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1.
Rate constants have been measured in several aqueous/organic solvent mixtures for the addition reaction of Cl2˙? radicals with 2-propen-1-o1 and 2-buten-1-o1 as a function of temperature and with 2, 3-dimethyl-2-butene at room temperature. The rate constants were in the range of 106–109 L mol?1 s?1, the activation energies were relatively low (1–10 kJ mol?1), and the pre-exponential factors varied over the range log A = 7.9 to 9.4. The rate constants (k) decreased (by up to a factor of 30) upon increasing the fraction of organic solvent and log k correlated linearly with the dielectric constant for a given water/organic solvent system, but the lines for the different solvent systems had different slopes. A better correlation of log k was found with a combination of the solvatochromic factor, ET(30), and the hydrogen-bond donor acidity factor, α. This suggests that the rate of reaction is influenced by the solvent polarity and also by specific solvation of the ionic reactant and product. Solvent effect on the reaction of SO4˙? with 2-propen-1-o1 was studied for comparison. © 1993 John Wiley & Sons, Inc.  相似文献   

2.
Rate constants have been measured in aqueous solutions for the reactions of the carbonate radical, CO3˙?, with several saturated alcohols and one cyclic ether as a function of temperature. Arrhenius pre-exponential factors ranged from 2×108 to 1×109 ?? mol?1 s?1 and activation energies ranged from 16 to 29 kJ mol?1. The results suggest that the reactions are not pure hydrogen abstraction, but involve an additional interaction of the radical with the ? OH or ? O? linkage. © 1993 John Wiley & Sons, Inc.  相似文献   

3.
Rate constants have been determined for the reactions of SO4? with a series of alcohols, including hydrated formaldehyde. The SO4? radical was produced by the laser-flash photolysis of persulfate, S2O82?. Rate constants for the reactions of SO4? with alcohols range from 1.0 × 107 for methanol to 3.4 × 108 M?1 s?1 for 1-octanol. Rate constants for the reactions of SO4? with deuterated methanol and ethanol are lower by about a factor of 2.5. For methanol, ethanol, and 2-propanol, the temperature dependence of the rate constant was determined over the range 10–45°C.  相似文献   

4.
Rate constants have been determined for the reactions of SO4? with a series of alkanes and ethers. The SO4? radical was produced by the laser-flash photolysis of persulfate, S2O82?. For methane, only an upper limit of 1 × 106 M?1 s?1 could be determined. For ethane, propane, and 2-methylpropane, rate constants of 0.44, 4.0, and 10.5 × 107 M?1 s?1 were found. For ethyl and n-propyl ether, rate constants of 1.3 × 108 and 2.2 × 108 M?1 s?1 were found and for 1,4-dioxane and tetrahydrofuran, rate constants of 7.2 × 107 and 2.8 × 108 were obtained. The reaction of SO4? with allyl alcohol was also studied and found to have a rate constant of 1.4 × 109 M?1 s?1.  相似文献   

5.
The bimolecular reactions in the title were measured behind shock waves by monitoring the O-atom production in COS? O2? Ar and CS2? O2? Ar mixtures over the temperature range between 1400 and 2200 K. A value of the rate constant for S + O2 → SO + O was evaluated to be (3.8 ± 0.7) × 1012 cm3 mol?1 s?1 between 1900 and 2200 K. This was connected with the data at lower temperatures to give an expression k2 = 1010.85 T0.52 cm3 mol?1 s?1 between 250 and 2200 K. An expression of the rate constant for CS2 + O2 → CS + SO2 was obtained to be k21 = 1012.0 exp(?32 kcal mol?1/RT) cm3 mol?1 s?1 with an error factor of 2 between 1500 and 2100 K.  相似文献   

6.
The λ-Radiolysis reactions of mitomycin C ( 1 ) and its derivatives were studied in the hope of developing a radiation-induced drug (RID). The λ-radiolysis reactions were carried out in aqueous solutions under the condition where hydrated electron (e?aq) was generated as a principal reactive species. The competitive λ-radiolysis studies revealed that the rate constants for the reactions of 1 with e?aq at room temperature was 3.6 × 1010 dm3 mol?1s?1. Among mitomycin C derivatives, the 5H-6-alkoxyimino derivatives 11 and 12 , and compound 13 in which ring A of 1 has the 4-hydroxy-6-hydroxyimino structure cleaved to give 1 . The mechanic aspect of these λ-radiolysis reactions is discussed.  相似文献   

