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  • 1995-1999  (241)
  • 1995  (241)
  • Physical Chemistry  (241)
  • Nuclear reactions
  • 101
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 445-451 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The origin of the π-facial selectivity in nucleophilic additions to cyclohexanone was analysed by means of ab initio MO calculations (MP2/6-31G*//HF/6-31G*). The calculations showed that BH3 attacks at the axial side whereas MeLi attacks at the equatorial side. Calculated kinetic and equilibrium deuterium isotope effects and the structures of the transition states (TSs) demonstrated that four factors, stabilization of the axial TS by antiperiplanar allylic bonds, destabilization of the equatorial TS by torsional strain, destabilization of the axial TS by steric hindrance between a nucleophile and the 3,5-axial hydrogens and destabilization due to the conformational deformation of the ring in both the equatorial and axial TSs, operate in the same direction and can bring about the apparent selectivity changeover. The magnitudes of anti-D KIEs for the MeLi and the EtLi additions to acetone were consistent with the Anh-Eisenstein model rather than the Cieplak model.
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  • 102
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 435-441 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ring proton affinities (PAs) in fluorobenzene and toluene were examined by the MP2(fc)/6-31G**//HF/6-31G* + ZPE(HF/6-31G*) model. The calculated PAs are in good accordance with the available experimental evidence, their order being PA(p) 〉 PA(o) 〉 PA(m) 〉 PA(i), where p, o, m and i stand for para, ortho, meta and ipso positions, respectively. The relative values of the proton affinities can be interpreted in terms of the ground-state charge distribution (initial state effect) and the characteristic π-bond fixation produced by protonation (final state effect). The influence of the latter is either concerted with the initial charge distribution leading to higher PAs (ortho and para positions) or disconcerted as in meta protonation, which has a lower PA value. Finally, it is shown that PAs in difluorobenzenes and fluorotoluenes are additive and can be reduced to the characteristic PAs of fluorobenzene and toluene with good accuracy.
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  • 103
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1,3-Dipolar cycloadditions of N-(phenylmethylene)benzenesulphonamide with mesionic N-methyl-1,3-oxazolium-5-olates give 2,5-disubstituted imidazole derivatives with high regioselectivity. The intermolecular interactions underlying this regioselectivity were investigated. The conformational and electronic properties of the reagents were characterized separately. The approach in the early stages of the reactions was then modelled by considering the steric and electrostatic molecular interactions. The interaction energies related to different reaction paths were calculated by perturbation molecular orbital (PMO) treatment and compared.
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  • 104
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 463-467 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1H and 13C NMR data for 2-diethylaminomethyl-3,4,6-tri- and -tetrachlorophenols in CH2Cl2 solutions at a variety of temperatures are reported. The results are consistent with intramolecular hydrogen bonding and proton transfer as shown in the structure 3. Concentration dependence of the NMR data for the perchloro compound shows an additional hydrogen bonding process attributed to the solute self-association. The 1H, 13C and 15N NMR data support the proposed proton transfer structure.
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  • 105
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 468-472 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The normal electron-demand Diels-Alder cycloaddition between cyclopentadiene and methyl vinyl ketone is inhibited by the cycloadduct, when catalyzed by kaolinite-supported zinc chloride. This inhibition stems from occupation of the catalytic sites by both the cycloadduct and methyl vinyl ketone. Catalysis occurs in this case exclusively by a decrease in the enthalpy of activation.
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  • 106
    Electronic Resource
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 473-483 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ab initio studies on the SN2 identity exchange reactions RCH2X + X- → X- + RCH2X for R = CH2CH with X- = H, NH2, OH, F, PH2, SH and Cl, and for R = CH3 and CH≡C with X- = Cl were carried out at the HF and MP2 levels using the 6-31 ++ G** basis sets. The activation barriers, ΔE≠, and major structural changes, Δd≠ (C-X), in the activation process are closely related to the electronegativity of the R and X groups. The effect of electronegativity is twofold: a stronger electronegativity of R and/or X leads to a lesser electronic as well as structural reorganization required in the activation and to a greater correlation energy in the transition state. The former effect lowers the energy barriers at both the HF and MP2 levels whereas the latter lowers only the correlated (MP2) activation energies. Results with R = CH2CH, as a model for R = C6H5, indicate that ‘benzylic effect’ arises mainly from the relatively stronger electron acceptor ability of the phenyl group.
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  • 107
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 484-489 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The fluorescence of some aliphatic diamines was studied in the gas phase and in some solvents at several temperatures. It was found that N,N,N′,N′-tetramethylpropane-1,3-diamine (TMPD) and N,N,N′,N′-tetramethylbutane-1,4-diamine (TMBD) have two emission bands in the gas phase. TMBD also shows two bands in solution. These bands were assigned previously to an excited monomer and an intramolecular excimer. From the temperature dependence of the intensity ratio of the two bands, the enthalpy changes for the excimer formation were evaluated. The stability of the cyclic excimer is discussed in terms of the ring size effect and the solvent effect on the band positions.
