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Notes: The time-resolved total emission of SO2 (B1B1→X1A1) at 354.9 nm were monitored following the direct excitation by a 266 nm laser pulse. A three-level model was proposed to deal with SO2 (X1A1, A1A2, B1B1) system. From a kinetic treatment of these measurements, the coupling coefficient, ξ, and the relaxation time, τ, relating to the high vibronic levels of A1A2 and B1B1 states were first obtained. It is found that ξ and τ values keep basically constant, reflecting the characteristics of the studied system. In addition, the quenching rate constants of SO2 (A1A2, B1B1) by some alkane and chloromethane molecules were measured at room temperature. The formation cross sections of complexes of SO2 (A1A2, B1B1) and quenchers were calculated by means of a collision complex model. It is shown that the dependence of the formation cross section of complex on the number of C(SINGLEBOND)H or C(SINGLEBOND)Cl bonds is generally in agreement with that of the measured quenching cross section. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 831-837, 1998

Notes: Some relative rate experiments have been carried out at room temperature and at atmospheric pressure. This concerns the OH-oxidation of some oxygenated volatile organic compounds including methanol (k1), ethanol (k2), MTBE (k3), ethyl acetate (k4), n-propyl acetate (k5), isopropyl acetate (k6), n-butyl acetate (k7), isobutyl acetate (k8), and t-butyl acetate (k9). The experiments were performed in a Teflon-film bag smog chamber. The rate constants obtained are (in cm3 molecule-1 s-1): k1=(0.90±0.08)×10-12; k2=(3.88±0.11)×10-12; k3=(2.98±0.06)×10-12; k4=(1.73±0.20)×10-12; k5=(3.56±0.15)×10-12; k6=(3.97±0.18)×10-12; k7=(5.78±0.15)×10-12; k8=(6.77±0.30)×10-12; and k9=(0.56±0.11)×10-12. The agreement between the obtained rate constants and some previously published data has allowed for most of the studied compounds to point out a coherent group of values and to suggest recommended values. Atmospheric implications are also discussed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 839-847, 1998

Notes: The rate constant of the title reaction is determined during thermal decomposition of di-n-pentyl peroxide C5H11O(—)OC5H11 in oxygen over the temperature range 463-523 K. The pyrolysis of di-n-pentyl peroxide in O2/N2 mixtures is studied at atmospheric pressure in passivated quartz vessels. The reaction products are sampled through a micro-probe, collected on a liquid-nitrogen trap and solubilized in liquid acetonitrile. Analysis of the main compound, peroxide C5H10O3, was carried out by GC/MS, GC/MS/MS [electron impact EI and NH3 chemical ionization CI conditions]. After micro-preparative GC separation of this peroxide, the structure of two cyclic isomers (3S*,6S*)3α-hydroxy-6-methyl-1,2-dioxane and (3R*,6S*)3α-hydroxy-6-methyl-1,2-dioxane was determined from 1H NMR spectra. The hydroperoxy-pentanal OHC(—)(CH2)2(—)CH(OOH)(—)CH3 is formed in the gas phase and is in equilibrium with these two cyclic epimers, which are predominant in the liquid phase at room temperature. This peroxide is produced by successive reactions of the n-pentoxy radical: a first one generates the CH3C·H(CH2)3OH radical which reacts with O2 to form CH3CH(OO·)(CH2)3OH; this hydroxyperoxy radical isomerizes and forms the hydroperoxy HOC·H(CH2)2CH(OOH)CH3 radical. This last species leads to the pentanal-hydroperoxide (also called oxo-hydroperoxide, or carbonyl-hydroperoxide, or hydroperoxypentanal), by the reaction HOC·H(CH2)2CH(OOH)CH3+O2→O(=)CH(CH2)2CH(OOH)CH3+HO2.The isomerization rate constant HOCH2CH2CH2CH(OO·)CH3→HOC·HCH2CH2CH(OOH)CH3 (k3) has been determined by comparison to the competing well-known reaction RO2+NO→RO+NO2 (k7). By adding small amounts of NO (0-1.6×1015 molecules cm-3) to the di-n-pentyl peroxide/O2/N2 mixtures, the pentanal-hydroperoxide concentration was decreased, due to the consumption of RO2 radicals by reaction (7). The pentanal-hydroperoxide concentration was measured vs. NO concentration at ten temperatures (463-523 K). The isomerization rate constant involving the H atoms of the CH2(—)OH group was deduced:\documentclass{article}\pagestyle{empty}\begin{document}$ k_{3}\rm =(6.4\pm 0.6)\times 10^{10}\hbox{exp}\{-(16,900\pm 700)\hbox{cal mol}^{-1}/RT\}s^{-1} $\end{document}or per H atom:\documentclass{article}\pagestyle{empty}\begin{document}$ k_{3\rm (H)}\rm =(3.2\pm 0.3)\times 10^{10}\hbox{exp}\{-(16,900\pm 700)\hbox{cal mol}^{-1}/RT\}s^{-1} $\end{document}The comparison of this rate constant to thermokinetics estimations leads to the conclusion that the strain energy barrier of a seven-member ring transition state is low and near that of a six-member ring. Intramolecular hydroperoxy isomerization reactions produce carbonyl-hydroperoxides which (through atmospheric decomposition) increase concentration of radicals and consequently increase atmospheric pollution, especially tropospheric ozone, during summer anticyclonic periods. Therefore, hydrocarbons used in summer should contain only short chains (〈C4) hydrocarbons or totally branched hydrocarbons, for which isomerization reactions are unlikely. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 875-887, 1998

Notes: The kinetics of the title reactions have been studied using the discharge-flow mass spectrometic method at 296 K and 1 torr of helium. The rate constant obtained for the forward reaction Br+IBr→I+Br2 (1), using three different experimental approaches (kinetics of Br consumption in excess of IBr, IBr consumption in excess of Br, and I formation), is: k1=(2.7±0.4)×10-11 cm3 molecule-1s-1. The rate constant of the reverse reaction: I+Br2→Br+IBr (-1) has been obtained from the Br2 consumption rate (with an excess of I atoms) and the IBr formation rate: k-1=(1.65±0.2)×10-13 cm3molecule-1s-1. The equilibrium constant for the reactions (1,-1), resulting from these direct determinations of k1 and k-1 and, also, from the measurements of the equilibrium concentrations of Br, IBr, I, and Br2, is: K1=k1/k-1=161.2±19.7. These data have been used to determine the enthalpy of reaction (1), ΔH298°=-(3.6±0.1) kcal mol-1 and the heat of formation of the IBr molecule, ΔHf,298°(IBr)=(9.8±0.1) kcal mol-1. © 1998 John Wiley & sons, Inc. Int J Chem Kinet 30: 933-940, 1998

Notes: Detailed modeling of the oxidation of n-octane and n-decane in the gas phase was performed by using mechanisms written by means of a software recently developed in our laboratory. This computer-aided design of mechanisms permits the automatic generation of detailed oxidation and combustion kinetic models in the case of paraffins and isoparaffins [1]. For n-octane, the predictions of the model were compared with experimental results obtained by Dryer and Brezinsky by means of a turbulent plug flow reactor (1080 K, 1 atm) [2]. The experimental study of Balès-Guéret et al., performed in a perfectly stirred reactor (922-1033 K, 1 atm) [3], was used as a basis of comparison for the modeling of the oxidation of n-decane. Considering that no fitting of any kinetic parameter was done, the agreement between the computed and the experimental values is satisfactory both for conversions and for the distribution of the products formed. This modeling has required improvement in the generation of the secondary reactions of alkenes, which are the main primary products obtained during the oxidation of these two alkanes in the range of temperature studied and for which reaction paths are detailed. © 1998 John Wiley & Sons, Inc. Int J Chem Kinet 30: 949-959, 1998

Notes: The rate constant for the CF3 + NO2 reaction (k2) was measured at room temperature in the range of total pressures 300-600 torr. The measurements were performed using the ruby-laser-induced pulsed photodissociation of CF3NO in the presence of NO and NO2 in combination with time-resolved detection of the absorption of He(SINGLE BOND)Ne laser radiation by CF3NO. The use of the CF3 + NO reaction as a reference gives k2 = (3.2 ± 0.7) × 10-11 cm3/s. Analysis of the end products of the CF3 + NO2 reaction shows that the contribution of the association reaction channel, which leads to the formation of CF3NO2, is rather significant (about 30% total yield). A reaction mechanism is suggested to account for the products observed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 203-208, 1997.

Notes: The reaction between the radical cation derived from 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and phenols follows a kinetic law given by \documentclass{article}\pagestyle{empty}\begin{document}$$ d[ABTS^{\buildrel{+}\over{\cdot}}]/dt=k [ABTS^{\buildrel{+}\over{\cdot}}]^2[PhOH]/[ABTS] $$\end{document} with stoichiometric coefficients between one and two. The rate constant is almost unrelated to the structure of the phenol, while the number of ABTS radicals scavenged by each phenol molecule increases with para-substitution. These results are explained in terms of a fast, reversible electron transfer \documentclass{article}\pagestyle{empty}\begin{document}$$ ABTS^{\buildrel{+}\over{\cdot}}\,+PhOH {\buildrel{\longrightarrow}\over{\longleftarrow}} ABTS + PhO\bullet+H^{+} $$\end{document} followed by the self-combination of the phenoxy radicals and/or their reaction with another ABTS derived radical action. The relative rate of these processes determine the value of the stoichiometric coefficient. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 219-224, 1997.

Notes: Rate constants for H atom attack on GeH4 and GeD4 have been measured in pulsed photolysis experiments in which H atoms were produced by the mercury-sensitized photolysis of H2 and monitored by Lyman-α absorption. The values obtained for GeD4 in the temperature range 293-550 K may be represented by the expression \documentclass{article}\pagestyle{empty}\begin{document}$$ k_D=(0.99\pm 0.10)\times 10^{-10}\,exp[(-1114\pm 37)/T] $$\end{document} Combination of the rate constants for GeH4 measured in this work with those previously determined in this laboratory gives, for the temperature range 293-455 K, \documentclass{article}\pagestyle{empty}\begin{document}$$ k_H=(0.89\pm 0.08)\times 10^{-10}\,exp[(-879\pm 31)/T] $$\end{document} The kinetic isotope effect indicated by these expressions is given by \documentclass{article}\pagestyle{empty}\begin{document}$$ k_H/k_D=(0.90\pm 0.12)\,exp[(-235\pm 48)/T] $$\end{document} which yields \documentclass{article}\pagestyle{empty}\begin{document}$ k_H/k_D=2.0 \pm 0.4 hbox{ at 300 K.} $\end{document}. This is the first determination of the kinetic isotope effect for radical attack on a Ge(SINGLE BOND)H bond.The present results for the reaction of H atoms with GeH4 have been combined with previously reported data, and the best value for the rate constant over the temperature range 210-473 K is recommended to be \documentclass{article}\pagestyle{empty}\begin{document}$$ k_D=(1.18\pm 0.08)\times 10^{-10}\,exp[(-981\pm 22)/T] $$\end{document} © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 237-243, 1997.

Notes: A continuous flow-through reactor with a thin layer of solid particles (size ranging from 100 to 300 μm) was used to obtain a deeper knowledge on the mechanism of dissolution of UO2 under oxidizing conditions. Using this methodology the dissolution rate of uranium dioxide was determined at three different oxygen partial pressures (5, 21, and 100% in nitrogen) and as a function of pH (between 3 and 12) in a noncomplexing medium.From the results of these experiments the following rate equation was derived: \documentclass{article}\pagestyle{empty}\begin{document}$$ (3 〈 pH 〈 6.7)\,r\,(mol\cdot s^{-1}\cdot m^{-2})\,=\,(3.5 \pm 0.8) \cdot 10^{-8} \cdot [H^{+}]^{0.37\pm 0.01}\cdot[O_2]^{0.31\pm 0.02} $$\end{document} In addition, XPS characterizations were performed to determine the U(IV)/U(VI) ratio on the solid surface at different experimental times and conditions. These results showed that at acidic conditions (pH below 6.7) the final solid surface presents a stoichiometry close to UO2, while at alkaline conditions the final solid surface average composition is close to UO2.25. This information was integrated with the results of the leaching experiments to present a model for the mechanism of dissolution of uranium dioxide under the experimental conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 261-267, 1997.

Notes: Rates, Arrhenius parameters, and Hammett substituent constants are obtained for the gas-phase thermal elimination of ethyl benzoate (1) and ethyl 2 - thienyl -  (2), 3 - thienyl -  (3), 2 - furyl -  (4), 3 - furyl -  (5), 4 - pyridyl -  (6), 3 - pyridyl -  (7), and 2 - pyridylcarboxylate (8) esters. The log A/s-1 and the Ea/kJ mol-1 values of these esters averaged 13.60 and 216.3, respectively. The present results are compared with data previously reported for the corresponding isopropyl and t-butyl analogues, and the findings are rationalized in terms of a plausible transition state for the elimination pathway. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 289-293, 1997.

Notes: The aquation kinetics of [Co(NH3)5Cl]2+ in dicarboxylate media containing 10% (v/v) acetone is measured in the temperature range of 35-60°C. A new empirical correlation between the rate coefficient, kobs, and the stoichiometric concentration of the dicarboxylate ligand (CL) has been established and a reaction mechanism is proposed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 311-316, 1997.

