共查询到20条相似文献,搜索用时 31 毫秒
1.
在6-311+G(2d,2p)水平下, 采用密度泛函理论(DFT)的B3LYP方法, 研究了Criegee 自由基CH2O2与H2O的反应. 结果表明反应存在三个通道: CH2O2+H2O®HOCH2OOH (R1); CH2O2+H2O®HCO+OH+H2O (R2); CH2O2+H2O®HCHO+H2O2 (R3), 各通道的势垒高度分别为43.35, 85.30和125.85 kJ/mol. 298 K下主反应通道(R1)的经典过渡态理论(TST)与变分过渡态理论(CVT)的速率常数kTST与kCVT均为2.47×10-17 cm3•molecule-1•s-1, 而经小曲率隧道效应模型(SCT)校正后的速率常数kCVT/SCT为 5.22×10-17 cm3•molecule-1•s-1. 另外, 还给出了200~2000 K 温度范围内拟合得到的速率常数随温度变化的三参数Arrhenius方程. 相似文献
2.
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
3.
Hui Zhang Gui-ling Zhang Jing-yao Liu Miao Sun Bo Liu Ze-sheng Li 《Theoretical chemistry accounts》2008,119(5-6):445-451
Theoretical investigations are carried out on the reaction multi-channel CH3COCH3 + Cl (R1) and CH3 COCH3 + CH3 (R2) by means of direct dynamics methods. The minimum energy path (MEP) is obtained at the MP2/6-31 + G(d,p) level, and energetic
information is further refined at the BMC–CCSD (single-point) level. The rate constants are calculated by the improved canonical
variational transition state theory (ICVT) with the small-curvature tunneling (SCT) correction in a wide temperature range
200–3,000 K. The theoretical overall rate constants are in good agreement with the available experimental data and are found
to be k
1 = 3.08 × 10−17
T
2.03exp(−32.96/T) and k
2 = 1.61 × 10−23
T
3.53 exp(−3969.51/T) cm3molecule−1s−1.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Theoretical studies on the reactions of hydroxyl radicals with trimethylsilane and tetramethylsilane
Hui Zhang Gui-Ling Zhang Ying Wang Xiao-Yang Yu Bo Liu Jing-Yao Liu Ze-Sheng Li 《Theoretical chemistry accounts》2008,119(4):319-327
The multiple-channel reactions OH + SiH(CH3)3 → products (R1) and the single-channel reaction OH + Si(CH3)4 → Si(CH3)3CH2 + H2O (R2) have been studied by means of the direct dynamics method at the BMC-CCSD//MP2/6-311+G(2d,2p) level. The optimized geometries,
frequencies and minimum energy path are all obtained at the MP2/6-311+G(2d,2p) levels, and energy information is further refined
by the BMC-CCSD (single-point) level. The rate constants for every reaction channels are calculated by canonical variational
transition states theory (CVT) with small-curvature tunneling (SCT) contributions over the temperature range 200–2,000 K.
The theoretical total rate constants are in good agreement with the available experimental data, and the three-parameter expression
k
1 = 2.53×10−21
T
3.14 exp(1, 352.86/T), k
2 = 6.00 × 10−19
T
2.54 exp(−106.11/T) (in unit of cm3 molecule−1 s−1) over the temperature range 200–2,000 K are given. Our calculations indicate that at the low temperature range, for reaction
R1, H-abstraction is favored for the SiH group, while the abstraction from the CH3 group is a minor channel.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
5.
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
6.
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
7.
The rate constant of the reaction between iodomethane and chlorine atoms at 323 K, measured by the resonance florescence method
under jet stream conditions as the iodine atom yield, is k
1I = (2.9±0.6) × 10−12 cm3 molecule−1 s−1. It is demonstrated experimentally that this reaction takes place mainly on the reactor wall. 相似文献
8.
Hui Zhang Gui-ling Zhang Jing-yao Liu Miao Sun Bo Liu Ze-sheng Li 《Theoretical chemistry accounts》2011,128(3):317-325
Theoretical investigations are carried out on the multichannel reactions CH3COCH3 + F (R1) and CH3COCH3 + Br (R2) by means of direct dynamics methods. The minimum energy path (MEP) is obtained at the MP2/6-31 + G(d,p) level,
and energetic information is further refined at the MC-QCISD (single-point) level. The rate constants are calculated by the
improved canonical variational transition-state theory (ICVT) with the small-curvature tunneling (SCT) contributions in a
wide temperature range 200–1,500 K for the title reactions, H-abstraction channel is favored for the two reactions. The theoretical
overall rate constants are in good agreement with the available experimental data and are found to be k
1a
= 3.22 × 10−15 T
1.51exp(1,190.91/T) cm3 molecule−1 s−1, k
2
= 5.95 × 10−18 T
1.98exp(−4,622.45/T) cm3 molecule−1 s−1. Furthermore, the rate constants of reaction Cl + CH3COCH3 (R3) calculated in the other paper are added to discuss the reactivity trend of different halogen reaction with acetone on
the rate constants of this class of hydrogen abstraction reactions. 相似文献
9.
