摘要:

AbstractThe gas phase elimination of 4‐(methylthio)‐1‐butyl acetate and 1‐chloro‐4‐(methylthio)‐butane has been investigated in a seasoned, static reaction vessel over the temperature range of 310–410°C and the pressure range of 46–193 Torr. The presence of the inhibitors propene, cyclohexene, and/or toluene had no effect on the rates. The reactions are homogeneous, unimolecular, and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius equations: for 4‐(methylthio)‐1‐butyl acetate, logk1(s−1) = (12.32 ± 0.29) − (192.1 ± 3.6) kJ/mol/2.303RT; for 1‐chloro‐4‐(methylthio)‐butane, logk1(s−1) = (12.23 ± 0.59) − (175.7 ± 6.8) kJ/mol/2.303RT. The CH3S substituent in 1‐chloro‐4‐(methylthio)‐butane has been found to participate in the elimination reaction, where tetrahydrothiophene and methyl chloride formation may result from an intimate ion‐pair type of mechanism. The yield of a cyclic product in gas phase reactions provides additional evidence of an intimate ion pair mechanism through neighboring group participation in g

ISSN:0538-8066    

DOI:10.1002/kin.550190802

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractA new, improved variant of the very low pressure reactor (VLPR) system with interchangeable discharge orifices was used for studying the compatibility of the chemical and physical processes occurring simultaneously. It is shown that the ratio of calculated and effective escape rate constants is a complex function of the reactor cell geometry for reactions of non‐spherical symmetry.The test reaction of atomic chlorine with methane proved to be a pure chemical process free of side reactions and was used to calibrate the system. The measured rate constant isk1= (0.993 ± 0.013) × 10‐13cm3/molec‐s at 25°C. A new procedure is outlined for measuring the equilibrium constant by changing the concentrations of all three components resulting in a remarkable accuracy ofK1= 1.406 ± 0.034 for the test reactio

ISSN:0538-8066    

DOI:10.1002/kin.550190803

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of pyruvic acid into carbon dioxide and acetaldehyde is a unimolecular first‐order reaction and takes place according to the rate equation, logk= 13.53–41,250/4.575 K. These parameters contrast markedly with those recently reported, viz. logk= 7.19–27,700/4.575 K and confirm that the latter, which gave an unacceptably low value for the frequency factor, are anomalous. The lower reactivity of pyruvic acid compared to oxalic acid is interpreted in terms of normal electronic ef

ISSN:0538-8066    

DOI:10.1002/kin.550190804

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe static system decomposition kinetics of disilane (\documentclass{article}\pagestyle{empty}\begin{document}${\rm Si}_{\rm 2} {\rm H}_{\rm 6} \mathop {\longrightarrow}\limits^1 {\rm SiH}_{\rm 2} + {\rm SiH}_{\rm 4}$\end{document}, 538–587 K and 10–500 Torr), are reported. Reaction rate constants are weakly pressure dependent, and best fits of the data are realized with RRKM fall‐off calculations using logA1,∞= 15.75 andE1,∞= 52,200 cal. These parameters yieldAHf0(SiH2)298= (63.5 −Eb, c) kcal mol,−1whereEb, cis the activation energy for the back reaction at 550 K,M= 1 std state. Five other silylene heat‐of‐formation values (ranging from 63.9 –Eb, cto 66.0 ‐Eb, ckcal mol−1) are deduced from the reported decomposition kinetics of trisilane and methyldisilane, and from the reported absolute and relative rate constants for silylene insertions into H2and SiH4. AssumingEb, c= 0, an average value of ΔHf0(SiH2) = 64.3 ± 0.3 kcal mol−1is obtained. Also, a recalculation of the activation energy for silylene insertion into H2, based in part on the new disilane decomposition Arrhenius parameters, gives (0.6 +Eb, c) kcal mol−1, in good agreement