7.
The initiation reaction of the polymerization of α-methylstyrene by trityl tetrachloroferate and tritylhexachloroantimonate in 1,2-dichloroethane at 20°C was studied. The rate constants were 14 × 10?3 and 27 × 10?3 L mol?1s?1, respectively. The dissociation constants of tritylterachloroferate (Kd = 0.88 × 10?4M?1) and tritylhexachloroantimonate (Kd = 2.64 × 10?4M?1) was determined. The effect of electron acceptors and donors on the dissociation equilibrium and initiation rate was investigated. It was shown that in strongly dissociated ion pairs such as stable carbenium salts the electron donors and acceptors have no appreciable effect on the magnitude of the dissociation. The temperature dependence of the rate constants in the ?20–+20°C range yielded the following thermodynamic parameters for trityltetrachloroferate: Ei = 8.54 kcal/mol; A = 3.2 × 104 mol?1s?1; ΔH* = 8 kcal/mol; and S* = ?39.8 eu.  相似文献   

8.
Laser flash photolysis (at 248 or 308 nm) or aryl iodides in water or water/methanol solutions produces iodine atoms and phenyl radicals. Iodine atoms react rapidly with added I? to form I2? but do not react rapidly with O2 (k ? 107 L mol?1 s?1). Iodine atoms oxidize phenols to phenoxyl radicals, with rate constants that vary from 1.6 × 107 L mol?1 s?1 for phenol to about 6 × 109 L mol?1 s?1 for 4-methoxyphenol and hydroquinone. Ascorbate and a Vitamin E analogue are also oxidized very rapidly. N-Methylindole is oxidized by I atoms to its radical cation with a diffusion-controlled rate constant, 1.9 × 1010 L mol?1 s?1. Iodine atoms also oxidize sulfite and ferrocyanide ions rapidly but do not add to double bonds. The phenyl radicals, produced along with the I atoms, react with O2 to give phenylperoxyl radicals, which react with phenols much more slowly than I atoms. © 1995 John Wiley & Sons, Inc.  相似文献   

9.
The rate constant for the Menschutkin reaction of 1,2‐dimethylimidazole with benzyl bromide to produce 3‐benzyl‐1,2‐dimethylimidazolium bromide was determined in a number of ionic liquids and molecular organic solvents. The rate constants in 12 ionic liquids are in the range of (1.0–3.2) × 10?3 L mol?1 s?1 and vary with the solvent anion in the order (CF3SO2)2 N? < PF6? < BF4?. Variations with the solvent cation (butylmethylimidazolium, octylmethylimidazolium, butyldimethylimidazolium, octyldimethylimidazolium, butylmethylpyrrolidinium, and hexyltributylammonium) are minimal. The rate constants in the ionic liquids are comparable to those in polar aprotic molecular solvents (acetonitrile, propylene carbonate) but much higher than those in weakly polar organic solvents and in alcohols. Correlation of the rate constants with the solvatochromic parameter E T(30) is reasonable within each group of similar solvents but very poor when all the solvents are correlated together. Better correlation is obtained for the organic solvents by using a combination of two parameters, π* (dipolarity/polarizibility) and α (hydrogen bond acidity), while additional parameters such as δ (cohesive energy density) do not provide any further improvement. © 2004 Wiley Periodicals, Inc. *
  • 1 This article is a US Government work and, as such, is in the public domain of the United States of America.
  • Int J Chem Kinet 36: 253–258, 2004  相似文献   

    10.
    Rate constants have been measured by pulse radiolysis for the reactions of the NO3 radical with five cyclic ethers and a series of alcohols. Rate constants ranged from 3.5 × 104 M×1 s×1 for deuterated methanol to 1.1 × 107 M?1 s?1 for tetrahydrofuran. The rate constants for the reactions of NO3 with the alcohols 1-propanol to 1-heptanol were found to be linearly dependent on the number of CH3 groups with a group reactivity of 6.4 × 105 M?1 s?1.  相似文献   