Yuan Zhang Hui Zhang Jing-Yao Liu Xue-Mei Duan Ze-Sheng Li 《Theoretical chemistry accounts》2011,130(1):115-125
Theoretical studies are carried out on the multi-channel reactions of SiH(CH3)3 with Cl (reaction 1, R1) and Br atoms (R2) by direct dynamics method. The minimum energy path is calculated at the MP2/6-31+G(d,p)
level, and energetic information is further refined by the MC-QCISD (single-point) method. The rate constants for individual
reaction channels, R1a, R1b-in, R1b-out, R1c, R1d, R2a, R2b-in, R2b-out, R2c, and R2d, are calculated by the improved canonical
variational transition state theory with small-curvature tunneling correction over the temperature range 200–1,500 K. The
theoretical three-parameter expressions k
1
(T) = 6.30 × 10−15
T
1.36exp(704.94/T) and k
2
(T) = 9.41 × 10−26
T
4.89exp(−1,033.80/T) cm3 molecule−1 s−1 are given. Our calculations indicate that reaction channels R1c and R2c are the major channel. 相似文献
10.
The reaction mechanisms for ozonolysis of ethyl vinyl ether (EVE) and propyl vinyl ether (PVE) have been investigated using
the density functional theory (DFT) and ab initio method. Cycloaddition reactions of O3 to EVE and PVE are highly exothermic by 52.91 and 53.17 kcal/mol, respectively. Major products (formaldehyde, ethyl formate,
and propyl formate) resulting from the both reactions are identified by comparing them with the experimental results. Further
reactions of the most energy-rich Criegee intermediates (C2H5OCHOO and C3H7OCHOO) have been proposed in the presence of NO and H2O in which the main products are ethyl formate and propyl formate. The Multichannel Rice–Ramsperger–Kassel–Marcus (RRKM) approach
is employed to calculate the total and individual rate constants for major product channels over a wide range of temperatures
and different pressures. In the temperature range of 200–2500 K, the main path is the production of ethyl formate with k
EVE+O3 = 4.67 × 10−12 exp(−3029/T), for the EVE with O3 reaction and k
PVE+O3 = 3.58 × 10−12 exp(−2858/T) for the PVE with O3 reaction. At 298 K and 760 torr, the rate constants calculated are 1.80 × 10−16 and 2.45 × 10−16 cm3 molecule−1 s−1 for ozonolysis of EVE and PVE, which are consistent with the experimental results. The total rate constants show positive
temperature dependence over the temperature range of 200–2000 K but pressure independence in the range of 0.01–10000 Torr.
Estimation of branching ratios of several products is also performed. The influence of carbon chain length on reactivity toward
ozone is examined. 相似文献
11.
Homopolymerization of methyl methacrylate (MMA) was carried out in the presence of triphenylstibonium 1,2,3,4-tetraphenyl-cyclopentadienylide
as an initiator in dioxane at 65°C±0·l°C. The system follows non-ideal radical kinetics (R
p
∝ [M]1·4 [I]0·44
@#@) due to primary radical termination as well as degradative chain-transfer reaction. The overall activation energy and average
value ofk
2
p
/k
t
were 64 kJmol−1 and 0.173 × 10−3 1 mol−1 s−1 respectively 相似文献
12.
I. K. Larin N. A. Messineva A. I. Spasskii E. M. Trofimova L. E. Turkin 《Kinetics and Catalysis》2000,41(4):437-443
The reactions of iodine monoxide (IO•) with sulfur-containing compounds, which are important for the atmospheric chemistry, are studied. An attempt is made to
distinguish between the heterogeneous and homogeneous reaction pathways. It is shown that, under the experimental conditions,
the reactions proceed on the wall and generate iodine atoms into the gas phase. It is found that, at room temperature, the
rate constants for the gas-phase reactions of IO• with (CH3)2S and H2S are lower than 2.5 × 10−14 and 8.0 × 10−14 cm3 molecule−1 s−1, respectively; the rate constant for the gas-phase reaction of iodine monoxide with SO2 ≤ 5.6 × 10−15 cm3 molecule−1 s−1. 相似文献
13.
The effects of a substrate additive, H+ and solvents (water and acetone), on the micelle-catalyzed aquation of tris-(4,7-diphenyl-1, 10-phenanthroline)iron(II),
Fe(Ph2Phen)3
2+, have been investigated using#Triton X-100 micelles. The k0
vs. [TX-100] profiles at fixed [H2O] are structured, exhibiting maxima. Catalytic factors of 46.6–171.7 are observed for 5.56×10−2≤[H2O] 55.60×10−2 mol dm−3. On the other hand, at fixed [H+], the k0
vs. [TX-100] exhibit broad maxima. The aquation reaction is inhibited by H+ and catalytic factors decrease rapidly and exponentially from 422.5 to 20.9 for 0.20×10−3≤[H+]≤2.00×10−3 mol dm−3. The aquation is found to be faster (ca. 160–1200 fold) in acetone than in the aqueous medium depending on the added [H2O]. These observations are rationalized on the basis of a proposed modified lamellar structure for the Triton X-100 (TX-100)
micelles in which direct substitution of water molecules into the coordination sphere of the complex occurs. 相似文献
14.