ISSN:0538-8066    

DOI:10.1002/kin.550190805

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAbsolute rate constants for the gas phase reactions of OH radicals with ethane (k1), benzene (k2), fluorobenzene (k3), chlorobenzene (k4), bromobenzene (k5), iodobenzene (k6), and hexafluorobenzene (k7) have been measured over the temperature range 234–438 K using the flash photolysis resonance fluorescence technique. The rate constants measured at room temperature (296 K), at total pressures of argon diluent between 25 and 50 Torr, were (in units of 10−13cm3molecule−1s−1):k1= (2.30 ± 0.26),k2= (12.9 ± 1.4),k3= (6.31 ± 0.81),k4= (7.41 ± 0.94),k5= (9.15 ± 0.97),k6= (13.2 ± 1.6), andk7= (1.61 ± 0.24), respectively. The indicated errors are our estimate of 95% confidence limits and include two standard deviations from the least‐squares analysis together with an allowance for any possible systematic errors in the measurements. At elevated temperatures and under pseudo‐first‐order reaction conditions, non‐exponential hydroxyl radical decays were observed for benzene and the monosubstituted halo‐aromatics. For ethane and hexafluorobenzene, exponential decays were observed over the complete temperature range and the data were fit by the Arrhenius expressions:k1= (8.4 ± 3.1) × 10−12exp[(−1050 ± 100)/T] andk7= (1.3 ± 0.3) × 10−12exp[(−610 ± 80)/T], respectively. The results are compared with previous literature data and the

ISSN:0538-8066    

DOI:10.1002/kin.550190806

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe kinetics of the permanganate oxidation of formic acid in aqueous perchloric acid at 30°C were examined by the spectrophotometric method. The chemical reaction 2MnO 4−+ 3HCOOH + 2H+→ 2MnO2+ 3CO2+ 4H2O, appears to proceed via several parallel reactions. The overall rate equation has been obtained by using statistical multilinear regression analysis of the 660 cases studied, and the presence in the rate equation of two new terms in relation to previous studies shows that both permanganate autocatalytic effects and acid media inhibition must be taken into account when the reaction proceeds at constant ionic st

ISSN:0538-8066    

DOI:10.1002/kin.550190807

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe first‐order rate constants,k1, obtained for methanolysis and ethanolysis of phenyl salicylate (PSH) in aqueous mixed solvents, fit to a relationship:k1=A1· [ROH]T/(1 +A2[ROH]T) whereA1andA2are the unknown parameters and [ROH]Tis the total concentration of alkanol. It is proposed that the alkanolysis of PSH involves the preequilibrium formation of monomeric ROH from polymeric (ROH)n, followed by an intramolecular general base‐catalysed nucleophilic attack by monomeric ROH on the carbonyl carbon of the ester. In the mixed solvents containing alkanol and MeCN, thek1– [ROH]Tprofiles obtained in the presence of K+ions are different from those obtained in the presence of Na+ions which could be attributed to the cation‐induced changes in the alkanol structure. Negative KCl salt effect has been observed on methanolysis of PSH, while it is essentially unaffected by the presence of tetraalkylammonium iodide salts (R4NI). The rates of ethanolysis of PSH have been found to increase with increase in [R4NI] and this increase becomes more pronounced with increasing hydrophobic surface area of R4NI. The rate constants for methanolysis of PSH in aqueous mixed solvents containing 80% MeOH (v/v) are independent of [ŌH] within the [ŌH]range of 0.01 to 0.15 M. The rate of methanolysis could not be detected within ca. 47 h in mixed solvents containing 96% HeOH (3.8% MeCN and 0.2% H2O), 80% MeOH (19.8% MeCN and 0.2% H2O), and 0.022 M HCl. It is concluded that for efficient transesterification, PSH should exist in ionized form. The reaction of PSH with MeOH is ca. 400 times faster than that witht‐BuOH which could be ascribed to the most likely steric effect. The values of ΔH* and ΔS* obtained for methanolysis and ethanolysis are essentially independent of [ROH] within the ROH content of 20% to 96% for MeOH and 50% to 96% for EtOH. The effect of organic co‐solvent on rate of hydrolysis of PSH could be explained in terms of organic co‐solvent‐induce

ISSN:0538-8066    

DOI:10.1002/kin.550190808

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190809

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190810

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550190801

出版商:John Wiley&Sons, Inc.    

年代:1987

数据来源: WILEY