摘要:

AbstractBoiling‐temperature measurements have been used to study the kinetics of the decomposition of urea. Values for the rate constants in neutral, acid, and basic media have been obtained and compared with literature data. The effect of the reverse reaction on the value of the experimental rate constants is discussed. The profile of the ebulliometric curves is different for the three media and is correlated with the number of various species present in solution. It is concluded that ebulliometric measurements can be useful for kinetic studie

ISSN:0538-8066    

DOI:10.1002/kin.550160702

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics and mechanism of the thermal decomposition ofn‐propylsilane have been studied by the single pulse shock tube‐comparative rate technique at pressures around 4700 torr between 1095–1240 K. The primary dissociation processes are 1,1 and 1,2 H2elimination with ø1,1⋍ 0.75 and ø1,2⋍ 0.25, respectively. Subsequent decompositions of the primary process product,n‐propylsilylene, to propylene and ethylene is complete even in the presence of excess butadiene. Possible mechanistic paths for these decompositions are discussed and an activation energy range of 30 ± 4 kcal is established for both processes. Induced decomposition via silylene chains accounts for 36–46% of the overall reaction in the uninhibited decomposition ofn‐propylsilane. The silylene chains are quenched in excess butadiene, and studies under maximum inhibition give overall decomposition kinetics of, logk(nPrSiD3, s−1) = 15.26–65,300 ± 1950 cal/2.303. Computer modeling results of the overall reaction both in the absence and presence of butadiene are also presented and shown to be in acceptable agreement with the ex

ISSN:0538-8066    

DOI:10.1002/kin.550160703

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractKinetics of hydrogen oxidation near the lower explosion limit in the kinetic region of chain termination has been studied. Major effects, causing deviations of the reaction kinetics from calculations by the linear theory of branched chain processes, are shown to be (1) the inhibition of the reacting mixture by the products of interaction of active centers with vacuum grease or with impurities contained in it and (2) the heterogeneous negative interaction of reaction active centers. The kinetics of hydrogen oxidation in this region has been calculated with consideration of the heterogeneous negative chain interaction. A set of parameters has been obtained that make it possible to determine by the shape of the kinetic curves the sign and the value of nonlinear interaction of chains near the lower explosion limit. It has been shown that the experimental data are in good agreement with the calculations, provided the heterogeneous negative chain interaction is taken into consideration and the inhibiting effect of impurities is eliminated. The rate of heterogeneous generation of chains on a quartz surface treated with hydrofluoric or boric acid has been determined.

ISSN:0538-8066    

DOI:10.1002/kin.550160704

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractChlorocyclopropane has been produced by addition of CH2(1A1) and CH2(3B1) to chloroethene. CH2was generated by the photolysis of ketene at 313 and 366 nm. Chlorocyclopropane was formed in a chemically activated state, had an energy content between 378 and 427 kJ/mol, and reacted in three parallel channels to 3‐chloropropene,cis‐ andtrans‐1‐chloropropene. As secondary reactions elimination of HCl from the chemically activated primary products occurred to form allene and propyne. The apparent rate constants for the isomerization and elimination reactions are reported. The results of RRKM calculations including distribution functions for the activated chlorocyclopropane and a stepladder model for the deactivation support the proposed reaction

ISSN:0538-8066    

DOI:10.1002/kin.550160705

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractAn efficient process for converting the energy stored in electronically excitedNF(a1Δ) into blue‐green BiF (AX) band emissions has been discovered. Bismuth atoms are converted to BiF and then repeatedly pumped to the (AO+) state in two steps via collisions with NF(a1Δ). A model has been formulated that predicts BiF emission intensities that are in excellent agreement with the observed values. Some of the rate coefficients required for this model are estimated by means of charge‐transfer theories. The cyclic nature of this system, along with its other basic properties, suggests that it has a strong potential to be an efficient blue‐green las

ISSN:0538-8066    

DOI:10.1002/kin.550160706

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe kinetics of OH reactions with furan (k1), thiophene (k2), and tetrahydrothiophene (k3), have been investigated over the temperature range 254–425 K. OH radicals were produced by flash photolysis of water vapor at λ>165 nm and detected by timeresolved resonance fluorescence spectroscopy. The following Arrhenius expressions adequately describe the measured rate constants as a function of temperature (units are cm3molecule−1S−1):k1= (1.33 ± 0.29) × 10−11exp[(333 ± 67)/T],k2= (3.20 ± 0.70) × 10−12exp[(325 ± 71)/T],k3= (1.13 ± 0.35) × 10−11exp[(166 ± 97)/T]. The results are compared with previous investigations and their implications regarding reaction mechanisms and atmospheric residenc