Notes: Kinetics of the interaction of Cd(II)-histidine complex with ninhydrin has been carried out at pH 5.02 (acetic acid-sodium acetate buffer) under varying conditions of reactant concentrations, temperature, and surfactant concentrations. The order of the reaction with respect to Cd(II)-histidine complex was unity while it was fractional with respect to ninhydrin. On the basis of these studies a mechanism has been proposed. In the absence of the surfactants, the reaction followed rate equation: \documentclass{article}\pagestyle{empty}\begin{document}$$ {1\over k_{\rm obs}}={1\over k}+{1\over k K_t{\rm [Ninhydrin]}} $$\end{document} while, in presence of surfactants, the following rate equation was obeyed: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_\Psi={{k_W+K_mK_s[D_n]}\over{1+K_s[D_n]}} $$\end{document} Anionic micelles of sodium dodecyl sulphate catalyze the reaction with the rate reaching a maximum at ca. 0.10 mol dm-3 surfactant. The surfactant decreases activation enthalpy and makes it more negative. Cationic micelles of cetyltrimethylammonium bromide strongly inhibit the reaction and increase the activation enthalpy but make the activation entropy more positive than the SDS micelles. Added salts (KNO3 and NaCl) inhibit the catalysis, and the effect is more with the latter. The rate constants, binding constants with surfactants, and the index of cooperativity have been evaluated. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the oxidation of formate, oxalate, and malonate by |NiIII(L1)|2+ (where HL1 = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) were carried out over the regions pH 3.0-5.75, 2.80-5.50, and 2.50-7.58, respectively, at constant ionic strength and temperature 40°C. All the reactions are overall second-order with first-order on both the oxidant and reductant. A general rate law is given as - d/dt|NiIII(L1)2+| = kobs|NiIII(L1)2+| = (kd + nks |R|)|NiIII(L1)2+|, where kd is the auto-decomposition rate constant of the complex, ks is the electron transfer rate constant, n is the stoichiometric factor, and R is either formate, oxalate, or malonate. The reactivity of all the reacting species of the reductants in solution were evaluated choosing suitable pH regions. The reactivity orders are: kHCOOH 〉 kHCOO-; kH2ox 〉 kHox- 〉 kox2-, and kH2mal 〉 kHmal- 〈 kmal2- for the oxidation of formate, oxalate, and malonate, respectively, and these trends were explained considering the effect of hydrogen bonded adduct formation and thermodynamic potential. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 225-230, 1997.

Notes: The rate constant for the NH3 + NO2 rlhar2; NH2 + HONO reaction (1) has been kinetically modeled by using the photometrically measured NO2 decay rates available in the literature. The rates of NO2 decay were found to be strongly dependent on reaction (1) and, to a significant extent, on the secondary reactions of NH2 with NOX and the decomposition of HONO formed in the initiation reaction. These secondary reactions lower the values of k1 determined directly from the experiments. Kinetic modeling of the initial rates of NO2 decay computed from the reported rate equation, - d[NO2]/dt = k1[NH3][NO2] based on the conditions employed led to the following expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 10 ^{11.39\pm 0.16}\,e^{-(12620\pm 240)/T}\,cm^3 mole^{-1} s^{-1} $$\end{document} This result agrees closely with the values predicted by ab initio MO [G2M//B3LYP/6-311 G(d,p)] and TST calculations. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 245-251, 1997.

Notes: Na2(Mo2vO4EDTA).4H2O crystals have been prepared in pure form. Kinetics for the oxidation of the compound by S2O82- have been studied spectrophotometrically in dilute sulphuric acid medium. The effects of hydrogen ion concentration, metal ion concentration, S2O82- ion concentration, and temperature on the process have been studied. Rate equations have been derived to explain the experimental observations. On the basis of the observations, suitable mechanisms have been suggested. The kinetic parameters E*, ΔH≠, and ΔS≠ of the process have also been determined. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 269-274, 1997

Notes: The rates of gas-phase elimination reactions of methyl benzoylformate (1) and 3-hydroxy-3-methyl-2-butanone (2) were obtained at T = 600 K. The two substrates undergo unimolecular first-order elimination for which the Arrhenius equations are, respectively, log k = 13.2 - 53270/(4.574 × 600) for (1) and log k = 12.4 - 53060/(4.574 × 600) for (2). The products of pyrolysis of (1) are benzaldehyde, formaldehyde and CO, while those of (2) are acetaldehyde and acetone. The kinetics of the elimination reactions show benzoylformic acid to be 106-fold more reactive than (1), and pyruvic acid ca. 105-fold more reactive relative to (2); an indication of the rate-controlling part played by the acidity of the hydrogen atom involved in the elimination process of the present compounds in this particular type of reaction. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 295-298, 1997.

Notes: The transformation kinetics of a series of liquid-crystallines based on 1,4-phenylene 4-n-alkybenzoate-4-allyloxybenzoate (PABAOB) was studied by nonisothermal methods using differential scanning calorimetry. These determinations led to the values of activation energy of transformation from 691.3 to 628.3 kJ/mol, respectively. The values of the Avrami exponent n were from 3.0 to 2.6. The values of transformation activation energy decreased with the ascending of alkyl. The result shows that the process of transformation of PABAOB is a constant number of nuclei growing in three dimensions at constant rate and the crystal growth being controlled probably by a diffusion process. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 317-321, 1997

Notes: Rate constants for three dimethylbenzaldehydes and two trimethylphenols have been determined for the OH reactions at 298±2 K and atmospheric pressure using a relative rate method. The OH reaction rate constants were placed on an absolute basis using the literature rate constant for 1,2,4-trimethylbenzene of (3.25±0.5)×10-11 cm3 molecule-1s-1). The measured rate constants were (in units of cm3 molecule-1 s-1) 2,4-dimethyl-benzaldehyde, (4.32±0.67)×10-11; 2,5-dimethylbenzaldehyde, (4.37±0.68)×10-11; 3,4-dimethylbenzaldehyde, (2.14±0.34)×10-11; and 2,3,5- trimethylphenol, (12.5±1.9)×10-11, 2,3,6-trimethylphenol, (11.8±1.8)×10-11. Using an average OH concentration of 8.7×105 molecule cm-3, the estimated atmospheric lifetimes are ca. 7.5 h for 2,4- and 2,5-dimethylbenzaldehydes, ca. 15 h for 3,4-dimethylbenzaldehyde, ca. 2.5 h for 2,3,5- and 2,3,6-trimethylphenols. The reactivities of the trimethylphenols exceed those of the dimethyl-benzaldehydes by more than a factor of 3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 523-525, 1997.

Notes: The cracking reaction pathways and mechanisms of ethylcyclohexane and 1-cyclohexyloctane with a rare earth Y (REY) catalyst were studied. Experiments at 500°C indicated that the dominant reactions were ring opening with subsequent secondary cracking, cracking in the alkyl side chain, isomerization, and hydrogen transfer. A kinetic model of the catalytic cracking of 1-cyclohexyloctane was developed using a novel mechanism-based lumping scheme that exploits the chemical similarities within reaction families. The formal application of 17 reaction family matrices, which correspond to 13 reaction family classes, to the matrix representations of the reactants and derived products generated the model. The reaction family concept was further exploited to constrain the kinetics within each reaction family to follow a quantitative structure/reactivity Polanyi relationship. Ultimately, nine Polanyi relationship parameters and three coking/deactivation parameters were determined by optimizing the model fit to the experimental data. The resulting model correlations were excellent, as the overall parity between experimental and model values was yModel=-0.000470+0.986yExp with a correlation coefficient of 0.971. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 545-560, 1997.

Notes: CF3O2CF3 was photolyzed at 254 nm in the presence of CO in 760 torr N2 or air at 296 K in a static reactor. In N2, the products CF3OC(O)C(O)OCF3 and CF3OC(O)O2C(O)OCF3 were detected by FTIR spectroscopy. In air, the only observed products were CF2O and CO2 and a chain process, initiated by CF3O, was invoked for the conversion of CO to CO2. From both product studies, a mechanism for the CF3O initiated oxidation of CO was derived, involving the addition reaction CF3O2 + CO → CF3OC(O). The rate constant for the reaction CF3O + CO at 296 K at a total pressure of 760 torr air was determined to be k(CF3O + CO) = (5.0 ± 0.9) × 10-14 cm3 molecule-1 s-1. © 1997 John Wiley & Sons, Inc.

Notes: Using relative rate techniques the reactions of chlorine and fluorine atoms with HC(O)F have been determined to proceed with rate constants of k1 = (1.9 ± 0.2) × 10-15 and k2 = (8.3 ± 1.7) × 10-13 cm3 molecule-1 s-1, respectively. Stated errors reflect statistical uncertainty; possible systematic uncertainties could add additional 10% and 20% ranges to the values of k1 and k2, respectively. Experiments were performed at 295 ± 2 K and 700 torr total pressure of air. The results are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1997 John Wiley & Sons, Inc.

Notes: The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of ethyl 3-ethoxypropionate (EEP, CH3CH2(SINGLE BOND)O(SINGLE BOND)CH2CH2C(O)O(SINGLE BOND)CH2CH3). EEP reacts with OH with a bimolecular rate constant of (22.9±7.4)×10-12 cm3 molecule-1s-1 at 297±3 K and 1 atmosphere total pressure. In order to more clearly define EEP's atmospheric reaction mechanism, an investigation into the OH+EEP reaction products was also conducted. The OH+EEP reaction products and yields observed were: ethyl glyoxate (EG, 25±1% HC((DOUBLE BOND)O)C((DOUBLE BOND)O)(SINGLE BOND)O(SINGLE BOND)CH2CH3), ethyl (2-formyl) acetate (EFA, 4.86±0.2%, HC((DOUBLE BOND)O)(SINGLE BOND)CH2(SINGLE BOND)C((DOUBLE BOND)O)(SINGLE BOND)O(SINGLE BOND)CH2CH3), ethyl (3-formyloxy) propionate (EFP, 30±1%, HC((DOUBLE BOND)O)(SINGLE BOND)O(SINGLE BOND)CH2CH2(SINGLE BOND)C((DOUBLE BOND)O)(SINGLE BOND)O(SINGLE BOND)CH2CH3), ethyl formate (EF, 37±1%, HC((DOUBLE BOND)O)O(SINGLE BOND)CH2CH3), and acetaldehyde (4.9±0.2%, HC((DOUBLE BOND)O)CH3). Neither the EEP's OH rate constant nor the OH/EEP reaction products have been previously reported. The products' formation pathways are discussed in light of current understanding of oxygenated hydrocarbon atmospheric chemistry. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the self-reactions of HO2, CF3CFHO2, and CF3O2 radicals and the cross reactions of HO2 with FO2, HO2 with CF3CFHO2, and HO2 with CF3O2 radicals, were studied by pulse radiolysis combined with time resolved UV absorption spectroscopy at 295 K. The rate constants for these reactions were obtained by computer simulation of absorption transients monitored at 220, 230, and 240 nm. The following rate constants were obtained at 295 K and 1000 mbar total pressure of SF6 (unit: 10-12 cm3 molecule-1 s-1): k(HO2+HO2)=3.5±1.0, k(CF3CFHO2+CF3CFHO2)=3.5±0.8, k(CF3O2+CF3O2)=2.25±0.30, k(HO2+FO2)=9±4, k(CF3CFHO2+HO2)=5.0±1.5, and k(CF3O2+HO2)=4.0±2.0. In addition, the decomposition rate of CF3CFHO radicals was estimated to be (0.2-2)×103 s-1 in 1000 mbar of SF6. Results are discussed in the context of the atmospheric chemistry of hydrofluorocarbons. © 1997 John Wiley & Sons, Inc.

Notes: The relative importance of three different routes for the N- nitrosation of amino acids (nitrosation by N2O3, by NO+/NO2H2+ and by intramolecular migration of the nitroso group from the initially nitrosated carboxylate group) was investigated for methylaminobutyric acid, methylaminoisobutyric acid, azetidine-2-carboxylic acid, azetidine-3-carboxylic acid, indoline carboxylic acid, and phenylaminoacetic acid. Reaction kinetics were determined by the initial rate and Guggenheim methods, by spectrophotometric monitoring of the formation of nitroso amino acid. Kinetic parameters were calculated using a nonlinear optimization algorithm based on Marquardt's method. In the experimental rate equation the dominant term corresponds to nitrosation by dinitrogen trioxide, which experiments at various temperatures show to take place via an ordered transition state. Nitrosation by intramolecular migration is significant for substrates facilitating the formation of a transition state structure with a 5- or 6-membered ring. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 495-504, 1997.

Notes: The reaction rates of 2-chloro-3,5-dinitropyridine 1 with a series of arylthiolates 2a-h in methanol have been measured at 25°C. The products are the corresponding 2-thioaryl-3,5-dinitropyridine 3a-h. Good Hammett correlation with ρ value-1.19 was obtained suggesting an elimination-addition mechanism SNAr and the formation of Meisenheimer-like intermediates. Plot of log k2 vs. pKa values of arylthiols gave straight line with β=0.38 indicating that the π-bond breaking in the pyridine ring is so much advanced over bond making between the nucleophile and the carbon that bears the chlorine atom. Excellent correlation between log k2 and log K(carbon basicity of arylthiolates) was obtained. © 1997 John Wiley & Sons. Inc. Int J Chem Kinet 29: 515-521, 1997.