    11.
    The gas‐phase elimination kinetics of the above‐mentioned compounds were determined in a static reaction system over the temperature range of 369–450.3°C and pressure range of 29–103.5 Torr. The reactions are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius expressions: ethyl 3‐(piperidin‐1‐yl) propionate, log k1(s?1) = (12.79 ± 0.16) ? (199.7 ± 2.0) kJ mol?1 (2.303 RT)?1; ethyl 1‐methylpiperidine‐3‐carboxylate, log k1(s?1) = (13.07 ± 0.12)–(212.8 ± 1.6) kJ mol?1 (2.303 RT)?1; ethyl piperidine‐3‐carboxylate, log k1(s?1) = (13.12 ± 0.13) ? (210.4 ± 1.7) kJ mol?1 (2.303 RT)?1; and 3‐piperidine carboxylic acid, log k1(s?1) = (14.24 ± 0.17) ? (234.4 ± 2.2) kJ mol?1 (2.303 RT)?1. The first step of decomposition of these esters is the formation of the corresponding carboxylic acids and ethylene through a concerted six‐membered cyclic transition state type of mechanism. The intermediate β‐amino acids decarboxylate as the α‐amino acids but in terms of a semipolar six‐membered cyclic transition state mechanism. © 2005 Wiley Periodicals, Inc. Int J Chem Kinet 38: 106–114, 2006  相似文献   

    12.
    The kinetics and mechanism of the reaction of complexation of iron(III) with 2,4-octanedione and 2,4-nonanedione have been investigated spectrophotometrically in aqueous solution at 10°C and ionic strength 0.5 mol dm?3 NaClO4. The equilibrium constants of the mono-complexes have been determined. The mechanism proposed to account for the kinetic data involves a double reversible pathway where both Fe3+ and Fe(OH)2+ react with the enol tautomer of the ligand. 2,4-Octanedione reacts with Fe3+ and Fe(OH)2+ with rate constants of 0.65 dm3 mol?1 s?1, and 14.07 dm3 mol?1 s?1, respectively. For 2,4-nonanedione complexation the rate constants determined are 0.49 dm3 mol?1 s?1, and 11.39 dm3 mol?1 s?1, respectively. Some discussions are made on the basis of Eigen-Wilkins theory considering the effect of solvent exchange on the complex formation. © 1993 John Wiley & Sons, Inc.  相似文献   

    13.
    The kinetics of the catalyzed dehydration of HCO3? by zinc(II) containing tripod complexes has been studied at 25°C using the stopped‐flow technique. The direction of reaction curve was changed in aqueous solution when the pH of the solution was greater than 7.5. The pH‐profile of rates of the dehydration reactions indicates that only the aqua complex catalyzes the dehydration of HCO3? via a ligand substitution process. The second‐order rate constants for the dehydration of HCO3? catalyzed by complexes Zn3L1, Zn3L2, Zn3L3, and Zn3L4 are 0.96, 2.53, 12.05, and 6.99 mol?1 dm3 s?1 respectively. At the same time, the pKa values 7.60, 7.16, 7.51, and 7.42 for the deprotonation of the Zn(II)‐bound water in the four catalysts were obtained, which are consistent with those that resulted from pH titrations, i.e. 7.47, 7.25, 7.52, and 7.38 respectively. The mechanism is proposed and the results are compared with other model complexes of carbonic anhydrase. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 197–203, 2004  相似文献   

    14.
    The [C4H6O] ion of structure [CH2?CHCH?CHOH] (a) is generated by loss of C4H8 from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔHf of [CH2?CHCH?CHOH] was estimated to be 736 kJ mol?1. The isomeric ion [CH2?C(OH)CH?CH2] (b) was shown to have ΔHf, ? 761 kJ mol?1, 54 kJ mol?1 less than that of its keto analogue [CH3COCH?CH2]. Ion [CH2?C(OH)CH?CH2] may be generated by loss of C2H4 from ionized hex-1-en-3-one or by loss of C4H8 from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C4H6O] ion generated by loss of C2H4 from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH2?CHCH?CHOH] and [CH2?C(OH)CH?CH2] ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH3˙ and CO, [CH2?CHCH?CHOH]+˙ and [CH2?C(OH)CH?CH2] do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C4H6O] ion [CH2?C?CHCH2OH] are also reported.  相似文献   

    15.
    Triplet—triplet absorption spectra in the 220–250 nm region, and rate constants for unimolecular and bimolecular decay of the lowest triplet states of simply substituted benzenes in the gas phase have been obtained using a phase modulation technique. For deuterium and methyl substitution, first order decay constants are of the same order as in benzene of 103 s?1, with second order decay constants of the order of 107 ? mol?1 s?1, also as in benzene. For trifluoromethyl substitution, these rate constants increase dramatically to of the order of 10?5 s?1 and 108 ? mol?1 s?1 respectively, and fluorine substitution is even more dramatic, with values in the 106 s?1 and 109 ? mol?1 s?1 respectively.  相似文献   

