摘要:

AbstractThe kinetics and mechanism of the silver(II) oxidation of methanol, ethanol, 1‐propanol, 1‐methyl‐ ethanol, 1‐butanol, 2‐methyl‐1‐propanol, 2‐butanol, 2‐methyl‐2‐propanol, D4‐methanol, and D6‐methanol have been investigated at 8.0 and 20.0°C in aqueous perchloric acid media (1.00 ≤ [HClO4] ≤ 4.00M; μ = 4.0M). The kinetics were monitored by following the disappearance of Ag(II) with a spectrophotometric stopped‐flow technique. The reactions are first order in each reactant and involve both Ag2+and AgOH+species. No kinetic or spectroscopic evidence for complex formation between reactants was obtained. The results are discussed with reference to electron density on the OH or αC‐H substrate sites and to the isotopic hydrogen/deuterium rate qu

ISSN:0538-8066    

DOI:10.1002/kin.550120502

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of the thermal reaction of mixtures of ethylene and cyclopentene has been examined for the occurrence of a concerted hydrogen‐transfer reaction,\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm C}_2 {\rm H}_4 + c - {\rm C}_5 {\rm H}_8 \to {\rm C}_2 {\rm H}_6 + c - {\rm C}_5 {\rm H}_6 $$\end{document}. The main products of the reaction were ethane and cyclopentadiene, and the rate of formation of ethane was first order in each reactant over a 2500‐fold change in the ratio of concentrations of the reactants. An increased surface‐to‐volume ratio of the reaction vessel or additions of oxygen and nitric oxide had little effect on the rate of formation of ethane, and it was concluded that the dominant reaction in the system was the concerted hydrogen‐transfer process. The rate constant for the reaction, measured over the temperature range of 325–505°C, was represented as\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k(1./{\rm mol}\,{\rm sec)}\, = \,12.0 - \frac{{49,700}}{{2.3RT}} $$\

ISSN:0538-8066    

DOI:10.1002/kin.550120503

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics of ethane oxidation was studied at 320, 340, 353 and 380°C, mixture composition 2 C2H6+ 1 O2, and total pressure 609 torr. It was found that at 320°C CH2O and CH3CHO were branching agents. A series of experiments was conducted on 2C2H6+ O2oxidation in the presence of 0.7%14C‐labeled ethylene. The ethylene oxide was found to form only from C2H4, formaldehyde formed from C2H4and C2H6; and CH3CHO, C2H5OH, and CH3OH formed only from ethane. The formation rates of C2H4, C2H4O, and CH2O were calculated by the kinetic tracer method. At 320°C the fraction of oxygen‐containing products formed from C2H4was 16–18%, and at 353 and 380°C it w

ISSN:0538-8066    

DOI:10.1002/kin.550120504

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe thermal unimolecular decomposition of bromocyclobutane has been investigated over the temperature range of 791–1224 K using the technique of very low‐pressure pyrolysis (VLPP). HBr elimination is the sole mode of decomposition under the experimental conditions. No evidence could be found for the ring‐cleavage pathway to ethylene and vinyl bromide. Assuming a four‐center transition state and an ArrheniusAfactor the same as that for HCl elimination from chlorocyclobutane, RRKM calculations show that the experimental unimolecular rate constants are consistent with the Arrhenius expression\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k(\,{\rm sec}^{{\rm - 1}} {\rm )}\, = \,(13.6 \pm 0.3) - (52.0 \pm 1.0)/{\rm \theta }\,$$\end{document}where θ = 2.303RTkcal/mol. The activation energy is higher than that for the open‐chain analog, 2bromobutane. This finding is consistent with the results for the corresponding chloro and io

ISSN:0538-8066    

DOI:10.1002/kin.550120505

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of ascorbic acid (DH2) oxidation have been studied under anaerobic conditions in the presence of Cu2+ions. At 10−4≤ [Cu2+]0<10−3M, 10−3≤ [DH2]0<10−2M, 10−2≤ [H2O2] ≤ 0.1M, 3 ≤ pH<4, the following expression for the initial rate of ascorbic acid oxidation was obtained:where χ2(25°C) = (6.5 ± 0.6) × 10−3sec−1. The effective activation energy is E2= 25 ± 1 kcal/mol. The chain mechanism of the reaction was established by addition of Cu+acceptors (allyl alcohol and acetonitrile). The rate of the catalytic reaction is related to the rate of Cu+initiation in the Cu2+reaction with ascorbic acid by the expressionwhereCis a function of pH and of H2O2concentration. The rate equationwherek1(25°C) = (5.3 ± 1) × 103M−1sec−1is true for the steady‐state catalytic reaction. The Cu+ion and a species, which undergoes acid–base and unimolecular conversions at the chain propagation step, are involved in quadratic chain termination. Ethanol and terbutanol do not affect the rate of the chain reaction at concentrations up to ≈0.3M. When the Cu2+–DH2–H2O2system is irradiated with UV light (λ = 313 nm), the rate of ascorbic acid oxidation increases by the value of the rate of the photochemical reaction in the absence of the catalyst. Hydroxyl radicals are not formed during the interaction of Cu+with H2O2, and the chain mechanism of catalytic oxidation of ascorbic acid is quantitatively described by the follo

ISSN:0538-8066    

DOI:10.1002/kin.550120506

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550120501

出版商:John Wiley&Sons, Inc.    

年代:1980

数据来源: WILEY