Notes: The recently developed I-atom atomic resonance absorption spectrometric(ARAS) technique has been used to study the thermal decomposition kinetics of CH3I over the temperature range, 1052-1820 K. Measured rate constants for CH3I(+Kr)→CH3+I(+Kr) between 1052 and 1616 K are best expressed by k(±36%)=4.36×10-9 exp(-19858 K/T) cm3 molecule-1 s-1. Two unimolecular theoretical approaches were used to rationalize the data. The more extensive method, RRKM analysis, indicates that the dissociation rates are effectively second-order, i.e., the magnitude is 61-82% of the low-pressure-limit rate constants over 1052-1616 K and 102-828 torr. With the known E0=ΔH00=55.5 kcal mole -1, the optimized RRKM fit to the ARAS data requires (ΔE)down=590 cm-1. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 535-543, 1997.

Notes: The use of hydrogen peroxide in addition to ferrous and ferric salts has been shown an effective method in the decoloration of indigocarmine (IDS), Indigo-5,5′-disulfonic acid disodium salt.The kinetic experiments control have been carried out by means of a conventional spectrophotometric technique. In acid medium and the initial absence of Fe+2, the decoloration process obeys the following rate law:\documentclass{article}\pagestyle{empty}\begin{document}$$ -{{d[\rm{IDS}]} \over {dt}} = k_{\exp}[\rm{IDS}] $$\end{document}Effects of reagents concentrations, temperature, and acidity on the rate experimental constant have been discussed. A feasible reaction mechanism is finally proposed. The rate equation deducted from the mechanism is according to the achieved experimental results. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the reactions of 2-chloro-3-nitropyridine (ortho-like) and 5-nitro (para-like) isomer with morpholine and piperidine were studied in methanol and benzene at several amine concentrations and temperatures in the range 25-45°C. The data show that k3-NO2/k5-NO2 ratios are less than unity in methanol. The steric hindrance in the transition state of the 3-nitro (ortho-like) isomer retards o-substitution while the stability of p-quinonoid structure of the 5-nitro (para-like) isomer favors p-substitution. In benzene, the k3-NO2/k5-NO2 ratios are greater than unity. The hydrogen bonding formation between the ammonium hydrogen and the ortho-nitro group in the transition state of 3-nitro isomer favors the o-substitution. © 1997 John Wiley & Sons, Inc.

Notes: The rate constant for the reaction of CH3OCH2 radicals with O2 (reaction (1)) and the self reaction of CH3OCH2 radicals (reaction (5)) were measured using pulse radiolysis coupled with time resolved UV absorption spectroscopy. k1 was studied at 296K over the pressure range 0.025-1 bar and in the temperature range 296-473K at 18 bar total pressure. Reaction (1) is known to proceed through the following mechanism:CH3OCH2 + O2 ↔ CH3OCH2O2# → CH2OCH2O2H# → 2HCHO + OH (kprod)CH3OCH2 + O2 ↔ CH3OCH2O2# + M → CH3OCH2O2 + M (kRO2)k = kRO2 + kprod, where kRO2 is the rate constant for peroxy radical production and kprod is the rate constant for formaldehyde production. The k1 values obtained at 296K together with the available literature values for k1 determined at low pressures were fitted using a modified Lindemann mechanism and the following parameters were obtained: kRO2,0 = (9.4 ± 4.2) × 10-30 cm6 molecule-2 s-1, kRO2,∞ = (1.14 ± 0.04) × 10-11 cm3 molecule-1 s-1, and kprod,0 = (6.0 ± 0.5) × 10-12 cm3 molecule-1 s-1, where kRO2,0 and kRO2,∞ are the overall termolecular and bimolecular rate constants for formation of CH3OCH2O2 radicals and kprod,0 represents the bimolecular rate constant for the reaction of CH3OCH2 radicals with O2 to yield formaldehyde in the limit of low pressure. kRO2,∞ = (1.07 ± 0.08) × 10-11 exp(-(46 ± 27)/T) cm3 molecule-1 s-1 was determined at 18 bar total pressure over the temperature range 296-473K. At 1 bar total pressure and 296K, k5 = (4.1 ± 0.5) × 10-11 cm3 molecule-1 s-1 and at 18 bar total pressure over the temperature range 296-523K, k5 = (4.7 ± 0.6) × 10-11 cm3 molecule-1 s-1. As a part of this study the decay rate of CH3OCH2 radicals was used to study the thermal decomposition of CH3OCH2 radicals in the temperature range 573-666K at 18 bar total pressure. The observed decay rates of CH3OCH2 radicals were consistent with the literature value of k2 = 1.6 × 1013exp(-12800/T)s-1. The results are discussed in the context of dimethyl ether as an alternative diesel fuel. © 1997 John Wiley & Sons, Inc.

Notes: Pseudo-first-order rate constants (k1 obs) for the reaction of MeNHOH with NCPH obey the relationship: k1 obs=k′b[MeNHOH]T2 where [MeNHOH]T represents total concentration of N-methylhydroxylamine buffer. The rate constants, k1 obs obtained at different total concentration of acetate buffer ([Buf]T) in the presence of 0.004 mol dm-3 MeNHOH follow the relationship: k1 obs=kb[Buf]T. The values of acetate buffer-catalyzed rate constant (kb) at different pH reveal the occurrence of both general base- and general acid- or general base-specific acid-catalysis in the reaction of MeNHOH with NCPH. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 647-654, 1997.

Notes: Two analytical models are presented to approximate the temperature dependent, rotationally-averaged vibrational-state-specific dissociation rate coefficient for collisions between diatomic molecules and rare gas atoms at combustion temperatures. The new models are derived by making simplifying approximations to a more detailed theoretical model recently reported in the literature. For accuracy, the first model requires, for a given collision pair, knowledge of the maximum vibrational quantum number, a single vibrational-rotational energy and an interaction parameter for dissociation, all of which are tabulated in this article for collisions of Ar with p-H2, O2, N2, and CO. This is in contrast to the recently reported theoretical model, which requires knowledge of all vibrational-rotational energies below the dissociation threshold, in addition to the interaction parameter for dissociation. The second model is simpler and more general than the first, but less accurate. To completely specify this model, knowledge of only the hard sphere cross section, and the characteristic temperatures for vibration and dissociation is required. The two analytical models are shown to agree well with the published theoretical values, with the accuracy of each model increasing with increasing temperature. The present models provide an accurate and efficient means of computing thousands or millions of rate coefficients for use in numerical simulations of combustion processes that couple kinetic equations with the governing equations of fluid dynamics. © 1997 John Wiley & Sons, Inc.

Notes: Experimental kineticists are always faced with the problem of reducing kinetic data to extract physically meaningful information. A particularly vexing problem arises when different models reproduce the data but yield different values for the physical parameters. For over forty-five years Monte Carlo simulation techniques have been used to study the statistical behavior of parameters extracted from data. Not only do these simulations provide realistic uncertainties, correlation coefficients, and confidence envelopes, but they also provide insight into the nature of the model. These insights may be obtained by viewing two-dimensional scatter plots of the fractional changes of the parameters and one-dimensional histograms of the distributions of the changes in the parameters. Monte Carlo simulations are illustrated with examples from OH+CH4 → CH3+H2O and the high-pressure rate coefficient for methyl-methyl association. A more complex problem involves models for pressure-dependent rate coefficients in the falloff region. We have modeled methyl-methyl association with five of the most current analytic approximations for behavior in the falloff region. All of these reproduce the data to within their uncertainties. However, when Monte Carlo techniques are applied the correlations between the parameters and the nonlinear nature of their behavior become evident. We postulate that the statistical behavior of the parameters of a model may be used to distinguish one model from another and, thereby, identify those analytic approximations that hold promise for further investigation and utilization. Finally, the recent advent of high-speed workstations implies that Monte Carlo simulations should become a routine part of the analysis of kinetic data. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 803-817, 1997

Notes: Fluorimetric titrations of 4-hydroxydiphenyl ether and its anion give stretched sigmoid curves with two inflection points. This reveals that the rates of excited state proton exchange are comparable to the rates of deactivation of the conjugate pair. These curves are analyzed using the lifetimes of the species. The excited state equilibrium constants determined from rate constants and by other methods are compared. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 861-867, 1997

Notes: Absolute rate coefficient for the gas-phase reaction of NO3 with 3-fluoropropene has been measured using the discharge-flow technique coupled to a LIF detection system for a range of temperatures from 296 K to 430 K. The measured room temperature rate constant is (0.39 ± 0.02) × 10-14 molecule-1 cm3 s-1. The Arrhenius expression k = (7.17 ± 3.34) × 10-12 exp[-(2248 ± 169)/T] is proposed for the reaction.The reactivity of alkenes containing halogen atoms is discussed and compared to that of simple alkenes, on the basis of the correlations between the reactivity against NO3 and the ionization potential of the alkenes.Tropospheric half life of 3-fluoropropene has been estimated at night and during daytime for typical NO3 and OH trophospheric concentrations. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 927-932, 1997.

Notes: The oxidation of substituted benzyl alcohols by bis(2,2′-bipyridyl) copper(II) permanganate (BBCP), leading to the corresponding benzaldehydes is first-order with respect to BBCP. Michaelis-Menten type kinetics were observed with respect to the alcohols. The oxidation of a,a-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect. The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Charton's triparametric LDR equation whereas ortho- substituted benzyl alcohols were correlated with a four parametric LDRS equation. The results of correlation analyses point to an electron-deficient reaction center in the transition state. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 9-16, 1997.

Notes: Absolute (flash photolysis) and relative (FTIR-smog chamber and GC) rate techniques were used to study the gas-phase reactions of Cl atoms with C2H6 (k1), C3H8 (k3), and n-C4H10 (k2). At 297 ± 1 K the results from the two relative rate techniques can be combined to give k2/k1 = (3.76 ± 0.20) and k3/k1 = (2.42 ± 0.10). Experiments performed at 298-540 K give k2/k1 = (2.0 ± 0.1)exp((183 ± 20)/T). At 296 K the reaction of Cl atoms with C3H8 produces yields of 43 ± 3% 1-propyl and 57 ± 3% 2-propyl radicals, while the reaction of Cl atoms with n-C4H10 produces 29 ± 2% 1-butyl and 71 ± 2% 2-butyl radicals. At 298 K and 10-700 torr of N2 diluent, 1- and 2-butyl radicals were found to react with Cl2 with rate coefficients which are 3.1 ± 0.2 and 2.8 ± 0.1 times greater than the corresponding reactions with O2. A flash-photolysis technique was used to measure k1 = (5.75 ± 0.45) × 10-11 and k2 = (2.15 ± 0.15) × 10-10 cm3 molecule-1 s-1 at 298 K, giving a rate coefficient ratio k2/k1 = 3.74 ± 0.40, in excellent agreement with the relative rate studies. The present results are used to put other, relative rate measurements of the reactions of chlorine atoms with alkanes on an absolute basis. It is found that the rate of hydrogen abstraction from a methyl group is not influenced by neighboring groups. The results are used to refine empirical approaches to predicting the reactivity of Cl atoms towards hydrocarbons. Finally, relative rate methods were used to measure rate coefficients at 298 K for the reaction of Cl atoms with 1- and 2-chloropropane and 1- and 2-chlorobutane of (4.8 ± 0.3) × 10-11, (2.0 ± 0.1) × 10-10, (1.1 ± 0.2) &times 10-10, and (7.0 ± 0.8) × 10-11 cm3 molecule-1 s-1, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 43-55, 1997.

Notes: Alkoxy and β-hydroxyalkoxy radicals are key intermediates formed in the atmospheric degradations of alkanes and alkenes, respectively. In the troposphere, these alkoxy radicals can decompose, isomerize, and react with O2. The literature data concerning the rates of these reactions are evaluated, and predictive schemes allowing the calculation of rate constants for these alkoxy radical reactions for atmospheric purposes are proposed. Good agreement between calculated reaction rates and experimental data concerning the absolute and relative importance of these reaction pathways is obtained, and alkoxy and β-hydroxyalkoxy radical reaction rates for radicals for which experimental data are not presently available can now be calculated for use in atmospheric modeling. © 1997 John Wiley & Sons, Inc.

Notes: N-atom concentration profiles were measured in highly diluted C2N2/NO/Ar reaction systems behind reflected shock waves at temperatures between 3050 K and 4430 K by applying atomic resonance absorption spectroscopy (ARAS). C2N2 served as a thermal source for CN radical which react with both, NO and the subsequently formed N atoms. Computer simulations based on a simplified reaction mechanism revealed strong sensitivity of the measured N atoms to the elementary reactions: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{cl} \rm{CN} + \rm{NO} {\buildrel{\it k}_5\over\rightleftharpoons} \rm{NCO} + \rm{N} & (\rm{R}5)\\ \rm {CN} + \rm{N} {\buildrel{\it k}_9\over\rightleftharpoons} \rm{C} + \rm{N}_2 & (\rm{R}9)\\ \end{array} $$\end{document} A fitting procedure of all experiments allowed determination of individual values of the rate coefficients: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{lr} \rm {\it k}_5\ =\ 9.6\times 10^{13}\ \exp(-21200K/T)\ cm^3\ mol^{-1}\ s^{-1} & (1)\\ \rm {\it k}_9\ =\ 1.9\ .\ .\ .\ 6.0\times 10^{13}\ cm^3\ mol^{-1}\ s^{-1} & (2)\\ \end{array} $$\end{document} The present results enlarge the temperature range of the recommended Arrhenius expression of k5 |1| and confirm recent measurements of the backward reaction of (R-9) |2,3|. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 35-41, 1997.