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  • 108
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 490-495 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The pKBH+ values of the conjugate acids of N-phenylhydroxylamines change drastically when the pKBH+ values are determined in dimethyl sulfoxide (DMSO) rather than methanol. The Hammett ρ values change from -5·69 to -1·20 on going from methanol to DMSO for protonated N-phenylhydroxylamines, in contrast to a shift of -4·70 to -4·83 for protonated N-methylanilines in the same two solvents. This large change in susceptibility indicates that the species from which the proton departs is not the same for protonated N-phenylhydroxylamines in the two solvents. Experimental and computational evidence supports ionization of the H+ from the O atom for the protonated N-phenylhydroxylamines in DMSO.
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  • 109
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 496-505 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Molecular reactivity parameters based on the concept of an effective electronic potential and defined as a simple function of the molecular charge distribution were applied in a study of various aspects of the chemical reactivity of azabenzenes and azanaphthalenes. Excellent linear correlations were obtained for proton affinities, pKa values, H-D exchange rate exponents and 13C shifts induced by the paramagnetic shift reagent TEMPO. In the last case, the predictions for quinazoline prompted a reinvestigation of the 13C NMR spectrum of this compound, resulting in a reassignment of the spectrum relative to the assignment assumed by Grant and co-workers.
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  • 110
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 111
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 507-528 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: An empirical MM2 force-field was developed for the calculation of steric or strain energies of carbenium ions, and applied to the rationalization of the rates of solvolysis of bridgehead derivatives. The latter constitute a homogeneous series of model compounds for solvolysis, spanning a rate range of ca 20 log units. Their rate constants correlate with the calculated steric energy differences between bridgehead bromides and the corresponding carbenium ions. The rate constants of tertiary derivatives of general structure may similarly be rationalized in terms of strain changes, although the correlation exhibits more scatter than that for the bridgehead derivatives alone. In the bridgehead series, the relative free energies of activation for solvolysis correlate with the heterolytic bond dissociation energies D° (R+ - Br-) in the gas phase. However, this correlation breaks down when simple mono- and acyclic substrates are included. This is attributed in part to the proximity of the leaving group in the transition state of solvolysis, which stabilizes the developing positive charge at the cationic centre in comparison with the charge of the free ion. The significance of the force-field calculations with respect to the structure of bridgehead carbenium ions was tested by comparison of structural data obtained from ab initio calculations. The structures of cations suffering strong distortions owing to C-C hyperconjugation are poorly reproduced by the molecular mechanics calculations, the parameters of which are based on solvolytic reactivity and not on carbenium ions.
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  • 112
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 113
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 552-558 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Rates of acid-catalysed hydrolysis of phenyldiazoacetic acid were measured in aqueous solution at 25°C across the entire acidity range pCH+ = 1-13. The reaction was found to occur through both the non-ionized and inonized forms of the substrate, with the ionized form reacting faster by a factor of 650. Appreciable solvent isotope effects in the normal direction (kH/kD 〉 1) and the occurrence of general acid analysis show that hydrolysis occurs by rate-determining proton transfer to the diazocarbon atom of the substrate. Analysis of the rate profile for the reaction provides an estimate of the acidity constant of phenyldiazoacetic acid, pKa = 3·70, which is apparently the first determination of the acid strength of an α-diazocarboxylic acid. Comparison of this result with the pKa of phenylacetic acid shows the diazo group to have a mild (4×) acid-strengthening effect, whose modest magnitude is attributed to opposing resonance and polar effects.
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  • 114
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 559-562 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The monocation-dication equilibria of 6-nitro and 6-sulphonic acid derivatives of betacarboline (9H-pyrido[3,4-b]indole) were investigated mostly by UV-visible absorption spectroscopy. Dications are formed in very highly concentrated sulphuric acid solutions (〉15 M). Ionization constants, pKa values and solvation parameters obtained from the excess acidity method are reported. The unusually high m* parameters are discussed and compared with other related data.
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  • 115
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 610-616 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aminolysis and hydrolysis of several sulphamate esters, RNHSO2ONp (R = PhCH2, Ph, 4-MeC6H44, 3-MeC6H4, 4-FC6H4, 4-ClC6H4, 3-ClC6H4, H; Np = 4-NO2C6H4) were been studied in 50% (v/v) aqueous acetonitrile at various temperatures. Reaction of the esters with an amine (R1NH2) gives -ONp and both sulphamide, (RNHSO2NHR1) and sulphamate (RNHSO2O-R1NH3+) products. First-order rates were determined by the appearance of -ONp and sometimes also by the disapperance of ester. The reaction was found to be independent of amine type and concentration and at the high pHs that obtain the substrate esters are fully ionized. A Hammett ρacyl of -;1·8 was obtained for the decomposition of the sulphamate anions and this is consistent with substantial N=S bonding in the transition state leading to N-sulphonylamine, RN=SO2. This intermediate then partitions very rapidly, reacting with R1NH2 and H2O respectively. ΔH
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  • 116
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 117
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 689-695 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1H, 13C and 15N NMR data for nitraminopyridines are discussed in terms of tautomeric equilibria in these compounds. The favoured tautomer is determined mainly from 15N NMR spectroscopy. The chemical shift of the nitrogen atom of the nitro group in nitraminopyridines and N-nitroanilines which cannot tautomerize vary from 28·0 to 35·4 ppm in DMSO solution. 3-Nitraminopyridine and 2-nitramino-3- and -5-nitropyridines behave similarly. In the 15N NMR spectra of nitrimino-1-methyldihydropyridines, used as models, an upfield shift of that atom, different from that observed for 2-nitraminopyridine, indicates the significance of the nitrimino tautomer. In contrast, a downfield shift of the ring nitrogen atom of some other compounds shows an increased weight of the nitramino tautomer. 3-Nitraminopyridine, when dissolved in DMSO, does not have the zwitterionic structure. Changes in the chemical shift of the amino nitrogen atom are not readily interpreted. Some proton and carbon chemical shifts and hydrogen-hydrogen and carbon-hydrogen spin-spin coupling constants can also be used to determine the predominant tautomer of 2- and 4-nitraminopyridines.
