摘要:

AbstractThe kinetics of gamma‐radiation induced free radicals reactions in carbon tetrachloride solutions of cyclohexane, cyclooctane and cyclododecane were studied in the range of 27–190°C. The activation energies found were in the ordercC6H12>cC12H24>cC8H16, which was explained as due to their ring strain which has the same order. The following logk1was obtained using the known Arrhenius parameters for CCl3radical rec

ISSN:0538-8066    

DOI:10.1002/kin.550130602

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe decay of photochemically generatedtert‐butyl radicals in methylcyclopentane solutions containing chloroform is studied by time‐resolved ESR spectroscopy. In the pure solvent it perfectly follows the second‐order rate law for radical self‐termination. Increasing chloroform concentrations cause increasing admixture of a pseudo‐first‐order decay from which the rate constant of the title reaction is obtained. For 273 K ≦T≦ 323 K,\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm log}\,{\rm k(}M^{{\rm - 1}}\sec ^{ - 1}) = (8.41 \pm 0.14) - \frac{{8.12 \pm 0.18}}{\theta } $$\end{document}where θ = 2.303RTkcal/mol. CIDNP studies of the reaction mechanism and NMR product yields show H and Cl abstractions to occur with the temperature‐independent ratiokH/kCl= 1.4 ± 0.1. The results point to polar effects in the transfer reactions oftert‐butyl. The potential of time‐resolved ESR spectroscopy in studies of first‐ and pseudo‐first‐orde

ISSN:0538-8066    

DOI:10.1002/kin.550130603

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe photolysis of C2H5I in a glassy salt matrix (5M, 7.5M, 10M) of aqueous LiCl at 77 K with light of λ = 254 nm has been conducted, product analysis being by ESR and UV spectroscopy. The electrolytic medium causes the ionization of product HI, and I−concentrations can be continuously determined. During photolysis [I−] is less than the amount of C2H5I decomposed. But after photolysis thaw‐freeze cycling is accompanied by progressive growth in [I−] until the yield matches the C2H5I loss, the quantum yields being 0.26, 0.20, and 0.17 for the three LiCl solutions, respectively. The quantum yield of unionized HI is unchanged, however, at around 0.36, the overall change being due to a fall in the extent to which the HI is ionized in the direct photolysis (ø = 0.22, 0.16, and 0.11). It is proposed that this is a consequence of the density increase of matrix packing as the LiCl concentration is increased so that fewer HI are in contact with the aqueous medium and cage recombination is favored.The results establish that the primary reaction is essentially exclusive:and that substantial aggregates of C2H5I exist within which HI are caged and cannot be ionized. The direct reaction\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm C}_{\rm 2}{\rm H}_{\rm 5}{\rm I}+ h\nu \to {\rm C}_{\rm 2}{\rm H}_5^. + {\rm I}^. $$\end{document}occurs only to a trivial extent, ø; = 10−4, C2H5arising virtually totally via\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm C}_{\rm 2}{\rm H}_{\rm 4}+ {\rm H}^. \to {\rm C}_{\rm 2}{\rm H}_5^. $$\

ISSN:0538-8066    

DOI:10.1002/kin.550130604

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe mechanism of acid catalyzed decomposition of peroxodisulfate, (S2O 82−) in aqueous perchlorate medium involves the hydrolysis of the species H2S2O8and HS2O 8−and the homolysis of the species H2S2O8, HS2O 8−and S2O 82−at the OO bond. The overall rate law when 1.4M>[HClO4]>0.1Mis\documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{ - d[{\rm S}_{\rm 2}{\rm O}_8^{2 - }]}}{{dt}}\, = \,k_0 [{\rm S}_{\rm 2}{\rm O}_8^{2 - }]\, + \,k' [{\rm S}_{\rm 2}{\rm O}_8^{2 - }][{\rm H}+]\, + \,k{''}[{\rm S}_{\rm 2}{\rm O}_8^{2 - }][{\rm H}+]^2 $$\end{document}The constantsk′ andk″ contain the hydrolysis and homolysis rate constants of HS2O8−and H2S2O8, respectively. With added Ag(I), the acid catalyzed and Ag(I) catalyzed reactions take place independently. Ag(I) catalyzed decomposition appears to involve t

ISSN:0538-8066    

DOI:10.1002/kin.550130605

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractDetailed measurements on the kinetics and stoichiometry of the oxidation ofN‐methylformamide andN,N‐dimethylformamide by aquosilver (II) ions are reported. Four Ag aqIIions are consumed for each amide, and the reaction is first order in [Ag aqII] and first order in [amide]. The reaction is inversely dependent on acidity in the range of 1.5–5.0MHClO4. The oxidation rate is independent of [AgI] and ionic strength. The proposed reaction mechanism and activation parameters are compared with those found for the oxidation of amides by other oxidants such as cobalt(III) and manga

ISSN:0538-8066    

DOI:10.1002/kin.550130606

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractThe pyrolysis kinetics of 4,4‐dimethylpent‐2‐yl acetate, in a static system and in a vessel seasoned with allyl bromide, have been studied in the temperature range of 300–350°C and the pressure range of 48–211 torr. The olefin products were 4,4‐dimethylpent‐1‐ene,cis‐4,4‐dimethylpent‐2‐ene, andtrans‐4,4‐dimethylpent‐2‐ene. The rate coefficient for the homogeneous unimolecular elimination of this ester is given by the following Arrhenius equation: logk(sec−1) = (12.87 ± 0.31) − (181.2 ± 3.4)kJ/mol/2.303RT.The direction of elimination of this acetate has been found to proceed to the formation of the corresponding olefin by kinetic control. The present data, together with other pyrolysis work subject to kinetic control, imply that the direction of elimination of bulky alkyl esters is determined by steric hindrance in the eclipsedcisconformation. However, further analyses reveal that if a series of esters are compared, in the case of a gradual increase of alkyl branching when adjacent to a hydrogen atom (alkyl–H interactions), the rate was determined by steric acceleration, owing to the crowding effect at the highly substituted carbon atom. Otherwise if this gradual alkyl increase in size happened to be adjacent to another alkyl substituent (alkyl–alkyl interactions), the rate was affected by steri

ISSN:0538-8066    

DOI:10.1002/kin.550130607

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

摘要:

AbstractIt is shown thatAfactors for atom fissions in polyatomics can be reliably estimated by an improved version of the restricted free rotor model (RFRM). No adjustable parameters are used in the evaluation ofAfactors for the dissociation of the ROF bond (R: NO2, SF5, CF3, FSO2), and the authors' predictions are compared with high‐pressure kinetic data for these reactions. In the case of O2NOF, for which full spectroscopic information is available, RFRM reproduces the observed valueAmwell within a factor of 2. Similar agreement is reached for F5SOF and FO2SOF, assigning reasonable limits to their OF torsional frequencies. For F3COF,Amandthe calculated back reaction rate constant, which is independent of the model, are both much too small to be plausible, suggesting falloff effects rather than a failure of

ISSN:0538-8066    

DOI:10.1002/kin.550130608

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY

ISSN:0538-8066    

DOI:10.1002/kin.550130601

出版商:John Wiley&Sons, Inc.    

年代:1981

数据来源: WILEY