Notes: Published experimental studies concerning the determination of rate constants for the reaction F + H2 → HF + H are reviewed critically and conclusions are presented as to the most accurate results available. Based on these results, the recommended Arrhenius expression for the temperature range 190-376 K is kF+H2 = (1.1 ± 0.1) × 10-10 exp |-(450 ± 50)/T| cm3 molecule-1 s-1, and the recommended value for the rate constant at 298 K is kF+H2 = (2.43 ± 0.15) × 10-11 cm3 molecule-1 s-1. The recommended Arrhenius expression for the reaction F + D2 → DF + D, for the same temperature range, based on the recommended expression for kF+H2 and accurate results for the kinetic isotope effect kF+H2/kF+D2 is kF+D2 = (1.06 ± 0.12) × 10×10 exp |-(635 ± 55)/T|cm3 molecule-1 s-1, and the recommended value for 298 K is kF+D2 = (1.25 ± 0.10) × 10-11 cm3 molecule-1 s-1. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 67-71, 1997.

Notes: Rate constants have been measured for the reaction of OH radicals with four amides, R1N(CH3) - C(O)R2 (R1 = H or Methyl, R2 = Methyl or Ethyl), at 300 and 384 K using flash photolysis/resonance fluorescence. Reactants are introduced under slow flow conditions and are controlled by two independent methods, gas saturation and continuous injection. It turns out that the reactivities of the amides are considerably lower than those of the corresponding amines. The pattern of rate constants obtained at 300 K: 14, 21, 5.2, and 7.6 · 10-12 cm3/s for N,N-Dimethylacetamide (dmaa), N,N-Dimethylpropionamide (dmpa), N-Methylacetamide (maa), and N-Methylpropionamide (mpa), respectively, indicates a single, dominating reaction center and strong electronic effects of the substituents at both sides of the amide function. Correspondingly, the observed negative temperature dependence (E/R = - 400 to - 600 K) excludes a direct abstraction mechanism. © 1997 John Wiley & Sons, Inc.

Notes: The reactions of pyrrolidine with O-ethyl S-(X-phenyl) dithiocarbonates (X = 4-methyl, 4-methoxy, H, 4-chloro, 4-nitro, 2,4-dinitro, and 2,4,6-trinitro) are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (maintained with KCl). Pseudo-first-order kinetics are found under amine excess. Linear plots of the pseudo-first-order rate coefficient against concentration of free-base pyrrolidine are obtained for all the reactions, the nucleophilic rate coefficient (kN) being the slope of such plots. The Bronsted-type plot (log kN vs. pKa for the leaving group) is linear with slope βlg = - 0.2, which is consistent with a mechanism through a tetrahedral intermediate (T±) where its formation is rate determining. The βlg value is very similar to that found in the same reactions in water. There is a great difference in the mechanism of the reactions of O-ethyl S-phenyl dithiocarbonate with pyrrolidine (order one in amine) and piperidine (complex order in amine) in aqueous ethanol, and this is attributed to a greater nucleofugality from T± of piperidine rather than pyrrolidine. © 1997 John Wiley & Sons, Inc.

Notes: The deactivation of I(2P½) by R-OH compounds (R = H, CnH2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H2O, CH3OH, C2H5OH, n-C3H7OH, i-C3H7OH, n-C4H9OH, i-C4H9OH, s-C4H9OH, t-C4H9OH, are respectively, 2.4 ± 0.3 × 10-12, 5.5 ± 0.8 × 10-12, 8 ± 1 × 10-12, 10 ± 1 × 10-12, 10 ± 1 × 10-12, 11.1 ± 0.9 × 10-12, 9.8 ± 0.9 × 10-12, 7.1 ± 0.7 × 10-12, and 4.1 ± 0.4× 10-12 cm3 molec-1 s-1 at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the reactions of ground state oxygen atoms with 1-pentene, 1-hexene, cis-2-pentene, and trans-2-pentene was investigated in the temperature range 200 to 370 K. In this range the temperature dependences of the rate constants can be represented by k = A′ Tn exp(- E′a/RT) with A′ = (1.0 ± 0.6) · 10-14 cm3 s-1, n = 1.13 ± 0.02, E′a = 0.54 ± 0.05 kJ mol-1 for 1-pentene: A′ = (1.3 ± 1.2) · 10-14 cm3 s-1, n = 1.04 ± 0.08, E′a = 0.2 ± 0.4 kJ mol-1 for 1-hexene; A′ = (0.6 ± 0.6) · 10-14 cm3 s-1, n = 1.12 ± 0.05, E′a = - 3.8 ± 0.8 kJ mol-1 for cis-2-pentene; and A′ = (0.6 ± 0.8) · 10-14 cm3 s-1, n = 1.14 ± 0.06, E′a = - 4.3 ± 0.5 kJ mol-1 for trans-2-pentene. The atoms were generated by the H2-laser photolysis of NO and detected by time resolved chemiluminescence in the presence of NO. The concentrations of the O(3P) atoms were kept so low that secondary reactions with products are unimportant. © 1997 John Wiley & Sons, Inc.

Notes: For a number of hydrofluorocarbons (HFCs), EHez has been found to have a linear correlation with each of the following: (i) log (k/n); (ii) A/n; and (iii) Ea/R, where EH = HOMO energy of the molecule, z = average fractional positive charge on the abstractable hydrogen atom in the molecule, k = rate constant of the gas-phase H abstraction reaction of the molecule with OH radical at 298 K, n = number of abstractable H atoms in the molecule, A = preexponential factor, and Ea/R = activation temperature of the said reaction. These correlations have been used to estimate the temperature dependent rate constants for the reactions of OH radical with CF3CF2CH2CH2CF2CF3, CF3CH2CF2CH2CF3, CF3CF2CH2CH2F, CF3CH2CH3, CF3CH2CHF2, CF3CHFCH2F, and CHF2CHFCHF2 as {6.97 × 10-13 exp(1481/T)}, {5.43 × 10-13 exp(1754/T)}, {7.95 × 10-13 exp(l308/T)}, {8.0 × 10-13 exp(1300/T)}, {7.03 × 10-13 exp(1470/T)}, {7.33 × 10-13 exp(1417/T)}, and {8.09 × 10-13 exp(1285/T)}, respectively. These have not yet been measured experimentally. Linear correlation between EHez and log (k/n) has also been observed for nine halogen substituted acetaldehydes. On the other hand, EH is found to have a better linear correlation with log (k/n) than EHez in the case of fluorinated ethers and alcohols where the available experimental data are at present limited. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 187-194, 1997.

Notes: Rate coefficients for reactions between Cl radicals and four ketones were determined at 294 ± 1 K with a relative rate method using a laser photolysis technique. The experiments were conducted in synthetic air in a flow system at atmospheric pressure. A mixture of Cl2/ClONO2 was photolyzed and the formation of NO3 through the reaction Cl + ClONO2 → Cl2 + NO3 was measured with and without ketones in the reaction mixture. The NO3 radical concentration was measured by optical absorption using a diode laser as the light source. The rate coefficients for the Cl-ketone reactions could then be evaluated. The following rate coefficients were obtained (in units of cm3 molecule-1 s-1): cyclohexanone (7.00 ± 1.15) × 10-11; cyclopentanone (4.76 ± 0.33) × 10-11; acetone (1.69 ± 0.32) × 10-12; and 2,3-butanedione (7.62 ± 1.66) × 10-13. The accuracy of the method employed was tested by using the well-studied reaction between Cl and methane and a rate coefficient of (9.37 ± 1.04) × 10-14 cm3 molecule-1 s-1 was obtained, which is in good agreement with previous work. The errors are at the 95% confidence level. The results in this work indicate that a carbonyl group in a ketone lowers the reactivity towards α-hydrogen abstraction by Cl radicals, compared to the corresponding Cl-alkane reactions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 195-201, 1997.

Notes: Rate constants for the reactions of OH, NO3, and O3 with pinonaldehyde and the structurally related compounds 3-methylbutanal, 3-methylbutan-2-one, cyclobutyl-methylketone, and 2,2,3-trimethyl-cyclobutyl-1-ethanone have been measured at 300±5 K using on-line Fourier transform infrared spectroscopy. The rate constants obtained for the reactions with pinonaldehyde were: kOH=(9.1±1.8)×10-11 cm3 molecule-1 s-1, kNO3=(5.4±1.8)×10-14 cm3 molecule-1 s-1, and kO3=(8.9±1.4)×10-20 cm3 molecule-1 s-1. The results obtained indicate a chemical lifetime of pinonaldehyde in the troposphere of about two hours under typical daytime conditions, [OH]=1.6×106 molecule cm-3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 527-533, 1997.

Notes: To better understand the general interrelationships between chemical transformations and physical transformations in solid-state reactions, we have studied the kinetics of methyl transfer in polycrystalline samples of tetraglycine methyl ester [TGME] over the temperature range of 83°C-115°C. Changes in the concentrations of the reactant and various intermediates (sarcosyltriglycine methyl ester METGME, and tetraglycine TG) and products (sarcosyltriglycine METG and N N-dimethyl glycyl triglycine Me2TG) were measured over the entire time course of the reaction using HPLC. Corresponding measurements of physical transformations occurring during the course of the reactions were made using X-ray powder diffractometry and differential scanning calorimetry. Kinetic curves for the loss of TGME in the range of 83°C-115°C have a sigmoldal shape and collapse into one curve when plotted in terms of reduced time. t/t0.5, as do plots of intermediate and product concentration plotted in the same manner. The first 25% of the reaction proceeds homogeneously through what is believed to be the formation of a crystalline solid solution of the intermediates and products in the reactant. The acceleratory character of the kinetic curves in the single-phase portion of the reaction has been described by a kinetic scheme that contains a concentration-dependent rate constant. The apperance of a new crystalline phase beyond 35% of the reaction changes the reaction mechanism from a bulk reaction to an interface-controlled process that causes further acceleration of the methyl transfer. The apparent activation energies for both single-phase and heterophase stages of the reaction are about 100-130 kJ/mole © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 339-348, 1997

Notes: Relative rate constant measurements have been carried out on the Cl-atom reactions with benzene, chlorobenzene, toluene, xylene, and styrene in 740 torr of air at room temperature (295 K), using the photochemical reactor-FTIR spectroscopy technique. The Cl atoms were generated by the UV photolysis of Cl2, and the reference compounds were CHF, Cl for benzene and chlorobenzene and isobutane for toluene xylene and styrene. Using the absolute rate constant for these two reference compounds reported in the literature, the following kinetic data were obtained for the study compounds (in units of cm3s-1). \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{ll} {\rm Benzene} & (1.3\pm 0.3)\times 10 ^{-15}\\ {\rm Chlorobenzen} & (9.8\pm 2.4)\times 10 ^{-16}\\ {\rm Toluene} & (5.9\pm 0.5)\times 10 ^{-11}\\ o-{\rm Xylene} & (1.5\pm 0.1)\times 10 ^{-10}\\ m-{\rm Xylene} & (1.4\pm 0.1)\times 10 ^{-10}\\ p-{\rm Xylene} & (1.5\pm 0.1)\times 10 ^{-10}\\ {\rm Styrene} & (3.6\pm 0.3)\times 10 ^{-10}\end{array} $$\end{document} The quoted error bars are for ± 2σ. The present kinetic results are compared with available literature data to update and expand the kinetics database for Cl-atom reactions of organic compounds. The results are also analyzed to provide insights into the reaction mechanism for the Cl-atom initiated oxidation of benzene under atmospheric conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 349-358, 1997

Notes: The ligand substitution reaction Fe(CN)5H2O3- + pyrazine → Fe(CN)5 pyrazine3- + H2O has been studied in sodium dodecyl sulfate SDS, hexadecyltrimethylammonium bromide, CTAB, and salt aqueous solutions at 298.2 K. Kinetics were studied in dilute and concentrated salt solutions and in SDS and CTAB solutions at surfactant concentrations below and above the critical micelle concentration. Experimental results show that salt effects can be explained by considering the interaction between the cations present in the working media which come from the background electrolyte, and the Fe(CN)5H2O3- species in the vicinity of the cyanide ligands. This interaction makes the release of the aqua ligand from the inner-coordination shell of the iron(II) complex to the bulk more difficult resulting in a decrease of the reaction rate when the electrolyte concentration increases. Kinetic data in surfactant solutions show that not only micellized surfactants are operative kinetically, but also nonmicellized surfactants are influencing the reactivity. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 377-384, 1997

Notes: Solvent effects on the kinetics of aquation of [Co(dien)(en)Cl]2+ have been investigated within the temperature range (40-60°C) in acetone-water and ethanol-water media of varying solvent compositions up to 60% by weight of the organic solvent component. The variation of the activation paremeters (ΔG#, Δh#, and ΔS#) with the mole fraction of the organic solvent component was analyzed and discussed. The isokinetic plots were linear in both solvent systems and revealed the existence of compensation effect due to a strong solute-solvent interactions. The correlation of log k with the ionizing power (Y) was found to be linear in both solvent mixtures. Morever, the correlation of log k with D-1 was linear in case of ethanol-water medium while in case of acetone-water it was nonlinear. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 431-436, 1997.

