摘要:

AbstractThe rate constants for reactions of OH with ClCH2CH2Cl, Cl2CHCHCl2, BrCH2CH2Br, CH3CH2Br have been measured by using a discharge flow‐resonance fluorescence (DF‐RF) technique over the temperature range 293–418 K. The rate constants as a function of temperature were fitted to the Arrhenius expression as follows: (k's units are 10−12cm3molecule−1s−1, and Ea's units are cal/mol)\documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{*{20}c} {{\rm OH} + {\rm ClCH}_2 {\rm CH}_2 {\rm Cl}:} & {k_1 = (8.91 \pm 1.63)^ \ast {\rm EXP}((-2164.5 \pm 119.9)/RT)}\\[10pt] {{\rm OH} + {\rm BrCH}_2 {\rm CH}_2 {\rm Br}:} & {k_2 = (14.36 \pm 2.70)^ \ast {\rm EXP}((- 2521.4 \pm 123.5)/RT)}\\[10pt] {{\rm OH} + {\rm Cl}_2 {\rm CHCHCl}_2:} & {k_3 = (5.01 \pm 0.89)^ \ast {\rm EXP}((- 1825.8 \pm 116.7)/RT)} \\[10pt] {{\rm OH} + {\rm CH}_3 {\rm CH}_2 {\rm Br}:} & {k_4 = (23.45 \pm 4.62)^ \ast {\rm EXP}((- 2558.2 \pm 124.1)/RT)}\end{array} $$\end{document}The experimental data have been compared with theoretical calculations of the semi‐empirical BEBO‐transition state method. Life‐times of the four haloethanes in the troposphere ha

ISSN:0538-8066    

DOI:10.1002/kin.550240102

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractStudies of the stoichiometry and kinetics of the reaction between hydroxylamine and iodine, previously studied in media below pH 3, have been extended to pH 5.5. The stoichiometry over the pH range 3.4–5.5 is 2NH2OH + 2I2= N2O + 4I−+ H2O + 4H+. Since the reaction is first‐order in [I2] + [I3−], the specific rate law,k0, isk0= (k1+k2/[H+]) {[NH3OH+]0/(1 + Kp[H+])} {1/(1 + KI[I−])}, where [NH3OH+]0is total initial hydroxylamine concentration, andk1,k2, Kp, and KIare (6.5 ± 0.6) × 105M−1s−1, (5.0 ± 0.5) s−1, 1 × 106M−1, and 725 M−1, respectively. A mechanism taking into account unprotonated hydroxylamine (NH2OH) and molecular iodine (I2) as reactive species, with intermediates NH2OI2−, HNO, N

ISSN:0538-8066    

DOI:10.1002/kin.550240103

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA kinetic study of the reactions I−+ S2O8=and CV++ OH−(CV = 4, 4′, 4″‐tris(dimethylamino)triphenylmethyl chloride or crystal violet) in different water in oil microemulsions is reported. The dependence of the rate constants on the nature of the surfactant as well as on the molar ratio R = [H2O]/[Surfactant]has been investigated. The results are interpreted on the basis of the electrostatic interactions between the reactants and the surfactant polar heads and considering the water properties inside the aqueous core of the

ISSN:0538-8066    

DOI:10.1002/kin.550240104

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe kinetic measurements in the Flash Vacuum Thermolysis (FVT) of 3,5‐Dimethyl‐ and 5‐Methyl‐ 4‐Nitroisoxazole confirm the already suggested intermediacy of the isomer 2H‐Azirine in the formation of 1‐ Cyano‐1‐Nitroacetone. Moreover, theoretical calculations of the stabilization energy (Es), at the transition state, using second order perturbation suggest that this azirine is formed through the isomer furoxan rather than directly from the s

ISSN:0538-8066    

DOI:10.1002/kin.550240105

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe oxidation kinetics of malachite green (MG) with peroxydisulphate ion (PDS) were investigated by monitoring the absorbance change at 618 nm, in aqueous solutions under buffered and unbuffered conditions. Under both conditions, the reaction had first order dependence on reductant and a fractional order (one half) dependence on the oxidant. The stoichiometric ratio between MG and PDS was 1:2. The reaction had a negative salt effect. Reaction rates were enhanced under both high or low pH relative to neutral conditions. A plausible mechanism is proposed.