    16.
    The antioxidation properties of tocopherolhydroquinone were studied by the chemiluminescence method in combination with mathematical simulation. The rate constant of the liquid-phase reaction of tocopherolhydroquinone with the α-ethylphenylperoxy radical was determined (2.4 × 106 l mol?1 s?1). The rate constants of chain propagation in the reactions of the tocopherolhydroquinone radical with RH (≤0.07 l mol?1 s?1) and O2 (950 l mol?1 s?1) were estimated.  相似文献   

    17.
    The kinetics of the extraction of phenylsuccinic acid (PSA) enantiomers by hydroxypropyl-β-cyclodextrin (HP-β-CD) in a modified Lewis cell was studied, in which HP-β-CD dissolved in 0.1 mol L?1 NaH2PO4/H3PO4 buffer solution (pH = 2.5) was selected as the chiral extractant. PSA enantiomers were extracted from organic phase to aqueous phase in the extraction module. The theory of extraction accompanied by a chemical reaction has been used to obtain the intrinsic kinetics of this extraction module. The different parameters affecting the extraction rate such as agitation speed, interfacial area, initial concentration of PSA enantiomers in organic phase as well as HP-β-CD concentration in aqueous phase were separately studied. The experimental results demonstrate that the extraction reactions are fast. The reactions were found to be first order with respect to PSA and second order with respect to HP-β-CD with forward rate constants of 3.4 × 10?2 m6 mol?2 s?1 for R-PSA and 9.96 × 10?3 m6 mol?2 s?1 for S-PSA. These data will be useful in the design of extraction processes.  相似文献   

    18.
    The rate constants of the reactions of e aq ? and the OH· radical with the oxalate ion in a neutral aqueous solution were measured by means of the pulse radiolysis technique. They were found to be (3.5 ± 0.5) × 107 and (1.5 ± 0.2) × 107 l mol?1 s?1, respectively. The radical anion ?OOC-C·OO2? is characterized by an optical absorption band that has a maximum at 270 nm and a molar absorption coefficient of (2400 ± 200) l mol?1 cm?1. The radical anion ·OOC-COO?, the product of the reaction with the OH· radical, exhibits absorption that has no maximum and increases in intensity with a decrease in the wavelength extending to the UV region (?220 = 1800 l mol?1 cm?1). The mechanism of radiation-chemical transformations in aqueous oxalate solutions is discussed.  相似文献   

    19.
    A method of measuring the kinetics of currents arising at the electron photoemission from a metal into electrolyte solution when affected by the u.v. laser pulses for 10?8 s at the frequency of repetitions 10–25 Hz is described. Measurements have been taken in solutions without acceptors and in those containing N2O and NO2?, NO3? ions as electron acceptors. The rate constants of capture of the solvated electrons by N2O ((6±1)×09 mol?1 s?1) and NO2? ((4.5±1)×109 mol?1 s?1) and the diffusion coefficients of OH-radicals ((1.0±0.3)×10?5 cm2 s?1) and of NO ((1.2±0.3)×10?5 cm2 s?1) are found. The oxidation rate of NO32? has been shown to decrease from 40 cm s?1 in the range of potentials ?0.55 to ?1.0 V. The rate constant of bimolecular recombination of the solvated electrons ((1.3±0.4)×1010 mol?1 s?1) has been found from the dependence of the emitted charge on the light intensity.  相似文献   

    20.
    The kinetics of base hydrolysis of (αβ S)-(o -methoxy benzoato) (tetraethylenepentamine)cobalt(III) obeyed the rate law: kobs = kOH[OH?], in the range 0.05 ? [OH?]T, mol dm?3 ? 1.0, I = 1.0 mol dm?3, and 20.0–40.0°C. At 25°C, kOH = 13.4 ± 0.4 dm3 mol?1 s?1, ΔH = 93 ± 2 kJ mol?1 and ΔS = 90 ± 5 JK?1 mol?1. Several anions of varying charge and basicity, CH3CO2?, SO32?, SO42?, CO32?, C2O42?, CH2(CO2)22?, PO43?, and citrate3? had no effect on the rate while phthalate2?, NTA3?, EDTA4?, and DTPA5? accelerated the process via formation of the reactive ion pairs. The anionic (SDS), cationic (CTAB), and neutral (Triton X-100) micelles, however, retarded the reaction, the effect being in the order SDS> CTAB > Triton X-100. The importance of electrostatic and hydrophobic effects of the micelles on the selective partitioning of the reactants between the micellar and bulk aqueous pseudo-phases which control the rate are discussed. © 1994 John Wiley & Sons, Inc.  相似文献   

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