Notes: The oxidation of ortho-, meta-, and para-substituted phenols by Quinolinium Dichromate (QDC) to the corresponding Quinones in aqueous acetic acid medium is first-order with respect to [QDC] and [phenol]. There is no effect of added Quinoline on rate. The reaction is acid catalyzed. A medium of low dielectric constant favors the oxidation process, and the rate of the oxidation process changes with change in the ionic strength of the medium. Electron releasing groups on the benzene ring enhance the rate of oxidation, while electron withdrawing groups retard, compared to the unsubstituted phenol. A correlation exists between log k2 and σ, the Hammett's substituent constant, with a slope of -3.79 at 303 K. Analysis of the rate data using σI and σR values indicate that both inductive and resonance effects of the substituents equally influence the rate of the reaction. The free energy of activation, ΔG≠, is linearly correlated with σ. A probable mechanism is proposed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 437-443, 1997.

Notes: The reaction of HCo(CO)4 (HT) or DCo(CO)4 (DT) with excess cinnamaldehyde (CA) in methylcyclohexane (RH) at 22.2° and under 1 atm of CO follows pseudo-first-order kinetics in HT or DT with an inverse isotopic effect of 0.54. Identified products of the reaction are hydrocinnamaldehyde (HCA) and styrene (STY). The STY is believed to be an artifact of the thermal decomposition of the true product PhCH2CH2C( (DOUBLE BOND) O)Co(CO)4 (X) or its isomer. Reduction of the carbon-carbon double bond in CA is effected by hydrogen from both the cobalt compound and RH. It is proposed that the reaction involves a free-radical chain mechanism in which the rate of the slow step is proportional to [CA]0n, the initial molar concentration of CA raised to a power of 1.5- 1.8. Additionally the rate of conversion of CA to HCA and X meets the criteria of a homocompetitive reaction with [CA], [HCA], and [STY] simple functions of t0.5 (where t is reaction time) for use of DT or (in a single case) a function of (t0.5 + t) for use of HT. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 473-481, 1997.

Notes: NO2 concentration profiles in shock-heated NO2/Ar mixtures were measured in the temperature range of 1350-2100 K and pressures up to 380 atm using Ar+ laser absorption at 472.7 nm, IR emission at 6.25±0.25 μm, and visible emission at 300-600 nm. In the course of this study, the absorption coefficient of NO2 at 472.7 nm was measured at temperatures from 300 K to 2100 K and pressures up to 75 atm. Rate coefficients for the reactions NO2+M→NO+O+M (1), NO2+NO2→2NO+O2 (2a), and NO2+NO2→NO3+NO (2b) were derived by comparing the measured and calculated NO2 profiles. For reaction (1), the following low- and high-pressure limiting rate coefficients were inferred which describe the measured fall-off curves in Lindemann form within 15% [FORMULA] The inferred rate coefficient at the low- pressure limit, k1o, is in good agreement with previous work at higher temperatures, but the energy of activation is lower by 20 kJ/mol than reported previously. The pressure dependence of k1 observed in the earlier work of Troe[1] was confirmed. The rate coefficient inferred for the high pressure limit, k1∞, is higher by a factor of two than Troe's value, but in agreement with data obtained by measuring specific energy-dependent rate coefficients.For the reactions (2a) and (2b), least-squares fits of the present data lead to the following Arrhenius expressions: [FORMULA] For reaction (2), the new data agree with previously recommended values of k2a and k2b, although the present study suggests a slightly higher preexponential factor for k2a. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 483-493, 1997.

Notes: 6-(Triphenylphosphonio-3′-cyclopentadienyl)-2,3,5-trihalocyclohexa-2,5-diene-1,4-diones (2) are a new class of phosphorus containing dyes that behave as weak bases. Mono-protonation occurs at the cyclopentadiene ring leading to three isomers as assessed by NMR. The kinetics of the protonation were studied by the stopped-flow technique in aprotic media. The activation energies and deuterium isotope effects suggest that the rate-limiting step is the addition of trifluoroacetic acid to the quinone ring rather than direct protonation of the cyclopentadiene ring. © 1997 John Wiley & Sons, Inc.

Notes: The Cl- and Br- initiated oxidations of CHCl(DOUBLEBOND)CCl2 in 700 torr of air at 296 K have been studied using a Fourier transform infrared spectrometer. Rate constants k(Cl+CHCl(DOUBLEBOND)CCl2)=(7.2±0.8)×10-11 and k(Br+CHCl(DOUBLEBOND)CCl2)=(1.1±0.4)×10-13 cm3 molecule-1 s-1 were determined using a relative rate technique with ethane and ethylene as references, respectively. The major products observed were CHXClC(O)Cl, (X=Cl or Br), CHClO, and CCl2O. Combining results obtained for the Cl-initiated oxidation of CHCl2(SINGLEBOND)CHCl2, we deduced that Cl-addition on trichloroethylene occurs via channel 1a, Cl+CHCl(DOUBLEBOND)CCl2→ CHCl2(SINGLEBOND)CCl2, (100±12)%. Self-reaction of the subsequently generated peroxy radicals CHCl2(SINGLEBOND)CCl2O2 leads to CHCl2CCl2O radicals which were found to decompose via channel 8a, CHCl2C(O)Cl+Cl, (91±11)% of the time, and channel 8b, CHCl2+CCl2O, (9±2)%. The reaction Br+CHCl(DOUBLEBOND)CCl2→CHBrCl(SINGLEBOND)CCl2 (17a) accounted for ≥(96±11)% of the total reaction. Decomposition of the CHBrCl(SINGLEBOND)CCl2O radicals proceeds (≥93±11)% via CHBrClC(O)Cl+Cl. As part of this work, k(Cl+CHCl2C(O)Cl)=(3.6±0.6)×10-14 and k(Cl+CHCl2(SINGLEBOND)CHCl2)=(1.9±0.2)×10-13 cm3 molecule-1 s-1 were measured. Errors reported above include statistical uncertainties (2σ) and estimated systematic uncertainties. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 695-704, 1997.

Notes: The OH radical yields generated in the ozonolysis of ethene (ET), propene (PR), cis-2-butene (CB), trans-2-butene (TB), 2,3-dimethyl-2-butene (TME), and isoprene (ISP) in the presence of 20 Vol.% O2 have been determined in a darkened glass reactor at 1 bar total pressure. The hydroxyl radicals formed were scavenged by an excess of CO added to the systems. The O2 present converted H atoms formed in this reaction into HO2. From measurements of the increase in CO2 generation by FTIR the OH formation yields were determined to be 0.08 (ET), 0.18 (PR), 0.17 (CB), 0.24 (TB), 0.36 (TME), and 0.19 (ISP), respectively, per molecule of reacted ozone. The combined error in the OH determinations is estimated to be 〈10%. © 1997 John Wiley & Sons, Inc.

Notes: An investigation is presented on the kinetics of complexation of aqueous solution of octacyanomolybdate (IV) and -tungstate (IV) after photoinitiation with one of the mixed group ligands containing both N and O, diethanolamine (DEOA), [NH(CH2CH2OH)2]. Under the steady state conditions and with approximation k3 〉 k4 over a range of concentrations, the observed rate law is:\documentclass{article}\pagestyle{empty}\begin{document}$$ \cal{k}_{\rm obs.}={\cal{k}_{2}\cal{k}_{4}\rm {I}_{a}[\rm {OH}^{-}][\rm {NH}(\rm{CH}_{2}\rm{CH}_{2}\rm{OH})_{2}]\over \rm{I}+\it \cal{k}_{2}[\rm {OH}^{-}]} $$\end{document}The complexes show shift in electronic transition supporting the mechanism of association of the ligand followed by the abstraction of some small molecules and then substitution by the ligand. The presence of the specific isobestic point also contributes towards the stability of the complex. The rate constant and quantum yield values are dependent on both the concentration of the metal cyanide and the ligand predicting the mechanism to be an associative one. The complexes have strong absorption in the visible range and are assigned metal-to-ligand electron transfer transition. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 819-824, 1997

Notes: It is shown experimentally that pentafluoroethane undergoes rapid protium-deuterium exchange with water in the presence of hydroxide ion. Addition of dimethylsulfoxide enhances the rate at least by a factor of 100. The first measured fractionation factor data are presented for the temperature range of 50-120°C. These values are compared with the theoretical estimations calculated by using isotopic reduced partition function ratios based on molecular vibrational frequencies. Although catalytic exchange is slow at ambient temperature, the reaction rate becomes measureable above around 60°C because of large activation energy (92 kJ/mole). Comparisons are made with similar data available for various halomethane and haloethane systems. © 1997 John Wiley & Sons, Inc.

Notes: Rate constants are reported for substitution at vanadium(IV) in bis-cyclopentadienylvanadium dichloride by a range of anionic and uncharged nucleophiles in acetonitrile solution. Rate constants have been determined for replacement of the first and of the second chloride. The reactivity of V(cp)2Cl2 is compared with that of Ti(cp)2Cl2. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 835-838, 1997

Notes: Ignition delay times of acetonitrile (CH3CN) in mixtures containing acetonitrile and oxygen diluted in argon were studied behind reflected shock waves. The temperature range covered was 1420-1750 K at overall concentrations behind the reflected shock wave ranging from 2 to 4×10-5 mol/cm3. Over this temperature and concentration range the ignition delay times varied by approximately one order of magnitude, ranging from ca. 100 μs to slightly above 1 ms. From a total of some 70 tests the following correlation for the ignition delay times was derived: tign=9.77×10-12 exp(41.7×103/RT)×{[CH3CN]0.12[O2]-0.76[Ar]0.34} s, where concentrations are expressed in units of mol/cm3 and R is expressed in units of cal/(K mol). The ignition delay times were modeled by a reaction scheme containing 36 species and 111 elementary reactions. Good agreement between measured and calculated ignition delay times was obtained. A least-squares analysis of 60 computed ignition delay times from six different groups of initial conditions gave the following temperature and concentration dependence: E=46.2×103 cal/mol, βCH3CN=0.43, βO2=-1.18, and βAr=0.18. The ignition process is initiated by H-atom ejection from acetonitrile. The addition of oxygen atoms to the system from the dissociation of molecular oxygen and from the reaction CH3CN+O2 → HO2·+CH2CN·is negligible. In view of the relatively high concentration of methyl radicals obtained in the reaction CH3CN+H → CH3+HCN, the branching step CH3+O2 → CH3O+O plays a more important role than the parallel step H+O2→ OH+O. A discussion of the mechanism in view of the sensitivity analysis is presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 839-849, 1997

Notes: The gas-phase reaction of ozone with vinylcyclohexane and methylene cyclohexane has been investigated at ambient T and p=1 atm of air in the presence of sufficient cyclo-hexane or 2-propanol added to scavenge OH. The reaction rate constants, in units of 10-18 cm3 molecule-1 s-1, are 7.52±0.97 for vinylcyclohexane (T=292±2 K) and 10.6±1.9 for methylene cyclohexane (T=293±2 K). Carbonyl reaction products were cyclohexyl meth-anal (0.62±0.03) and formaldehyde (0.47±0.04) from vinylcyclohexane and cyclohexanone (0.55±0.10) and formaldehyde (0.60±0.05) from methylene cyclohexane, where the yields given in parentheses are expressed as carbonyl formed, ppb/reacted ozone, ppb. The sum of the yields of the primary carbonyls is close to the value of 1.0 that is consistent with the simple mechanisms: O3+cyclo(C6H11)-CH(DOUBLEBOND)CH2→α(HCHO+cyclo(C6H11)CHOO)+(1-α)(HCHOO+cyclo(C6H11)CHO) for vinylcyclohexane and O3+(CH2)5C(DOUBLEBOND)CH2→α(HCHO +(CH2)5COO)+(1-α)(HCHOO+(CH2)5C(DOUBLEBOND)O) for methylene cyclohexane. The coefficients α are 0.43±0.10 for vinylcyclohexane and 0.52±0.05 for methylene cyclohexane, i.e., (formaldehyde+the substituted biradical) and (HCHOO+cyclohexyl methanal or cyclo-hexanone) are formed in ca. equal yields. Reaction rate constants, carbonyl yields, and reaction mechanisms are compared to those for alkene structural homologues. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 855-860, 1997

Notes: The reaction \documentclass{article}\pagestyle{empty}\begin{document}$\rm {H + HI}\mathop\rightarrow\limits ^{1}\rm {H}_{2}+\rm {I}$\end{document} was studied at 298 K and millitorr pressures employing the “Very Low Pressure Reactor” (VLPR) kinetic technique. H-atoms were generated by dissociating H2 molecules (of a H2/Ar mixture) in a microwave discharge cavity that preceded the very low pressure well-mixed reaction vessel. Quadrupole mass spectrometry was used to analyze molecules and atoms. The mass signal intensities of I and HI were measured at both 20 and 40 eV ionizing potentials while those of H and H2 were measured at 40 eV due to the very weak signal of these species at lower ionization potentials. Three different exit flow orifices were utilized in the reported VLPR experiments of about 2, 3, and 5 mm inner diameter to vary the species concentration under steady-state reaction conditions. A rate constant of k1=(2.1±0.2)×10-11 cm3/molecule.s was determined for the forward reaction at 298 K, which lies between the two previously reported values directly measured at 298 K. Satisfactory mass balance relations were obtained for the iodine atoms (from the HI and I species) which were better than 90% for most of the experiments. The value of the reported rate constant (k1) is 14.3% higher than the value measured by Umemoto et al. [6], and 33.3% lower than the value measured by Lorenz et al. [4]. Based on this comparison, the activation energy E1 of the forward reaction probably lies between those two previously reported values of 580 and 720 cal/mol. Transition State Calculations of A1 and A2 for the reaction of \documentclass{article}\pagestyle{empty}\begin{document}$\rm {H + I}_{2}\mathop\rightarrow\limits ^{2}\rm {HI + I}$\end{document} are in good agreement with the data on both reactions and suggest an activation energy of about 500±100 cal/mol for E2.© 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 915-925, 1997.