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  • 118
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    Journal of Physical Organic Chemistry 8 (1995), S. 699-705 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Irradiation of 1-(p-nitrophenyl)-5,5-dimethyl-1,3-hexadiyne (NDHD) in aqueous sulfuric acid yields conjugated allenyl ketones (1 and 2) and β-dicarbonyl compounds (3 and 4). The products 1 and 2 are primary photoproducts while 3 and 4 are secondary products formed by thermal hydration of the primary photoproducts showing the maximum quantum yield at H0 = -1·0. A mechanism involving a synchronous addition of hydronium ion (H3O+) to a triplet state of NDHD is proposed.
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  • 119
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The equilibrium constant, Kan(H2CO), for the formation of α-aminoacetonitrile from formaldehyde, ammonia and hydrogen cyanide was evaluated at 25°C. A first estimation of Kan(H2CO) was obtained from extrathermodynamic relationships of the type log K′ vs ∑σ*. The final value was then obtained from a comparison of the experimental and calculated pH dependences of α-hydroxy- and α-aminoacetonitrile concentrations. From these results, it appears that, after equilibrium, the ratio between the concentrations of the two precursors glycine and hydroxyethanoic acid, is a linear function of the concentration of free ammonia, i.e. [CH2(OH)CN] [CH2(NH2)CN] = 21 [NH3] at 25°C.
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  • 120
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Proton transfer processes in both the ground and excited states in anils of aromatic α-hydroxyaldehydes (salicylaldehyde, 2-hydroxynaphthalene-1-carbaldehyde and the novel 10-hydroxyphenanthrene-9-carbaldehyde) have been studied by a combination of spectroscopic techniques. Solution 1H and 13C NMR is used to establish the position of the tautomeric equilibria. UV-visible absorption and fluorescence spectral data help to characterize the existence, in all cases, of excited-state intramolecular proton transfer (ESIPT) pheonmena. Semi-empirical calculations involving full geometry optimization and calculation of heats of formation for the ground state (AM1) and vertical excitation energies and oscillator strengths (INDO/S) are in agreement with the experimental observations.
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  • 121
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995) 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 122
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    Chichester : Wiley-Blackwell
    Journal of Physical Organic Chemistry 8 (1995), S. 761-773 
    ISSN: 0894-3230
    Keywords: Organic Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Chiral polymethine dyes constitute a particular class of conjugated π systems. Artificial chiral polymethine dyes were first synthesized by König and Langbein in 1928 in order to clarify the electronic structure of cyanine dyes; some natural dyes such as musca-aurin I (from the toadstool fly agaric) and betanin (from the vegetable red beets) are known to be chiral pentamethinium cyanine dyes, the chirality of which stems from L-α-amino acids as end-groups. The reasons why chiral polymethine dyes are not only of historical interest but once again the subject of research are explained.
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  • 123
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    International Journal of Chemical Kinetics 27 (1995), S. 73-84 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The isoconversional method was used to elucidate the kinetics of reversible solid-state reactions occurring under nonisothermal linear heating. The characteristic dependencies of the effective activation energy (E) on the extent of conversion (W) were established for two model processes: a reversible first-order reaction and a reversible reaction followed by an irreversible one. For the first process, E is almost independent of W and varies between the activation energy of the direct and inverse reaction. For the second, process with an endothermic reversible step, the dependence of E on W is of decreasing shape. The effective activation energy is limited by the sum of the activation energy of the irreversible reaction and the enthalpy of the reversible reaction, at low conversions, and by the activation energy of the irreversible reaction at high conversions. Analyses of the kinetic data for the dehydration of crystalhydrates, as well as other processes proceeding through a reversible step, show the dependencies of E on W characteristic of a reversible reaction followed by an irreversible one. © 1995 John Wiley & Sons, Inc.