ISSN:0538-8066    

DOI:10.1002/kin.550240106

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe equilibrium constant, Keqof the reaction NO2+ NO3+ M 2 N2O5+ M has been determined for a small range of temperatures around room temperature in air at 740 torr by direct spectroscopical measurements of NO2, NO3, and N2O5. At 298 K, Keqwas determined as (3.73 ± 0.61) × 10−11cm3molecule−1. Averaging this and 11 other independent evaluations of Keqyields Keq= (3.31 ± 0.82) × 10−11cm3molecule−1, where the uncertainty is given as one standard deviation. The kinetics of the O3/NO2/N2O5/NO3/ air system was studied in a static chamber at room temperature and 740 torr total pressure. Evidence of a unimolecular decay reaction of NO3, NO3→ NO + O2, was found and its rate coefficient was estimated as (1.6 ± 0.7) × 10

ISSN:0538-8066    

DOI:10.1002/kin.550240107

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractWe studied the formation and hydrolysis of the Schiff base of pyridoxal‐5′ ‐phosphate (PLP) andn‐dodecylamine (DOD) by kinetic methods and found the formation rate constants to be much larger than those reported for related systems. This can be ascribed to the occurrence of local concentration of charges in the vicinity of the carbinolamine, which stabilizes the corresponding transition state of the dehydration reaction. On the other hand, the hydrolysis rate constants of our system were considerably smaller as a result of the 12‐atom hydrocarbon chain acting as a bulky hydrophobic rest protecting the imine bond from attack

ISSN:0538-8066    

DOI:10.1002/kin.550240108

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractThe OH reaction with isoprene is studied. Methyl nitrite photolysis experiments were carried out in an outdoor smog chamber in an attempt to identify as completely as possible OH‐isoprene product distribution. Emphasis was placed on identification and quantification of oxygenated products. A Tenax‐based cryo‐trap thermal desorber used to trap, concentrate, and dry chamber samples for identification on a GC/MS is described. Analysis of the products revealed that O(3P) can form in reaction systems designed to study OH reactions that include high concentrations of NO, and consequently NO2, hence, this reaction is also examined. The yields of methacrolein and methyl vinyl ketone are determined as 25 ± 3 and 35.5 ± 4%, respectively, with an additional 4 ± 2% as 3‐methyl furan, totaling 65 ± 4%. These results, combined with those of previous studies allow 80% of isoprene's products to be explicitly identified, and the general structure of the remaining products to be ascertained. The O(3P) reaction produces 84 ± 8% epoxides, and 8 ± 3% species which result in production of HO2, and subsequently, OH. A heretofore unidentified product of the O(3P) reaction, 2‐methyl 2‐butenal, is identified. The rate constant of the NO2‐isoprene r

ISSN:0538-8066    

DOI:10.1002/kin.550240109

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

摘要:

AbstractA series of experiments have been performed to study the ozone‐isoprene reaction in a smog chamber by adding externally produced O3to the hydrocarbon in the dark. A chemical tracer, methyl cyclohexane, was added to probe the OH formation in the system. O(3P) formation was also examined using the known distribution of products that are unique to the O(3P)‐isoprene reaction (part I). The results provide clear evidence that both OH and O(3P) are produced by the O3‐isoprene reaction directly in large quantities; about 0.68 ± 0.15 and 0.45 ± 0.20 per O3‐isoprene reaction, respectively. These additional radicals severely complicate the analysis of the O3reaction, hence, computer kinetic modeling was necessary to ascertain the products of the O3reaction itself, corrected for OH and O(3P) reactions. The product distribution, which differs dramatically from that published previously, is: 67 ± 9% methacrolein, 26 ± 6% methyl vinyl ketone, and 7 ± 3% propene, accounting for 100 ± 10% of the reacted isoprene. Applicability of these results to the gas‐phase O3reaction with other unsaturated hydrocarbons is br

ISSN:0538-8066    

DOI:10.1002/kin.550240110

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550240101

出版商:John Wiley&Sons, Inc.    

年代:1992

数据来源: WILEY