Notes: Time-resolved frequency-modulation spectroscopy is shown to be an effective method for measuring the rates of gas-phase reactions. As an example, the rate constant for the reaction of CN with C2H4 at 298 K is measured to be 2.5 ± 0.2 × 10-10 cm3s-1, in good agreement with other literature values. The efficiency and sensitivity of this technique will be of interest to the chemical kineticist. © 1997 John Wiley & Sons, Inc.

Notes: The laser photolysis-long path transient absorption technique was used to study the mechanism and products of the reaction O(3P) + OClO (→M) Products (3) at 260 K in 100 to 400 torr of He, N2, and Ar. ClO was not detected as a reaction product, 〈5% yield, from this reaction at 400 torr and 260 K. A broad UV absorption feature associated with a product of this reaction, with a peak located at 260 nm, was observed. The peak absorption cross section of this species was measured to be (1.72 ± 0.12) × 10-17 cm2 molecule-1. The rate coefficient for the appearance of this species was measured to be (1.69 ± 0.46) × 10-13 cm3 molecule-1 s-1 and was independent of pressure. The rate coefficient for the appearance of the species is ca. 10 times lower than that for the disappearance of O(3P), indicating that the observed species is not a direct product of the reaction of O(3P) with OClO. Mechanistic considerations and the possible identity of the absorber are discussed. © 1997 John Wiley & Sons, Inc.

Notes: Iron(III)-2,2′-bipyridyl complex obtained, in situ, by direct mixing of iron(III) and 2,2′-bipyridyl, oxidizes aniline, thiourea, and ascorbic acid. The reaction is markedly accelerated by sodium dodecyl sulphate. The rate-[surfactant] profile exhibits a maximum. The kinetic analysis of the micellar effect has been carried out using Berezin's approach. The binding constants of 2,2′-bipyridyl, aniline, thiourea, and ascorbic acid have been determined. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 171-179, 1997.

Notes: Rate constants k1, k2, and k3 have been measured at 298 K by means of a laser photolysis-laser magnetic resonance technique and (or) by a laser photolysis-infrared chemiluminescence detection technique (LMR and IRCL, respectively). \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{llclrr} {\rm Cl}+{\rm I}_2\longrightarrow {\rm ICl}+{\rm I}; & k_1 & = & (2.5\pm 0.7)\times 10^{-10} & ({\rm IRCL}) & (1)\\ & k_1 & = & (2.8\pm 0.8)\times 10^{-10} & ({\rm LMR}) & \\ {\rm SiCl}_3+{\rm I}_2\longrightarrow {\rm SiCl}_3{\rm I}+{\rm I}; & k_2 & = & (5.8\pm 1.8)\times 10^{-10} & ({\rm IRCL}) & (2)\\ {\rm SiH}_3+{\rm I}_2\longrightarrow {\rm SiIH}_3+{\rm I}; & k_3 & = & (1.8\pm 0.46)\times 10^{-10} & ({\rm LMR}) & (3)\\ \end{array} $$\end{document} As an average of the LMR and IRCL results we offer the value k1 = (2.7 ± 0.6) × 10-10. Units are cm3 molecule-1 s-1; uncertainties are 2σ including precision and estimated systematic errors. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 25-33, 1997.

Notes: By conducting an excimer laser photolysis (193 and 248 nm) behind shock waves, three elementary reactions important in the oxidation of H2S have been examined, where, H, O, and S atoms have been monitored by the atomic resonance absorption spectrometry. For HS + O2 → products (1), the rate constants evaluated by numerical simulations are summarized as: k1 = 3.1 × 10-11exp|-75 kJ mol-1/RT| cm3molecule-1s-1 (T = 1400-1850 K) with an uncertainty factor of about 2. Direct measurements of the rate constants for S + O2 → SO + O (2), and SO + O2 → SO2 + O (3) yield k2 = (2.5 ± 0.6) × 10-11 exp|-(15.3 ± 2.5) kJ mol-1/RT| cm3molecule-1s-1 (T = 980-1610 K) and, k3 = (1.7 ± 0.9) × 10-12 exp|-(34 ± 11) kJ mol-1/RT| cm3molecule-1s-1 (T = 1130-1640 K), respectively. By summarizing these data together with the recent experimental results on the H(SINGLE BOND)S(SINGLE BOND)O reaction systems, a new kinetic model for the H2S oxidation process is constructed. It is found that this simple reaction scheme is consistent with the experimental result on the induction time of SO2 formation obtained by Bradley and Dobson. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 57-66, 1997.

Notes: Rate constants for the reaction of 1-chloro-2,3-epoxypropane with p-cresol in the presence of basic catalysts were studied at the temperature range of 71-100°C.It was found that in the presence of sodium p-cresolate, three consecutive reactions proceeded giving the following products: 1-chloro-3-(tolyloxy)-2-propanol (CTP), 1-(p-tolyloxy)-2,3-epoxypropane (TEP) as a main product, and 1,3-di(p-tolyloxy)-2-propanol (DTP). Their rate constants at 71°C were: k1 = 0.030 ± 0.009, k2 = 1.58 ± 0.02, and k3 = 0.033 ± 0.005 dm3/mol · min, respectively.In the presence of quaternary ammonium salts, this process consisted of 5 reactions which led to CTP as a main product as well as TEP and 1,3-dichloro-2-propanol (DCP). The rate constant of CTP formation at 71°C was established, k1 = 0.130 ± 0.030 dm3/mol · min, as were the ratios of the other rate constants k2/k-4 = 1.5 ± 0.2, k5/k-4 = 20.0 ± 5.0, and k4/k1 = 0.6 ± 0.7. Based on the changes in Cl- ion concentration during the reaction, the catalystic activity of quaternary ammonium salts was explained.The kinetic model of these reactions in the presence of basic catalysts has been proposed and appropriate kinetic equations have been presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 73-79, 1997.

Notes: The chlorine transfer reaction between 3-azabicyclo[3,3,0]octane “AZA” and chloramine was studied over pH 8-13 in order to follow both the amination and halogenation properties of NH2Cl. The results show the existence of two competitive reactions which lead to the simultaneous formation of N-amino- and N-chloro- 3-azabicyclo[3,3,0]octane by bimolecular kinetics. The halogenation reaction is reversible and the chlorine derivative obtained, which is thermolabile and unstable in the pure state, was identified by electrospray mass spectrometry. These phenomena were quantified by a reaction between neutral species according to an apparent SN2-type mechanism for the amination process and a ionic mechanism involving a reaction between chloramine and protonated amine for the halogenation process. Amination occurs only in strongly basic solutions (pH ≥ 13) while chlorination occurs at lower pH's (pH ≤ 8). At intermediate pH's, a mixture of these two compounds is obtained. The relative proportions of the products are a function of intrinsic rate constants, pH and pKa of the reactants. The rate constants and thermodynamic activation parameters are the following: k1 = 45.5 × 10-3 M-1 s-1; ΔH10# = 59.8 kJ mol-1; ΔS10# = - 86.5 J mol-1 K-1 for amination; k2 = 114 × 10-3 M-1 s-1; ΔH20# = 63.9 kJ mol-1; and ΔS20# = - 48.3 J mol-1 K-1 for chlorination. The ability of an interaction corresponding to a specific(NH3Cl+/RR′NH) or general (NH2Cl/RR′NH) acid catalysis has been also discussed. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the reactions between sodium nitrite and phenol or m-, o-, or p-cresol in potassium hydrogen phthalate buffers of pH 2.5-5.7 were determined by integration of the monitored absorbance of the C-nitroso reaction products. At pH 〉 3, the dominant reaction was C-nitrosation through a mechanism that appears to consist of a diffusion-controlled attack on the nitrosatable substrate by NO+/NO2H2+ ions followed by a slow proton transfer step; the latter step is supported by the observation of basic catalysis by the buffer which does not form alternative nitrosating agents as nitrosyl compounds. The catalytic coefficients of both anionic forms of the buffer have been determined. The observed order of substrate reactivities (o-cresol ≈ m-cresol 〉 phenol ≫ p-cresol) is explained by the hyperconjugative effect of the methyl group in o- and m-cresol, and by its blocking the para position in p-cresol. Analysis of a plot of ΔH# against ΔS# shows that the reaction with p-cresol differs from those with o- and m-cresol as regards the formation and decomposition of the transition state. The genotoxicity of nitrosatable phenols is compared with their reactivity with NO+/NO2H2+. © 1997 John Wiley & Sons, Inc.

Notes: A laser-flash photolysis/UV absorption technique has been used to study the temperature dependence (from T = 300 - 470 K) of the self-reaction kinetics of representative primary secondary and tertiary β-hydroxyperoxy radicals \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{lclr} 2\,\rm{HOCH}_2\rm{CH}_2\rm{O}_2 & \longrightarrow & 2\,\rm{HOCH}_2\rm{CH}_2\rm{O}\,+\,\rm{O}_2 & (1\rm{a})\\ & \longrightarrow & \rm{HOCH}_2\rm{CH}_2\rm{OH}\,+\rm{HOCH}_2\rm{CH}_2\rm{O}\,+\,\rm{O}_2 & (1\rm{b})\\ 2\,\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}_2 & \longrightarrow & 2\,\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}\,+\,\rm{O}_2 & (2\rm{a})\\ & \longrightarrow & \rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{OH} & \\ & &+\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}+\rm{O}_2 & (2\rm{b})\\ 2\,\rm{HOC}(\rm{CH}_3)_2\rm{C}(\rm{CH}_3)_2\rm{O}_2 & \longrightarrow & 2\,\rm{HOC}(\rm{CH}_3)_2 \rm{C}(\rm{CH}_3)_2\rm{O}\,+\,\rm{O}_2 & (3)\\ \end{array} $$\end{document} The following Arrhenius expressions were derived for the rate coefficients of reactions (1)-(3) (in cm3 molecule -1s-1) and for the product branching ratios of reactions (1) and (2) as a function of temperature (all errors 1σ) \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l}k_1=(6.9_{+2.1}^{-1.5})\times 10 ^{-14}\,\exp[(1040\pm 100)/\rm{T}]\\ \beta_1=(3100_{+3700}^{-1700})\,\exp[(-2400\pm 280)/\rm{T}] (\hbox{ where } \beta_1=k_{1a}/k{1\rm{b}})\\ k_2=(7.7_{+12.8}^{-4.8})\times 10 ^{-15}\,\exp[(1330\pm 350)/\rm{T}]\\ \beta_2=(4.0_{+0.2}^{-0.1})\times 10 ^{4}\,\exp[(-3600\pm 100)/\rm{T}]\\ k_3=(4.7_{+6.5}^{-2.7})\times 10 ^{-13}\,\exp[(-1420\pm 320)/\rm{T}]\\ \end{array} $$\end{document} The calculated rate coefficients for reactions (1)-(3) at 298 K are therefore (in 10-13 cm3molecule -1s -1 23 ± 2, 6.7 ± 1.3, and 0.040 ± 0.012, respectively which compare well with the values measured elsewhere at this temperature using a similar technique. The product branching ratios and the Arrhenius parameters are compared with those for other substituted and unsubstituted peroxy radical self reactions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 323-331, 1997

Notes: Effect of some tert-amines on the catalytic osmium tetroxide dihydroxylation of cyclohexene in aqueous tert-butyl alcohol has been investigated All amines have been found to retard the catalysis greatly and beyond a definite concentration of amine, the rate reaches a minimal and remains constant. The oxidation of cyclohexene is inhibited by pyridine, 2.2′-bipyridyl and DABCO with an inverse first-order dependence whereas inhibition by triphenylamine NN-diethylaniline, picoline pyrazine hexamethylenetetraamine and TMEDA shows an inverse partial order dependence. The inolvement of dioxomonoglycolatoosmium(VI) esters and their monoamine adducts in the rate determining oxidation step was established by the linear plots of 1/Δk2 vs. 1/[L] where Δk2 is the decrease in the second-order rate constant in the presence of [L] concentration of tert-amine. The ligand-accelerated or ligand-decelerated catalysis of tert-amines in the catalytic osmium tetraoxide dihydroxylation of alkenes may vary depending on the secondary oxidant on the alkene and on the structure and concentration of the tert-amine. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 359-366, 1997

Notes: The alkaline hydrolysis of p-chloranil or 2,3,5,6-tetrachloro-1,4-benzoquinone (C6Cl4O2, Q) was studied, using stopped flow spectrophotometry and Electron Spin Resonance techniques (E.S.R.). In the present study it was shown for the first time, that a free radical is produced chemically and that it can account for the propagation of the reaction. It was found that in alkaline conditions chloranil in a “Michael” fashion undergoes 1,2 addition being hydrolyzed and in turn produces a chloranil free radical (Q•) The hydrolysis then proceeds via a number of intermediates yielded by this radical and a number of different products is formed. The formation of these products, both quantitatively and qualitatively has a strong dependence on the concentration of the OH- species and chloranil. The various possible routes of the hydrolysis are studied either spectrophotometrically or by E.S.R. Two different intermediates are observed absorbing at 426 nm and at 540 nm, respectively. Each species was formed and destroyed within 10 s to 30 min depending on the exact conditions. The reaction rate constants for the formation and the decay of the intermediates was estimated using the Guggenheim method. At both wavelengths the rate constants seem to have a complex relation to the concentration of the anion. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 385-391, 1997

Notes: Real-time kinetic measurements are reported for the Cl + CH3CO → CH2CO + HCl reaction. The experiments utilize infrared spectroscopy to determine the time dependence of the ketene formed via this reaction and of the CO produced from the subsequent rapid reaction between chlorine atoms and ketene. The reaction is investigated over a pressure range of 10-200 torr and a temperature range of 215-353 K. Within experimental error the rate constant under these conditions is k5a = (1.8 ± 0.5) × 10-10 cm3 s-1. We have also examined the Cl + CH2CO reaction and found it to have a rate constant of k6 = (2.5 ± 0.5) × 10-10 cm3 s-1 independent of temperature. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 421-429, 1997.

