gabriella Poggi Mila D’Angelantonio Marialuisa Russo Salvatore S. Emmi 《Research on Chemical Intermediates》2008,34(1):1-20
The oxidation process of the cyclic acetal sorbitylfurfural (SF) has been thoroughly examined from the kinetic, spectroscopic
and theoretical point of view. Oxidation has been initiated by the radiolitically produced OH radical in the presence of variable
oxygen amounts. Two competing reaction pathways are evidenced which lead to quite different products, although they do not
affect the acetal ring integrity. The peroxidation of the hydroxylated furanic ring (k
4=(6.1±0.9)×108 M−1 s−1) maintains the ring structurevia HO2• elimination (k
6=(1.9±0.4)×105 s−1). Unlike that, the peroxidation of the pseudo-allylic radical (k
5=(1.9±0.9)×109 M−1 s−1), formedvia β-cleavage, fixes the destructured intermediate, leading to a tetroxide, which slowly decomposes through a Russell mechanism
(k
8=(2.3±0.6)×102 s−1). It is confirmed that the steady state concentration of the tetroxide is very low, which suggests a molar absorption coefficient
for it around 1.2×104 M−1 cm−1 at 265 nm. The end products of the latter pathway have been characterized as carboxylic and butenald-sorbitol derivatives. The kinetic and spectral data of every step of the process have been fitted by the above outlined mechanism.
The energetics of the mechanism has been detailed byab initio computations as well, carrying further substantiation to it. Semi-empirical calculations were also employed to describe the
spectral properties of each intermediate. 相似文献
13.
Edit Farkas István Szilágyi Sándor Dóbé Tibor Bérces Ferenc Márta 《Reaction Kinetics and Catalysis Letters》2003,80(2):351-358
The discharge-flow method with resonance fluorescence detection of OH radicals was applied to obtain the rate constant value
of k
D = 1.95 ± 0.14 (1σ) 1010 cm3 mol-1s-1 at 298 K. Combination with k
H from our previous study gives the kinetic isotope effect of k
H / k
D = 5.33 ± 0.41. OH + CH3C(O)CH3 → Products (H) OH + CD3C(O)CD3 → Products(D)
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
14.
The following reaction rate constants of oxygen atoms with iodomethane and chlorine were measured using resonance fluorescence
under jet conditions at 298 K: k
1 = (2.4 ± 0.5) × 10–15 and k
2 = (6.9 ± 0.2) × 10−14 cm3/s, respectively. 相似文献
15.
The kinetics of the oxidation of cyclopentanone with decaneperoxysulfonic acid at 291–323 K in CCl4 has been studied. The reaction is not autocatalytic, and its rate increases linearly with increases in the concentrations
of each of the reagents. The addition of CF3COOH does not affect the reaction rate. The observed results are explained within a scheme which is a special case of the
well-known Baeyer-Villiger reaction mechanism established for peroxycarboxylic acids. The effective rate constant of the process
has been determined: logk (L mol−1 s−1)=(7.6±1.7) — (42.1±9.6)/θ, where θ=2.30RT kJ mol−1.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1827–1829, October, 1993. 相似文献
16.
V. V. Konovalova V. V. Fomichev D. V. Drobot R. M. Zakalyukin S. Yu. Stefanovich 《Russian Journal of Inorganic Chemistry》2009,54(10):1650-1654
The conducting phase Li6ZnNb4O14 in the Li2O-ZnO-Nb2O5 system has been obtained by solid-phase synthesis from Li3NbO4, Li1 − x
NbO3, and LiZnNbO4. The new phase exists in the temperature range of (904 ± 5)–(1145 ± 5)°C. Quenching the synthesis product from 960°C yields
this phase in a metastable state at room temperature. The Li6ZnNb4O14 phase has been characterized by thermal analysis, chemical analysis, and X-ray powder diffraction. The ohmic resistance of
ceramic Li6ZnNb4O14 has been determined by complex impedance measurements. The activation energy of conduction, derived from the temperature
dependence of conductivity, is E
a = 0.273 ± 0.001 eV. The conductivity of the phase at 300°C is 1.2 × 10−2 S cm−1. 相似文献
17.