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  • 124
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    International Journal of Chemical Kinetics 27 (1995), S. 49-57 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of secondary alicyclic amines with the title substrate (PDTC) are subjected to a kinetic study in 44 wt.% aqueous ethanol, 25.0°C, ionic strength 0.2 M (KCl). Pseudo-first-order rate coefficients (kobs) are found under amine excess. Linear plots of [N]/kobs against 1/[N], where N is the free amine, are obtained for the reactions with piperidine, piperazine, 1-(2-hydroxyethyl)piperazine, and morpholine. The reaction with 1-formylpiperazine exhibits a linear plot of kobs against [N]2. These results are interpreted through a mechanism consisting of two tetrahedral intermediates: a zwitterionic (T±) and an anionic (T-), where the amine catalyzed proton transfer from T± to T- is partially rate determining for the four former reactions and is fully rate determining for the reaction of 1-formylpiperazine. The rate microcoefficients involved in the reaction scheme are either determined experimentally or estimated. Comparison with the corresponding microcoefficients reported for the same reactions in water reveals that the rate coefficient for formation of T± from reactants (k1) is smaller and that for the reversal of this (k-1) is larger in aqueous ethanol compared to water, in agreement with the expected structure of the corresponding transition state.Bronsted-type plots are obtained for k1, k-1, and K1 (=k1/k-1) with slopes ca. 0.4, -0.6, and 1.0, respectively. Comparison of the present stepwise reactions with the concerted ones found in the same aminolysis of O-ethyl 2,4,6,-(trinitrophenyl) dithiocarbonate indicates that T± is so destabilized by the change of PhS by the 2,4,6-trinitrobenzenethio group that T± no longer exists and becomes a transition state. © 1995 John Wiley & Sons, Inc.
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  • 125
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    International Journal of Chemical Kinetics 27 (1995), S. 89-97 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the solvolysis of Co(4-t-Bupy)4Cl2- ions in water + methanol and water + ethanol, log (rate constant) does not vary linearly with the reciprocal of the dielectric constant. The Gibbs free energy, the enthalpy, and the entropy of activation are insensitive to changes in the solvent composition in these mixtures, although a slight broad maximum in ΔH* and ΔS* probably exists at mole fractions of about 0.2 in water + ethanol. This contrasts with the extrema in ΔH* and ΔS* found with more hydrophobic alcohols used as cosolvents. However, the application of a Gibbs energy cycle to the solvolysis in water and in the mixtures shows that there is a differential effect of changes in solvent structure on the emergent solvated CoIII cation in the transition state and on Co(4-t-Bupy)4Cl2+ in the initial state. The stability of the former increases relative to that of the latter as the cosolvent content of the mixture rises. © 1995 John Wiley & Sons, Inc.
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  • 126
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    International Journal of Chemical Kinetics 27 (1995), S. 109-122 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A kinetic study has been carried out on the oxidation of N, N, N′, N′,-tetraethyl-p-phenylenediamine (TEPD) by metal ion like Ce4+, oxoanions viz., MnO4- and Cr2O72-; peroxides such as peroxomonosulphate (PMS), peroxodisulphate (PDS), and H2O2; and halogens namely Cl2, Br2, and I2. The fast kinetics of the formation and decay of the radical cation TEPD·+ have been analyzed at 565 nm by the stopped-flow technique under pseudo-first-order conditions. From the kinetic data, it has been inferred that the reactions were found to be of first-order with respect to [TEPD] and [oxidant] but over all it has been of second-order. The observed second-order rate constants in both the formation and decay of TEPD·+ has been correlated with the oxidation potentials of the various oxidants employed in this study. The effect of pH on the oxidation has been investigated in the formation and decay of TEPD·+ as well as reduction studies have also been carried out using dithionite which has been found to regenerate the TEPD from the TEPD·+ and the corresponding rate constant has also been determined. Besides these, this article also explains how the TEPD, which forms TEPD·+ acts as a better electron relay than TMPD(N, N, N′, N′-tetramethyl-p-phenylenediamine) which forms TMPD·+, even though both of them undergo one-electron oxidation and are used in the chemical routes to solar energy conversions. The observed rate constants for electron transfer were correlated theoretically using Marcus theory. The observed and calculated rate constants have good correlation. © 1995 John Wiley & Sons, Inc.
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  • 127
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    International Journal of Chemical Kinetics 27 (1995), S. 181-188 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Laser flash photolysis (at 248 or 308 nm) or aryl iodides in water or water/methanol solutions produces iodine atoms and phenyl radicals. Iodine atoms react rapidly with added I- to form I2- but do not react rapidly with O2 (k ≤ 107 L mol-1 s-1). Iodine atoms oxidize phenols to phenoxyl radicals, with rate constants that vary from 1.6 × 107 L mol-1 s-1 for phenol to about 6 × 109 L mol-1 s-1 for 4-methoxyphenol and hydroquinone. Ascorbate and a Vitamin E analogue are also oxidized very rapidly. N-Methylindole is oxidized by I atoms to its radical cation with a diffusion-controlled rate constant, 1.9 × 1010 L mol-1 s-1. Iodine atoms also oxidize sulfite and ferrocyanide ions rapidly but do not add to double bonds. The phenyl radicals, produced along with the I atoms, react with O2 to give phenylperoxyl radicals, which react with phenols much more slowly than I atoms. © 1995 John Wiley & Sons, Inc.