Notes: The relative rate technique has been used to measure the hydroxyl radical (OH) reaction rate constant of hexamethyldisiloxane (MM, (CH3)3Si-O-Si(CH3)3), octamethyltrisiloxane (MDM, (CH3)3Si-O-Si(CH3)2-O-Si(CH3)3), and decamethyltetrasiloxane (MD2M, (CH3)3Si-O-Si(CH3)2-O-Si(CH3)2-O-Si(Ch3)3). Hexamethyldisiloxane, octamethyltrisiloxane, and decamethyltetrasiloxane react with OH with bimolecular rate constants of 1.32 ± 0.05 × 10-12 cm3molecule-1s-1, 1.83 ± 0.09 × 10-12 cm3 molecule-1s-1, and 2.66 ± 0.13 × 10-12 cm3molecule-1s-1, respectively. Investigation of the OH + siloxane reaction products yielded trimethylsilanol, pentamethyldisiloxanol, heptamethyltetrasiloxanol, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, and other compounds. Several of these products have not been reported before because these siloxanes and the proposed reaction mechanisms yielding these products are complicated. Some unusual cyclic siloxane products were observed and their formation pathways are discussed in light of current understanding of siloxane atmospheric chemistry. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 445-451, 1997.

Notes: The reaction of H atoms with SiCl4 was studied behind reflected shock waves at temperatures between 1530 K and 1730 K and pressures around 1.5 bar by applying atomic resonance absorption spectroscopy (ARAS) for time resolved measurements of H atoms at the Lα-line. The thermal decomposition of a few ppm ethyl iodide (C2H5l) was used as a H-atom source. In the presence of a high excess of the molecular reactant SiCl4 a slow consumption of H was observed, which follows a pseudo-first-order rate law. Rate coefficient for the consumption of H by the reaction: \documentclass{article}\pagestyle{empty}\begin{document}$$ H+SiCl_4\,{\buildrel{k_1}\over{\longrightarrow}} SiCl_3\,+HCl \eqno(R1) $$\end{document} was determined to be: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1=1.4\times 10^{13}\exp(-4800 K/T) cm^3 mol^{-1} s^{-1}. $$\end{document} © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 469-472, 1997.

Notes: Mixtures of cyclopentadiene diluted with argon were used to investigate its decomposition pattern in a single pulse shock tube. The temperatures ranged from 1080 to 1550 K and pressures behind the shock were between 1.7-9.6 atm. The cyclopentadiene concentrations ranged from 0.5 to 2%. Gas-chromatographic analysis was used to determine the product distribution. The main products in order of abundance were acetylene, ethylene, methane, allene, propyne, butadiene, propylene, and benzene. The decomposition of cyclopentadiene was simulated with a kinetic scheme containing 44 species and 144 elementary reactions. This was later reduced to only 36 reactions. The ring opening process of the cyclopentadienyl radical was found to be the crucial step in the mechanism. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 505-514, 1997.

Notes: The temperature dependence of the rate coefficients for the OH radical reactions with iso-propyl acetate (k1), iso-butyl acetate (k2), sec-butyl acetate (k3), and tert-butyl acetate (k4) have been determined over the temperature range 253-372 K. The Arrhenius expressions obtained are: k1=(0.30±0.03)×10-12 exp[(770±52)/T]; k2=(109±0.14)×10-12 exp[(534±79)/T]; k3=(0.73±0.08)×10-12 exp[(640±62)/T]; and k4=(22.2±0.34)×10-12 exp[-(395±92)/T] (in units of cm3 molecule-1 s-1). At room temperature, the rate constants obtained (in units of 10-12 cm3 molecule-1 s-1) were as follows: iso-propyl acetate (3.77±0.29); iso-butyl acetate (6.33±0.52); sec-butyl acetate (6.04±0.58); and tert-butyl acetate (0.56±0.05). Our results are compared with the previous determinations and discussed in terms of structure-activity relationships. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet: 29: 683-688, 1997.

Notes: The processes of vibrational relaxation and unimolecular dissociation of the perfluoromethyl halides CF3Cl, CF3Br, and CF3I have been studied in the shock tube with the laser-schlieren technique. Vibrational relaxation was resolved in pure CF3Cl and CF3Br (400-484 K and 400-500 K, respectively), and in the mixtures; 2% CF3Cl/Kr (500-1000 K), 10% CF3Cl/Kr (440-670 K), 4% CF3Br/Kr (450-850 K), and 2% CF3I/Kr (620-860 K). Relaxation in the pure gases is extremely rapid, but shows a well-resolved, accurately exponential decay which provides very precise relaxation times in close agreement with ultrasonic results. Relaxation times as short as 0.1 μs-atm can be resolved, showing the method has a resolution within a factor 2-3 of the best ultrasonic methods. Relaxation dilute in rare gas shows a complex double exponential behavior consistent with a two-stage series process. Rates of CF3(SINGLEBOND)X fission in these mixtures were measured over 1800-3000 K, P〈0.55 atm, for CF3Cl; 1600-2500 K, P〈0.55 atm, in CF3Br; and 1260-2100 K, P〈0.34 atm, in CF3I. Rates for dissociation were derived from a full profile modeling using a secondary mechanism of six CF3 reactions. RRKM analysis showed all dissociations to lie near the low pressure limit. Using literature barriers, these rates are best fit with (ΔE)all=-270 cm-1 for CF3Cl, 〈ΔE〉down=0.3 T for CF3Br, and 〈ΔE〉down=800 cm-1 for CF3F. All these transfers are on the large side, similar to those found in other halogenated methanes. © 1997 John Wiley & Sons, Inc.

Notes: The sodium-hydrogen ion exchange constant for the system sodium 1-dodecanesulfonate-hydrochloric acid in aqueous acetonitrile has been determined from the pseudo-phase ion exchange model for surfactant catalytic effects. The results indicate that the micellar system behaves similarly for the aqueous and the aqueous acetonitrile (2.106 M) solvent systems.The influence of substrate molecular structure on micellar catalysis by perfluorooctanoic acid of the hydrolysis of hydroxamic acids (R - CO - NHOH) in aqueous acetonitrile has been explored. Data for substrate structures of fifteen compounds with R=alkyl, aralkyl, alicyclylalkyl, phenylalkyl, alkyl-substituted phenylalkyl, and with chain branching at the α, β, and γ positions are compared. Relative binding constant values indicate that substrates with aromatic groups are less well solubilized in the perfluoro micellar environment than are substrates with saturated groups.There is now evidence for specific micellar effects on the reaction rate as well as general micellar catalysis. © 1997 John Wiley & Sons, Inc.

Notes: The rate coefficient of the reaction CH+O2 → products was determined by measuring CH-radical concentration profiles in shock-heated 100-150 ppm ethane/1000 ppm O2 mixtures in Ar using cw, narrow-linewidth laser absorption at 431.131 nm. Comparing the measured CH concentration profiles to ones calculated using a detailed kinetics model, yielded the following average value for the rate coefficient independent of temperature over the range 2200-2600 K:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm{CH}+\rm{O}_{2}} = 10^{(13.99 \pm 0.12)} \hbox{ cm}^{3} \hbox{ mol}^{-1} \hbox{ s}^{-1} $$\end{document}The experimental conditions were chosen such that the calculated profiles were sensitive mainly to the reactions CH+O2 → products and CH3+M → CH+H2+M. For the methyl decomposition reaction channel, the following rate-coefficient expression provided the best fit of the measured CH profiles:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm{CH}_{3}+\rm{M}\rightarrow \rm{CH}+\rm{H}_{2}+\rm{M}} = 10^{(16.00 \pm 0.12)} \hbox{ exp($-$42900 K/\it T \rm) cm}^{3} \hbox{ mol}^{-1} \hbox{ s}^{-1} $$\end{document}Additionally, the rate coefficient of the reaction CH2+H→CH+ H2 was determined indirectly in the same system:\documentclass{article}\pagestyle{empty}\begin{document}$$ k_{\rm{CH}_{2}+\rm{H}} = 10^{14.15(+0.2,-0.6)} \hbox{ cm}^{3} \hbox{ mol}^{-1} \hbox{ s}^{-1} $$\end{document}© 1997 John Wiley & Sons, Inc.

Notes: A reaction mechanism for the photooxidation of dimethyldisulfide (DMDS) in aqueous acetonitrile has been established by kinetic modeling the UV absorbance vs. time curves under continuous irradiation. The model, built according to the known solution reactivity of oxysulfur radicals [1], consists of 22 steps involving 6 radical and 10 nonradical species. The first steps of the mechanism are the homolytic cleavage of the DMDS S - S bond with formation of methanethiyl radicals (CH3S·) followed by addition of these radicals to molecular oxygen. There are photoequilibria between thiyl (CH3S·), sulfinyl (CH3S·), and sulfonyl (CH3SO2·) radicals and the corresponding molecular species (methyl methanethiosulfinate CH3S(O)SCH3 or MMTSI, methyl methanethiosulfonate CH3S(O)2SCH3 or MMTS and meth-anesulfinic acid CH3S(O)OH or MSIA) which appear as long lived intermediates. Reactions of sulfonyl radicals with oxygen lead to methanesulfonic acid (CH3S(O)2OH) or MSA. Cleavage of sulfonyl radicals gives SO2 and CH3·, the parent compounds of sulfuric (H2SO4) and methanoic (HCOOH) acids. The predictive power of the model was tested at higher initial concentration of DMDS in anhydrous and aqueous acetonitrile. In these conditions, the proposed mechanism gives a semiquantitative description of the course of the reaction and reproduces the kinetic behavior of the long lived intermediates. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 825-834, 1997

Notes: The temperature dependence of the oxidation kinetics of Fe2+ by O3 at pH 0-3 was studied by stopped-flow technique in the temperature range 5-40°C. Activation parameters of the reactions involved in formation and decay of the ferryl ion (iron(IV)), FeO2+ are determined. The reaction of Fe2+ + FeO2+ was found to branch into two channels forming iron(III)-dimer, Fe(OH)2Fe4+, and Fe3+. The yield of the dimer, Fe(OH)2Fe4+, increases with temperature on the expense of the Fe3+ yield. On the basis of the overall rate constant and relative yield of Fe(OH)2Fe4+ the activation energy is determined for both channels. The activation parameters of the hydrolysis of the ferryl ion and its reaction with H2O2 were also determined. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 17-24, 1997.

Notes: The kinetics of oxidation of butane-2,3-diol by alkaline hexacyanoferrate (III), catalyzed by ruthenium trichloride has been studied spectrophotometrically. The reaction rate shows a zero-order dependence on oxidant, a first-order dependence on |Ru(III)|T, a Michaelis-Menten dependence on |diol|, and a variation complicated on |OH-|. A reaction mechanism involving the existence of two active especies of catalyst, Ru(OH)2+ and Ru(OH)3, is proposed. Each one of the active species of catalyst forms an intermediate complex with the substrate, which disproportionates in the rate determining step. The complex disproportionation involves a hydrogen atom transfer from the α C(SINGLE BOND)H of alcohol to the oxygen of hydroxo ligand of ruthenium, to give Ru(II) and an intermediate radical which is then further oxidized. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 1-7, 1997.

Notes: Heat capacity data between 298 and 1500K are used to derive a reduced set of apparent vibrational frequencies that can be used for estimation of molecular density of states, ρ(E). Estimates for a number of molecule and radical species, using a reduced set of three frequencies with noninteger degeneracies, are shown to compare favorably to direct count methods, which require specification of the complete frequency set. Use of the reduced set of three frequencies leads to significant improvement in calculations of ρ(E)/Q as compared to similar calculations which use only a single geometric- or arithmetic-mean frequency approximation. Since vapor phase heat capacity data of molecules and radicals can be estimated accurately by a group additivity formalism, this approach provides a method to estimate ρ(E) for use in calculations of pressure effects in unimolecular and chemical activation reaction systems. The accuracy of the ρ(E)/Q distributions obtained from heat capacity data makes this a viable method for those cases where the complete frequency distribution is not known. It is especially valuable for those cases where contributions to ρ(E) from internal rotors or low frequency vibrations such as inversions are not well known. This approach is useful for quantum RRK or inverse Laplace transform calculations of k(E) since no assignment of transition state properties is necessary. The reduced frequency set can also be combined with ΔHf(298) and S(298) to provide a compact data set to describe thermodynamic properties at any temperature. © 1997 John Wiley & Sons, Inc.