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
15.
《Journal of Chemical Sciences》1991,103(3):499-503
A laser flash photolysis/resonance fluorescence investigation has been carried out to study the kinetics of the overall reactions
OH + cyclopropane (1) and OH + cyclobutane (2) in the temperature range 298–490 K and at 298 K, respectively. The following
kinetic parameters have been determined: k1 =(3.9 ±0.6) 10−12exp- (2.2 ± 0.1)kcal mol−1/RT molecule−1cm3s−1, k2(298 K) = (17.5 ± 1.5)10−13molecule−1 cm3s−1. 相似文献
16.
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
17.
A. I. Kazakov Yu. I. Rubtsov G. B. Manelis L. P. Andrienko 《Russian Chemical Bulletin》1997,46(12):2015-2020
Kinetic regularities of thermal decomposition of dinitramide in aqueous and sulfuric acid solutions were studied in a wide
temperature range. The rate of the thermal decomposition of dinitramide was established to be determined by the rates of decomposition
of different forms of dinitramide as the acidity of the medium increases: first, N(NO2)− anions, then HN(NO2)2 molecules, and finally, protonated H2N(NO2)2
+ cations. The temperature dependences of the rate constants of the decomposition of N(NO2)− (k
an) and HN(NO2)2 (k′ac) and the equilibrium constant of dissociation of HN(NO2)2 (K
a) were determined:k
an=1.7·1017 exp(−20.5·103/T), s−1,k′ac=7.9·1016 exp(−16.1·103/T), s−1, andK
a=1.4·10 exp(−2.6·103/T). The temperature dependences of the decomposition rate constant of H2N(NO2)2
+ (k
d) and the equilibrium constant of the dissociation of H2N(NO2)2
+ (K
d) were estimated:k
d=1012 exp(−7.9·103/T), s−1 andK
d=1.1 exp(6.4·103/T). The kinetic and thermodynamic constants obtained make it possible to calculate the decomposition rate of dinitramide solutions
in a wide range of temperatures and acidities of the medium.
In this series of articles, we report the results of studies of the thermal decomposition of dinitramide performed in 1974–1978
and not published previously.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2129–2133, December, 1997. 相似文献
18.
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
19.
A high‐resolution IR diode laser in conjunction with a Herriot multiple reflection flow‐cell has been used to directly determine the rate coefficients for simple alkanes with Cl atoms at room temperature (298 K). The following results were obtained: k(Cl + n‐butane) = (1.91 ± 0.10) × 10?10 cm3 molecule?1 s?1, k(Cl + n‐pentane) = (2.46 ± 0.12) × 10?10 cm3 molecule?1 s?1, k(Cl + iso‐pentane) = (1.94 ± 0.10) × 10?10 cm3 molecule?1 s?1, k(Cl + neopentane) = (1.01 ± 0.05) × 10?10 cm3 molecule?1 s?1, k(Cl + n‐hexane) = (3.44 ± 0.17) × 10?10 cm3 molecule?1 s?1 where the error limits are ±1σ. These values have been used in conjunction with our own previous measurements on Cl + ethane and literature values on Cl + propane and Cl + iso‐butane to generate a structure activity relationship (SAR) for Cl atom abstraction reactions based on direct measurements. The resulting best fit parameters are kp = (2.61 ± 0.12) × 10?11 cm3 molecule?1 s?1, ks = (8.40 ± 0.60) × 10?11 cm3 molecule?1 s?1, kt = (5.90 ± 0.30) × 10?11 cm3 molecule?1 s?1, with f( ? CH2? ) = f (? CH2? ) = f (?C?) = f = 0.85 ± 0.06. Tests were carried out to investigate the potential interference from production of excited state HCl(v = 1) in the Cl + alkane reactions. There is some evidence for HCl(v = 1) production in the reaction of Cl with shape n‐hexane. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 34: 86–94, 2002 相似文献
20.
The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L2, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that
the electrode reaction of Cu(II)L2 is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA,
the formation of the electrochemically non-active complexes Cu(II)L2-DNA, results in the decrease of the peak current of Cu(II)L2. Based on the electrochemical behavior of the Cu(II)L2 with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under
the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range
from 3 × 10−8 to 3 × 10−6 g · mL−1 for calf thymus DNA, from 1.6 × 10−8 to 9.0 × 10−7 g · mL−1 for fish sperm DNA, and from 3.3 × 10−8 to 5.5 × 10−7 g · mL−1 for yeast RNA. The detection limits are 3.3 × 10−9, 6.7 × 10−9 and 8.0 × 10−9 g · mL−1, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples. 相似文献