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  • 128
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    International Journal of Chemical Kinetics 27 (1995), S. 197-201 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 129
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    International Journal of Chemical Kinetics 27 (1995), S. 205-218 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the gas-phase reaction of Cl atoms with CF3I have been studied relative to the reaction of Cl atoms with CH4 over the temperature range 271-363 K. Using k(Cl + CH4) = 9.6 × 10-12 exp(-2680/RT) cm3 molecule-1 s-1, we derive k(Cl + CF3I) = 6.25 × 10-11 exp(-2970/RT) in which Ea has units of cal mol-1. CF3 radicals are produced from the reaction of Cl with CF3I in a yield which was indistinguishable from 100%. Other relative rate constant ratios measured at 296 K during these experiments were k(Cl + C2F5I)/k(Cl + CF3I) = 11.0 ± 0.6 and k(Cl + C2F5I)/k(Cl + C2H5Cl) = 0.49 ± 0.02. The reaction of CF3 radicals with Cl2 was studied relative to that with O2 at pressures from 4 to 700 torr of N2 diluent. By using the published absolute rate constants for k(CF3 + O2) at 1-10 torr to calibrate the pressure dependence of these relative rate constants, values of the low- and high-pressure limiting rate constants have been determined at 296 K using a Troe expression: k0(CF3 + O2) = (4.8 ± 1.2) × 10-29 cm6 molecule-2 s-1; k∞(CF3 + O2) = (3.95 ± 0.25) × 10-12 cm3 molecule-1 s-1; Fc = 0.46. The value of the rate constant k(CF3 + Cl2) was determined to be (3.5 ± 0.4) × 10-14 cm3 molecule-1 s-1 at 296 K. The reaction of Cl atoms with CF3I is a convenient way to prepare CF3 radicals for laboratory study. © 1995 John Wiley & Sons, Inc.
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  • 130
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    International Journal of Chemical Kinetics 27 (1995), S. 153-165 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and mechanism of ozone reactions with aliphatic ethers in CCl4 solution have been investigated with a set of six symmetrical ethers: ethyl, chloroethyl, iso-propyl, n-butyl, iso-amyl, and n-amyl. The corresponding kinetic constants at ambient temperature are 3.1, 0.035, 5.4, 6.3, 6.8, and 7.8 1/(mol s). Upon ozonation of n-butylether the main products are butylalcohol, butylaldehyde (butyric acid), and butylbutyrate. A common precursor of these products is the α-hydrotrioxybutylether. Experimental values of the preexponential factors are compared with those calculated according to the activation complex theory with linear or cyclic form of the activated complex. The cyclic form of the activated complexes is unfavorable because of the kinetic factor. Abstraction of hydrogen atom or the far less probable hydride ion abstraction from α-position in the ether molecules is the rate-determining step of ozonation. The rate-determining factors are the electron density and geometry of the reaction center and the energy of the α-C—H bonds. © 1995 John Wiley & Sons, Inc.
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  • 131
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    International Journal of Chemical Kinetics 27 (1995), S. 195-196 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The author pointed out that hydrolysis of acetonitrile, trace impurity of someorganic solvents, and insolubility of benzene can make great effects on B-Z or B-R oscillators in aqueous-organic mixed media. And surfactant is better than organic solvent in the design of chemical oscillators with insoluble substance as substrate. © 1995 John Wiley & Sons, Inc.
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  • 132
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    International Journal of Chemical Kinetics 27 (1995), S. 189-194 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using a relative rate technique the reactions of fluorine and chlorine atoms with CF3COOH have been determined to proceed with rate constants of (5.6 ± 0.7) × 10-11 and 〈1 × 10-17 cm3 molecule-1 s-1, respectively. Quoted errors for the F atom rate constant reflect statistical uncertainty (two standard deviations). Systematic errors could add an additional 20% uncertainty. Experiments were performed at 295 ± 2 K and 700 torr total pressure of nitrogen diluent. The reactions of Cl and F atoms with CF3COOH are of no atmospheric importance. Rainout is believed to be the dominant mechanism by which CF3COOH is removed from the atmosphere. The results from this study are discussed with respect to the design and interpretation of laboratory studies of the atmospheric chemistry of CFC replacements. © 1995 John Wiley & Sons, Inc.
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  • 133
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    International Journal of Chemical Kinetics 27 (1995), S. 203-204 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pressure to publish is a common feature of university life. As a result it is now rare to find that a considerable body of excellent experimental work can lie hidden in unpublished Ph.D. theses. In North America the availability of Dissertation Abstracts has given access to the summaries of theses which might otherwise have passed notice by interested workers and this has often led to the avoidance of unnecessary duplication of work. In other countries such informative details can remain unnoticed in university libraries. From my own experience of over 48 years in research in chemical kinetics I know of a substantial group of unpublished Ph.D. theses which resulted from over 20 years of research supervision by Dr. Charles Horrex of the University of St. Andrews, Scotland. Unlike most academics he was unduly cautious in publishing work which he supervised even though this was urged upon him by the examiners of these theses, myself included. As a result, from all the work which he initiated in St. Andrews (1947-77) only one preliminary communication resulted [1], and the studies which dealt with the enthalpy of formation and reactions of benzyl radicals are known only to a very small number of gas kineticists. I therefore wish to draw the attention of the community of kineticists to the following Ph.D. theses which are deposited in the Library of the University of St. Andrews. © 1995 John Wiley & Sons, Inc.