ISSN:0538-8066    

DOI:10.1002/kin.550160707

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractRelative rate constants for the reactions of hydroxyl radicals with a series of alkyl substituted olefins were measured by competitive reactions between pairs of olefins at 298 ± 2 K and 1 atmospheric pressure. Hydroxyl radicals were produced by the photolysis of H2O2with 254‐nm irradiation. The obtained rate constants were (× 10−11cm3molecule−1s−1): 2.53 ± 0.06, propylene; 5.49 ± 0.17,cis‐2‐butene; 5.47 ± 0.1, isobutene; 6.46 ± 0.13, 2‐methyl‐1‐butene; 6.37 ± 0.16,cis‐2‐pentene; 6.23 ± 0.1, 2‐methyl‐1‐pentene; 8.76 ± 0.14, 2‐methyl‐2‐pentene; 6.24 ± 0.08,trans‐4‐methyl‐2‐pentene; 10.3 ± 0.1, 2,3‐dimethyl‐2‐butene; 9.94 ± 0.1, 2,3‐dimethyl‐2‐pentene; 5.59 ± 0.07,trans‐4,4‐dimethyl‐2‐pentene. A trend in alkyl substituent effect on the rate constant was found, which is useful to pre

ISSN:0538-8066    

DOI:10.1002/kin.550160708

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractRate constants have been determined at 296 ± 2 K for the gas phase reaction of NO3radicals with a series of aromatics using a relative rate technique. The rate constants obtained (in cm3molecule−1s−1units) were: benzene,<2.3 × 10−17; toluene, (1.8 ± 1.0) × 10−17;oxylene, (1.1 ± 0.5) × 10−16;mxylene, (7.1 ± 3.4) × 10−17;pxylene, (1.4 ± 0.6) × 10−16; 1,2,3‐trimethylbenzene, (5,6 ± 2.6) × 10−16; 1,2,4‐trimethylbenzene (5.4 ‐ 2.5) × 10−16; 1,3,5‐trimethylbenzene, (2.4 ± 1.1) × 10−16; phenol, (2.1 ± 0.5) × 10−12; methoxybenzene, (5.0 ± 2.8) × 10−17;o‐cresol, (1.20 ± 0.34) × 10−11;m‐cresol, (9.2 ± 2.4) × 10−12;p‐cresol, (1.27 ± 0.36) × 10−11; and benzaldehyde, (1.13 ± 0.25) × 10−15. These kinetic data, together with, in the case of phenol, product data, suggest that these reactions proceed via H‐atom abstraction from the substituent groups. The magnitude of the rate constants for the hydroxy‐substituted aromatics indicates that the nighttime reaction of NO3radicals with these aromatics can be an important loss process for both NO3radicals and these organics, as

ISSN:0538-8066    

DOI:10.1002/kin.550160709

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe reactions of ground‐stateS(3PJ) atoms with thiirane, methylthiirane, andtrans‐2,3‐dimethylthiirane have been studied by flash photolysis‐VUV kinetic absorption spectroscopy. From the analysis of theS(3PJ) decay plots the following rate constants were determined: (1.4 ± 0.2) × 1013, (2.7 ± 0.3) × 1013and (4.0 ± 0.2) × 1013(in cm3mol−1s−1units) for thiirane, methylthiirane andtrans‐2,3‐dimethylthiirane, respectively, showing an upward trend with i

ISSN:0538-8066    

DOI:10.1002/kin.550160710

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY

摘要:

AbstractThe absolute rate constants for reversible addition of the substituted phenylthio radicals to vinylpyridines in solution at 23°C have been determined by flash photolysis method. For each phenylthio radical, the reactivities of vinylpyridines is 3–5 times lower than that of styrene. The relative equilibrium constants estimated with flash photolysis indicate that the stabilities of the adduct carbon‐centered radicals generated from vinylpyridines are similar to that from styrene. The Hammett plots suggest that the difference in the reactivities originates in the polar transition state; the nitrogen atom in 4‐vinylpyridine withdraws the electrons of vinylic doubl

ISSN:0538-8066    

DOI:10.1002/kin.550160711

出版商:John Wiley&Sons, Inc.    

年代:1984

数据来源: WILEY