Notes: The kinetic study of the permanganic oxidation of some amino acids (glycine, L-alanine, L-α-amino-n-butyric acid, L-norvaline, and L-norleucine) has been carried out in buffered acid medium at 1 〈 pH 〈 3 using a spectrophotometric technique. An autocatalytic effect due to Mn2+ ions was found in all cases. The purpose of this work is to study the influence of the length of carbon chain of the above amino acids. For it, structural factors such as steric, inductive, and hyperconjugation effects of the carbon chain were analyzed. It was found that the reactivity of these compounds is not affected by only one factor, but the influence of several factors and the formation of intermediate complexes could be included in these oxidative processes. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 181-185, 1997.

Notes: Decomposition of the CF3CFHO radical formed in the reaction of CF3CFHO2 radicals with NO was studied at 296 and 393 K using a pulse radiolysis transient VIS-UV absorption absolute rate technique. At room temperature in 1 atmosphere of SF6 diluent it was found that the majority (79 ± 20)% of CF3CFHO radicals formed in the CF3CFHO2 + NO reaction decompose within 3 μs via C(SINGLE BOND)C bond scission. This result is discussed with respect to the current understanding of the atmospheric degradation of HFC-134a. As a part of the present work the rate constant ratio kCF3CFH+02/kCF3CFH+NO was determined to be 0.144 ± 0.029 in one atmosphere of SF6 diluent at 296 K. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 209-217, 1997.

Notes: The rate constants for the gas-phase reactions between methylethylether and hydroxyl radicals (OH) and methylethylether and chlorine atoms (Cl) have been determined over the temperature range 274-345 K using a relative rate technique. In this range the rate constants vary little with temperature and average values of kMEE+OH = (6.60-2.62+3.88) × 10-12 cm3 molecule-1 s-1 and kMEE+Cl= (34.9 ± 6.7) × 10-11 cm3 molecule-1 s-1 were obtained. The atmospheric lifetimes of methylethylether have been estimated with respect to removal by OH radicals and Cl atoms to be ca. 2 days and ca. 30-40 days, respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 231-236, 1997.

Notes: With potential-energy-surface parameters provided by Walch's calculations of the reaction path, we have calculated the thermal rate coefficient for the reaction, \documentclass{article}\pagestyle{empty}\begin{document}$$ CH+N_2 \longleftrightarrow HCN + N.\eqno(R1) $$\end{document} The theory employed assumes that the change in the reaction of the electron spin has little or no effect on the rate coefficient. The resulting expression for k1, \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 = 3.68 \times 10^7 {\rm T}^{{\rm 1}{\rm .42}} \exp ({{ - 20723} \mathord{\left/ {\vphantom {{ - 20723} {{\rm RT}}}} \right. \kern-\nulldelimiterspace} {{\rm RT}}}){{{\rm cm}^{\rm 3} } \mathord{\left/ {\vphantom {{{\rm cm}^{\rm 3} } {{\rm mole} - \sec }}} \right. \kern-\nulldelimiterspace} {{\rm mole} - \sec }} $$\end{document} in the temperature range, 1000 K ≤ T ≤ 4000 K, is in remarkably good agreement with the limited amount of experimental data available, suggesting that the assumption is valid. The origins of the “prompt-NO” phenomenon, our analysis of reaction (RI), and comparison of the results with experiment are all discussed in detail. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 253-259, 1997.

Notes: In the present investigation the non-RRKM behavior in the title reaction is quantified in two different ways: (1) Quasiclassical trajectory calculations of the thermal rate coefficient are compared with results from a microcanonical variational transition-state theory/RRKM model. Results on both the Varandas DMBE IV and Melius-Blint potentials indicate that the non-RRKM behavior acts to reduce the thermal rate coefficient by about a factor of two, independent of temperature from 250 K to 5500 K. The QCT thermal rate coefficients on the two potentials are in remarkably good agreement with experiment and with each other over the entire temperature range. (2) The non-RRKM behavior as a classical phenomenon is demonstrated and quantified on both potentials by a direct test of the fundamental assumption. Complex-forming classical trajectories, started as either O + OH or H + O2, are shown preferentially to return to the region of configuration space from which they were started. This test is discussed in detail in the text. The transition of the non-RRKM behavior from classical to quantum mechanics is also discussed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 275-287, 1997.

Notes: The kinetics of the gas-phase reactions of OH radicals, NO3 radicals, and O3 with indan, indene, fluorene, and 9,10-dihydroanthracene have been studied at 297 ± 2 K and atmospheric pressure of air. The rate constants, or upper limits thereof, for the O3 reactions were (in cm3 molecule-1 s-1 units): indan, 〈 3 × 10-19; indene, (1.7 ± 0.5) × 10-16, fluorene, 〈 2 × 10-19; and 9,10-dihydroanthracene, (9.0 ± 2.0) × 10-19. Using a relative rate method, the rate constants for the OH radical and NO3 radical reactions, respectively, were (in cm3 molecule-1 s-1 units): indan, (1.9 ± 0.5) × 10-11 and (6.6 ± 2.0) × 10-15; indene, (7.8 ± 2.0) × 10-11 and (4.1 ± 1.5) × 10-12; fluorene, (1.6 ± 0.5) × 10-11 and (3.5 ± 1.2) × 10-14; and 9,10-dihydroanthracene, (2.3 ± 0.6) × 10-11 and (1.2 ± 0.4) × 10-12. These kinetic data were used to assess the relative contributions of the various reaction pathways. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 299-309, 1997.

Notes: A differential method for analyzing first-order kinetic data is presented. While the essence of this approach has been known for almost a century, the use of computers to collect, store, and manipulate data has reenergized this innovative idea. Based on the equation ln |dA1/dt| = ln |k(Ao - A(infinity))| - kt, plots of ln |dAt/dt| vs. t were found to be lienar for both simulated kinetic data and data collected for the reaction of [(en)2Co(SCH2CH2NH2)]2+ with acrylamide. The rate constants for the reaction obtained by this method are identical to those obtained by the infinite-time method of analysis but do not require infinite-time measurements in their evaluation. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 333-338, 1997

Notes: The gas-phase reactivities of W(a5DJ, a7S3) with N2O, SO2, and NO in the temperature range of 295-573 K are reported. Tungsten atoms produced by the photodissociation of W(CO)6. The tungsten atoms were detected by a laser-induced fluorescence technique. The removal rate constants for the 6s25d4 a5Dl states were found to be pressure dependent for all of the reactants. Removal rate constants for the 6s15d5 a7S3 state were found to be fast compared to the a5DJ states and often approached the gas kinetic rate constant. The reaction rates for all the states were found to be pressure independent with respect to the total pressure. Results are discussed in terms of the different electronic configurations of the states of tungsten © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 367-375 1997

Notes: The initiation reaction of the thermal decomposition of silicon tetrachloride \documentclass{article}\pagestyle{empty}\begin{document}$$ SiCl_4\,+\,M\,{\buildrel{k_1}\over{\longrightarrow}} SiCl_3\,+Cl\,+M \eqno(R1) $$\end{document} was studied behind reflected shock waves at temperatures between 1550 K and 2370 K and pressures between 1 and 1.5 bar. Atomic resonance absorption spectrometry (ARAS) was applied for time-resolved measurements of H atoms at the Lα-line in SiCl4/H2/Ar systems. Additional experiments were performed in the SiCl4/Ar system following the absorption of SiCl4 at the Lα-line. Rate coefficients for the reaction (RI) were determined to be: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1=4.8\times 10^{16}\exp(-40954 K/T) cm^3 mol^{-1} s^{-1}. $$\end{document} The choice between two possible alternatives of the first decomposition step, namely elimination of either Cl2 or Cl, has been made in favor of the second reaction on the basis of kinetic and energetic considerations. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 415-420, 1997.

Notes: Principal component analysis, an advanced technique of sensitivity analysis, has been used to determine reduced mechanisms that can model species and temperature profiles in Plug Flow Reactors (PFR), Premixed Laminar Flames (PLF), and Perfectly Stirred Reactors (PSR) for two H2/air and two CH4/air mechanisms over a range of input parameters including initial temperature, equivalence ratio, and residence time. The results show that principal component analysis can be used effectively to reduce a comprehensive mechanism that contains unimportant reactions to a reduced mechanism that contains necessary and sufficient reactions. The accuracy of a reduced mechanism determined from principal component analysis can be easily controlled by carefully selecting reduction criteria. For the conditions chosen here, namely the requirement that radical profiles computed with reduced and comprehensive mechanisms agree to within 5%, substantial reductions were not achieved. Principal component analysis is able to resolve the influence of stoichiometry, combustor type, and mechanism on mechanism reduction.The two H2/air mechanisms were each reduced to mechanisms that can model all the cases considered, and the extent of reduction in each was very similar and modest. For H2/air chemistry, equivalence ratio had little effect on reduction. Combustor type was slightly more influential with the number of required reactions decreasing from PFR to PLF to PSR combustion. Relative to the H2/air system, principal component analysis of the CH4/air system is more difficult because of mechanism size. For CH4/air combustion, if we consider all equivalence ratios, PLFs require the most reactions, if individual equivalence ratios are examined, PFRs require the greatest number of reactions. Combustor type influences mechanism reduction substantially because of the different couplings between the fluid mechanics and chemistry. In H2/air combustion rich combustion required the fewest reactions and in CH4/air, it required the most. Reduction must be achieved by considering the entire mechanism since reactions interact in concert, for example, reactions unimportant in one CH4 mechanism are often important in the other. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 393-414, 1997.

Notes: Ozonolysis of cis- and trans-2-butene isomers were carried out in a 570 l spherical glass vessel in 730 torr synthetic air at 295 ± 3 K. The initial concentrations were 5 to 10 ppmv for the isomers and 2 to 5 ppmv for ozone. Quantitative yields were determined by FTIR spectroscopy for CH3CHO, HCHO, CH4, CH3OH, CO, and CO2. By means of computational subtraction of the spectral contribution of the identified products from the product spectra, residual spectra have been obtained. Formation of 2-butene ozonide, propene ozonide, and l-hydroperoxyethyl formate CH3CH(OOH)(SINGLE BOND)O(SINGLE BOND)CH(O) have been identified in the residual spectra. These products have been shown to be formed in the reactions of the Criegee intermediate CH3CHOO with CH3CHO, HCHO, and HCOOH, respectively. Mechanistic implications and atmospheric relevance of these observations are discussed. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 461-468, 1997.

Notes: The kinetics of oxidation of indigo carmine (IC) by N-sodio-N-bromotoluenesulfonamide or bromamine-T (BAT) in pH 5 buffer medium has been investigated at 30°C using spectrophotometry at 610 nm. The reaction rate shows dependencies of first-order on [IC]0 second-order on [BAT]0, fractional order on [H+], and inverse first-order on [ρ-toluenesulfonamide]. The addition of chloride and bromide ions, and the variation of ionic strength of the medium have no influence on the reaction rate. There is a negative effect of the dielectric constant of the solvent. Activation parameters have been calculated. A single-pathway mechanism for the reaction, consistent with the kinetic data, has been proposed. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 453-459, 1997

Notes: Relative rate coefficients for the reaction of acetyl (CH3CO) radicals with O2 (k4) and Cl2 (k7) have been obtained at 298 K and 228 K as a function of total pressure, using FTIR/environmental chamber techniques. Measured values of k4/k7 were placed on an absolute basis using k7=2.8×10-11 exp(-47/T) cm3 molec-1 s-1. At 298 K, the value of k4 is constant ((7±2)×10-13 cm3 molec-1 s-1) at pressures from 0.1 to 2 torr, then increases to a high pressure limiting value of (3.2±0.6)×10-12 cm3 molec-1 s-1, which is approached at pressures above 300 torr. At 228 K, the low-pressure value of k4 increases by about 20-30%, while the high pressure value remains unchanged. Experiments designed to elucidate the products of reaction (4) as a function of pressure at 298 K indicate that the reaction occurs via a concerted mechanism in which CH3CO radicals combine with O2 to give an excited acetylperoxy radical (CH3COO2*) which is increasingly stabilized at high pressure at the expense of a low pressure decomposition channel. The yield of acetylperoxy radicals from reaction (4) decreases from 〉95% at pressures above 100 torr, to about 90% at 60 torr, and 50% at 6 torr. Indirect evidence for formation of OH radicals from the low pressure decomposition is presented, although the carbon-containing coproduct(s) of this channel could not be identified. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 655-663, 1997.

Notes: Relative rate measurements using a reference compound with a well established rate constant are widely used for determining rate constants for gas-phase reactions. Linear least-squares regression is used to obtain the rate constant ratio, kA/kB, from the slope of plots of ln ([A]0/[A]t) vs. ln ([B]0/[B]t) where [A]0 and [B]0 are the initial concentrations of the reactant of interest, A, and of the reference compound, B, respectively, and the subscript “t” denotes the corresponding concentrations at time t. Linear least-squares analysis which does not take into account random errors in both [A] and [B] may lead to a small but systematic bias in the relative rate constant obtained from the slope of such plots. The magnitude of this bias was explored using Monte Carlo simulations. It is shown that although the bias is small for typical reaction conditions, of the order of a few percent, it can be of the same order of magnitude as the measured precision of most relative rate experiments. An algorithm for the analysis of such experiments which takes into account errors in both [A] and [B] and which avoids this systematic bias is discussed. © 1997 John Wiley & Sons, Inc.