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  • 134
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    International Journal of Chemical Kinetics 27 (1995), S. 261-275 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The gas-phase reactions of the OH radical with 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone have been investigated in the presence of NOx. Acetone and 2-methylpropanal were identified and qualified as products of both reactions. The acetone yield from 2,6-dimethyl-4-heptanone increased after addition of NO to reacted mixtures, indicating that acetone is formed through the intermediary of an acyl radical. The acetone and 2-methylopropanal formation yields were determined to be 0.78 ± 0.06 and 0.071 ± 0.011, respectively, from 4-methyl-2-pentanone and 0.68 ± 0.11 and 0.385 ± 0.034, respectively, from 2,6-dimethyl-4-heptanone. The possible reaction mechanisms are discussed and compared with these product data, and it is concluded that the experimental data provide direct evidence for isomerization of the (CH3)2CHCH2C(O)CH2C(O) (CH3)2 alkoxy radical formed from 2,6-dimethyl-4-heptanone. However, the isomerization rates of the alkoxy radicals formed from the ketones depend on whether the H-atom abstracted is on a carbon atom α or β to the 〉C=O group, with H-atom abstraction from C—H bonds on the β carbon atoms being significantly faster than from C—H bonds on the α carbon atoms. © 1995 John Wiley & Sons, Inc.
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  • 135
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    International Journal of Chemical Kinetics 27 (1995), S. 309-309 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 136
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    International Journal of Chemical Kinetics 27 (1995), S. 287-304 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The temperature dependence of the rate coefficients for the OH radical reactions with toluene, benzene, o-cresol, m-cresol, p-cresol, phenol, and benzaldehyde were measured by the competitive technique under simulated atmospheric conditions over the temperature range 258-373 K. The relative rate coefficients obtained were placed on an absolute basis using evaluated rate coefficients for the corresponding reference compounds. Based on the rate coefficient k(OH + 2,3-dimethylbutane) = 6.2 × 10-12 cm3 molecule-1s-1, independent of temperature, the rate coefficient for toluene kOH = 0.79 × 10-12 exp[(614 ± 114)/T] cm3 molecule-1 s-1 over the temperature range 284-363 K was determined. The following rate coefficients in units of cm3 molecule-1 s-1 were determined relative to the rate coefficient k(OH + 1,3-butadiene) = 1.48 × 10-11 exp(448/T) cm3 molecule-1 s-1: o-cresol; kOH = 9.8 × 10-13 exp[(1166 ± 248)/T]; 301-373 K; p-cresol; kOH = 2.21 × 10-12 exp[(943 ± 449)/T]; 301-373 K; and phenol, kOH = 3.7 × 10-13 exp[(1267 ± 233)/T]; 301-373 K. The rate coefficient for benzaldehyde kOH = 5.32 × 10-12 exp[(243 ± 85)/T], 294-343 K was determined relative to the rate coefficient k(OH + diethyl ether) = 7.3 × 10-12 exp(158/T) cm3 molecule-1 s-1. The data have been compared to the available literature data and where possible evaluated rate coefficients have been deduced or updated. Using the evaluated rate coefficient k(OH + toluene) = 1.59 × 10-12 exp[(396 ± 105)/T] cm3 molecule-1 s-1, 213-363 K, the following rate coefficient for benzene has been determined kOH = 2.58 × 10-12 exp[(-231 ± 84)/T] cm3 molecule-1 s-1 over the temperature range 274-363 K and the rate coefficent for m-cresol, kOH = 5.17 × 10-12 exp[(686 ± 231)/T] cm3 molecule-1 s-1, 299-373 K was determined relative to the evaluated rate coefficient k(OH + o-cresol) = 2.1 × 10-12 exp[(881 ± 356)/T] cm3 molecule-1 s-1. The tropospheric lifetimes of the aromatic compounds studied were calculated relative to that for 1,1,1-triclorethane = 6.3 years at 277 K. The lifetimes range from 6 h for m-cresol to 15.5 days for benzene. © 1995 John Wiley & Sons, Inc.
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  • 137
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    International Journal of Chemical Kinetics 27 (1995), S. 331-341 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Butadiene diluted with Ar was heated behind reflected shock waves over the temperature and the total density range of 1100-1600 K and 1.36 × 10-5 - 1.75 × 10-5 mol/cm3. The major products were 1,3-butadiene, 1-butyne, 2-butyne, vinylacetylene, diacetylene, allene, propyne, C2H6, C2H4, CH4, and benzene, which were analyzed by gas chromatography. The UV kinetic absorption spectroscopy at 230 nm showed that 1,2-butadiene rapidly isomerizes to 1,3-butadiene from the initial stage of the reaction above 1200 K. In order to interpret the formation of 1,3-butadiene, 1-butyne, and 2-butyne, it was necessary to include the parallel isomerizations of 1,2-butadiene to these isomers. The present data were successfuly modeled with a 82 reaction mechanism. From the modeling, rate constant expressions were derived for the isomerization 1,2-butadiene = 1,3-butadiene to be k3 = 2.5 × 1013 exp(-63 kcal/RT) s-1 and for the decomposition 1,2-butadiene = C3H3 + CH3 to be k6 = 2.0 × 1015 exp(-75 kcal/RT) s-1, where the activation energies, 63 kcal/mol and 75 kcal/mol, were assumed. These rate constants are only applicable under the present experimental conditions, 1100-1600 K and 1.23-2.30 atm. © 1995 John Wiley & Sons, Inc.