G. Xie S. P. Chen S. L. Gao X. X. Meng Q. Z. Shi 《Journal of Thermal Analysis and Calorimetry》2006,83(3):693-700
A novel solid complex, formulated as Ho(PDC)3
(o-phen), has been obtained from the reaction
of hydrate holmium chloride, ammonium pyrrolidinedithiocarbamate (APDC) and
1,10-phenanthroline (o-phen·H2O)
in absolute ethanol, which was characterized by elemental analysis, TG-DTG
and IR spectrum. The enthalpy change of the reaction of complex formation
from a solution of the reagents, ΔrHmθ (sol), and the molar heat capacity of the complex, cm,
were determined as being –19.161±0.051 kJ mol–1
and 79.264±1.218 J mol–1 K–1
at 298.15 K by using an RD-496 III heat conduction microcalorimeter. The enthalpy
change of complex formation from the reaction of the reagents in the solid
phase, ΔrHmθ(s), was calculated as
being (23.981±0.339) kJ mol–1 on the
basis of an appropriate thermochemical cycle and other auxiliary thermodynamic
data. The thermodynamics of reaction of formation of the complex was investigated
by the reaction in solution at the temperature range of 292.15–301.15
K. The constant-volume combustion energy of the complex, ΔcU, was determined as being –16788.46±7.74
kJ mol–1 by an RBC-II type rotating-bomb
calorimeter at 298.15 K. Its standard enthalpy of combustion, ΔcHmθ, and standard enthalpy of formation,
ΔfHmθ, were calculated to be –16803.95±7.74 and –1115.42±8.94
kJ mol–1, respectively. 相似文献
18.
P. C. Schulz M. A. Morini M. E. Gschaider de Ferreira 《Colloid and polymer science》1998,276(3):232-238
The system dodecyltrimethylammonium hydroxide (DTAOH)–water was studied by surface tension, ion-selective electrodes and
evaporation in an electrobalance. Results confirmed earlier conclusions about a stepwise aggregation mechanism in DTAOH solutions.
The aggregation process started at a total concentration C
T=(2.51±0.10)×10-4 mol dm-3) which probably corresponds to the formation of dimers. At C
T= (1.300±0.041)×10-3 mol dm-3 there was a change in the surface and evaporation behavior, corresponding to the formation of small, fully ionized aggregates
which grew with increasing concentration. At C
T= (1.108±0.010)×10-2 mol dm-3 the formation of true micelles with hydroxide counterions in the Stern layer did not change significantly the evaporation
and adsorption behavior. This means that between this concentration and C
T=(3.02±0.28)× M28.8n10-2 mol dm-3, the changes in structure were gradual. At the latter concentration there was a sudden change in the monolayer state at the
air/water interface, with a strong surfactant desorption, and a major change in evaporation behavior. The changes are compatible
with the formation of few, large aggregates reducing the total concentration of kinetically independent solute units, which
in turn increased the activity of the solvent. This phenomenon is in agreement with literature information. The reduction
in the evaporation rate of water was mainly due to the reduction of the water activity, caused by colligative effects. The
reduction of the effective area available for evaporation had only a slight effect in water evaporation.
Received: 9 January 1997 Accepted: 19 October 1997 相似文献
19.
Dechlorination of Ru(PPh3)2(TaiMe)Cl2 (TaiMe = p-Me-C6H4-N=N-C3H2NN(1)-Me (1), 1-methyl-2-(p-tolylazo)imidazole) has been carried out in acetone solution by Ag+ and reacted with N,N’-chelators to synthesise [Ru(PPh3)2 (TaiMe)(N,N’)]2+. The complexes have been isolated as their perchlorate salts. The N,N’ chelators are 1-alkyl-2-(phenylazo)imidazoles (PaiX,
X = Me, Et, CH2Ph); 2-(arylazo)pyridines, (Raap,p-R-C6H4-N=N-C5H4N; R = H, Me, Cl); 2-(arylazo)pyrimidines (Raapm,p-R-C6H4-N=N-C3N2H2; R = H, Me, Cl); 2,2’-bipyridine (bpy) and 1,10-phenanthroline (o-phen). Unsymmetrical N,N’ chelators may give two isomers
and this is indeed observed. The1H NMR spectral data refer to the presence of two isomers in the mixture in different proportions. With consideration of coordination
pairs in the order of PPh3, PPh3; N,N (N refers to N(immidazole)) and N’,N (N’ refers to N(azo)), the complexes have been characterised astrans-cis-cis andtrans-trans-trans configuration; the former predominates in the mixture. Electrochemical studies exhibit high potential Ru(III)/Ru(II) couple
and quasireversible N=N reduction. Electronic spectra show high intensity (ε ∼ 104) MLCT transition in the visible region (520 ±10) nm along with a shoulder (ε ∼ 103) in the longer wavelength region. 相似文献
20.
Comparative method to evaluate reliable kinetic triplets of thermal decomposition reactions 总被引:1,自引:0,他引:1
Reliable kinetic information for thermal analysis kinetic triplets can be determined by the comparative method: (1) An iterative
procedure or the KAS method had been established to obtain the reliable value of activation energy E
a of a reaction. (2) A combined method including Coats-Redfern integral equation and Achar differential equation was put forward
to confirm the most probable mechanism of the reaction and calculate the pre-exponential factor A. By applying the comparative
method above, the thermal analysis kinetic triplets of the dehydration of CaC2O4·H2O were determined, which apparent activation energy: 81±3 kJ mol-1, pre-exponential factor: 4.51·106-1.78·108 s-1, the most probable mechanism function: f(α)=1 or g(α)=α, which the kinetic equation of dehydration is dα/dt=Ae-E
a
/RT.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献