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  • 138
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    International Journal of Chemical Kinetics 27 (1995), S. 369-377 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of O(3P) with CF3NO (k2) as a function of temperature. Our results are described by the Arrhenius expression k2(T) = (4.54 ± 0.70) × 10-12 exp[(-560± 46)/T] cm3molecule-1 s-1 (243 K ≤ T ≤ 424 K); errors are 2σ and represent precision only. The O(3P) + CF3NO reaction is sufficiently rapid that CF3NO cannot be employed as a selective quencher for O2(a1Δg) in laboratory systems where O(3P) and O2(a1Δg) coexist, and where O(3P) kinetics are being investigated. © 1995 John Wiley & Sons, Inc.
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  • 139
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    International Journal of Chemical Kinetics 27 (1995) 
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    Keywords: Chemistry ; Physical Chemistry
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    Topics: Chemistry and Pharmacology
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  • 140
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    International Journal of Chemical Kinetics 27 (1995), S. 613-622 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the gas-phase reactions of the Cl atom with a series of alkanes have been determined at 296 ± 2 K using a relative rate method. Using a rate constant for the Cl atom reaction with n-butane of 1.94 × 10-10 cm3 molecule-1 s-1, the rate constants obtained (in units of 10-11 cm3 molecule-1 s-1) were: 2-methylpentane, 25.0 ± 0.8; 3-methylpentane, 24.8 ± 0.6; cyclohexane, 30.8 ± 1.2; cyclohexane-d12, 25.6 ± 0.8; 2,4-dimethylpentane, 25.6 ± 1.2; 2,2,3-trimethylbutane, 17.9 ± 0.7; methylcyclohexane, 34.7 ± 1.2; n-octane, 40.5 ± 1.2; 2,2,4-trimethylpentane, 23.1 ± 0.8; 2,2,3,3-tetramethylbutane, 15.6 ± 0.9; n-nonane, 42.9 ± 1.2; n-decane, 48.7 ± 1.8; and cis-bicyclo[4.4.0]decane, 43.1 ± 0.8, where the indicated errors are two least-squares standard deviations and do not include the uncertainties in the n-butane rate constant. These data have been combined with rate constants obtained previously for ten C2—C7 alkanes and this entire data set has been used to develop an estimation method allowing the room temperature rate constants for the reactions of the Cl atom with alkanes to be calculated. © 1995 John Wiley & Sons, Inc.
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  • 141
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    International Journal of Chemical Kinetics 27 (1995) 
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    Topics: Chemistry and Pharmacology
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  • 142
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    International Journal of Chemical Kinetics 27 (1995), S. 997-1008 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients for the reaction of O(3P) with the biogenic hydrocarbons Δ3-carene, α-pinene, and isoprene have been measured using a direct method for the first time. O(3P) was generated from the pulsed photolysis of NO2 or O3 at 308 nm, and measured by resonance fluorescence at 131 nm. Rate coefficients at room temperature for the biogenics are similar: (3.4 ± 0.6) × 10-11, (3.7 ± 0.6) × 10-11, and (3.5 ± 0.6) × 10-11 cm3 molec-1 s-1, for Δ3-carene, α-pinene, and isoprene, respectively. The rate coefficients for the reaction of O(3P) with NO2 and ethene were also measured with the same method, and these values are within 4% and 10% of the currently recommended values, respectively. The correlation between OH and O(3P)-alkene reaction rate coefficients is updated and discussed. © 1995 John Wiley & Sons, Inc.
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  • 143
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    International Journal of Chemical Kinetics 27 (1995), S. 1009-1020 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rate coefficients have been measured for the reaction of OH radicals with methylglyoxal from 260 to 333 K using the discharge flow technique and laser-induced fluorescence detection of OH. The rate coefficient was found to be (1.32±0.30) × 10-11 cm3 molecule-1 s-1 at room temperature, with a distinct negative temperature dependence (E/R of -830 ± 300 K). These are the first measurements of the temperature dependence of this reaction. The reaction of OH with acetaldehyde was also investigated, and a rate coefficient of (1.45 ± 0.25) × 10-11 cm3 molecule-1 s-1 was found at room temperature, in accord with recent studies. Experiments in which O2 was added to the flow showed regeneration of OH following the reaction of CH3CO radicals with O2. However, chamber experiments at atmospheric pressure using FTIR detection showed no evidence for OH production. FTIR experiments have also been used to investigate the chemistry of the CH3COCO radical formed by hydrogen abstraction from methylglyoxal. © 1995 John Wiley & Sons, Inc.
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  • 144
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    International Journal of Chemical Kinetics 27 (1995), S. 1055-1064 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation kinetics of malic acid by vanadium(V) in aqueous sulphuric acid was investigated at 303 K by monitoring the appearance of vanadium(IV) at 760 nm. The reaction showed first-order behavior with respect to vanadium(V), malic acid, and hydrogen ion concentration, respectively, regardless of the ionic strength. The reaction rate is enhanced by an increase in ionic strength and a decrease of the dielectric constant of the medium by addition of methanol. The activation parameters were estimated by varying the temperature in the range of 293 K to 313 K to 313 K. An oxidation mechanism is proposed, involving different vanadium(V) species produced in the presence of sulphuric acid. © 1995 John Wiley & Sons, Inc.
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  • 145
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    International Journal of Chemical Kinetics 27 (1995), S. 1097-1109 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We propose a new high temperature pathway for NO formation that involves the reaction of NNH with oxygen atoms. This reaction forms the HNNO* energized adduct via a rapid combination reaction; HNNO* then rapidly dissociates to NH + NO. The rate constant for O + NNH = NH + NO is calculated via a QRRK chemical activation analysis to be 3.3 × 1014 T-0.23exp(+510/T) cm3 mol-1 s-1. This reaction sequence can be an important or even major route to NO formation under certain combustion conditions. The presence of significant quantities of NNH results from the reaction of H with N2. The H + N2 = NNH reaction is only ca. 6 kcal/mol endothermic with a relatively low barrier. The reverse reaction, NNH dissociation, has been reported in the literature to be enhanced by tunneling. Our analysis of NNH dissociation indicates that tunneling dominates. We report a two-term rate constant for NNH dissociation: 3.0 × 108 + [M] {1.0 × 1013T0.5exp(-1540/T)} s-1. The first term accounts for pressure-independent tunneling from the ground vibrational state, while the second term accounts for collisional activation to higher vibration states from which tunneling can also occur. ([M] is the total concentration in units of mol cm-3.) Use of this dissociation rate constant and microscopic reversibility results in a large rate constant for the H + N2 reaction. As a result, we find that NNH = H + N2 can be partially equilibrated under typical combustion conditions, resulting in NNH concentrations large enough for it to be important in bimolecular reactions. Our analysis of such reactions suggests that the reaction with oxygen atoms is especially important. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 1179-1196 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The methyl-methyl reaction was studied in a shock tube using uv narrowline laser absorption to measure time-varying concentration profiles of CH3. Methyl radicals were rapidly formed initially by pyrolysis of various precursors, azomethane, ethane, or methyl iodide, dilute in argon. The contributions of the various product channels, C2H6, C2H5 + H, C2H4 + H2, and CH2 + CH4, were examined by varying reactant mixtures and temperature.The measured rate coefficients for recombination to C2H6 between 1200 and 1800 K are accurately fit using the unimolecular rate coefficients reported by Wagner and Wardlaw (1988). The rate coefficient for the C2H5 + H channel was found to be 2.4 (±0.5) × 1013 exp(-6480/T) [cm3/mol-s] between 1570 and 1780 K, and is in agreement with the value reported by Frank and Braun-Unkhoff (1988). No evidence of a contribution by the C2H4 + H2 channel was found in ethane/methane/argon mixtures, although methyl profiles in these mixtures should be particularly sensitive to this channel. An upper limit of approximately 1011 [cm3/mol-s] over the range 1700 to 2200 K was inferred for the rate coefficient of the C2H4 + H2 channel. Between 1800 and 2200 K, methyl radicals are also rapidly removed by CH3 + H ⇒ 1CH2 + H2. In this temperature range, the reverse reaction was found to have a rate coefficient of 1.3 (±0.3) × 1014 [cm3/mol-s], which is 1.8 times the room-temperature value. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 843-848 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of gas-phase thermolysis reactions of 2-acetylcyclopentanone 1,2-acetylcyclohexanone 2, N-acetylcaprolactam 3,2-acetylbutyrolactone 4,2-acetyl-2-methylbutyrolactone 5, and 3-acetyl-2-oxazolidinone 6 have been measured over a temperature range of 50 K. They undergo unimolecular first-order elimination reactions for which log A = 11.7, 11.7, 11.2, 11.4, 11.5, and 11.1 s-1 and Ea = 193.4, 189.5, 153.2, 201.0, 206.8, and 176.1 kJ mol-1, respectively. The effect of the ring size together with the effect of a heteroatom in the ring on the rate of thermolysis reactions for compound 1-6 is the subject of this work. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 867-881 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and mechanism of the thermal reduction of NO by H2 have been investigated by FTIR spectrometry in the temperature range of 900 to 1225 K at a constant pressure of 700 torr using mixtures of varying NO/H2 ratios. In about half of our experimental runs, CO was introduced to capture the OH radical formed in the system with the well-known, fast reaction, OH + CO → H + CO2. The rates of NO decay and CO2 formation were kinetically modeled to extract the rate constant for the rate-controlling step, (2) HNO + NO → N2O + OH. Combining the modeled values with those from the computer simulation of earlier kinetic data reported by Hinshelwood and co-workers (refs. [3] and [4]), Graven (ref.[5]), and Kaufman and Decker (ref. [6]) gives rise to the following expression: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_2 \, = \,\,10^{12.93\, \pm \,0.13} \,{\rm exp}\left[ { - {{\left({14,890\, \pm \,360} \right)} \mathord{\left/ {\vphantom {{\left({14,890\, \pm \,360} \right)} T}} \right. \kern-\nulldelimiterspace} T}} \right]\,{\rm cm}^{\rm 3} \,{\rm mol}^{ - 1} \,{\rm s}^{ - 1} $$\end{document}.This encompasses 45 data points and covers the temperature range of 900 to 1425 K. RRKM calculations based on the latest ab initio MO results indicate that the reaction is controlled by the addition/stabilization processes forming the HN(O)NO intermediate at low temperatures and by the addition/isomerization/decomposition processes producing N2O + OH above 900 K. The calculated value of k2 agrees satisfactorily with the experimental result. © 1995 John Wiley & Sons, Inc.
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  • 149
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    International Journal of Chemical Kinetics 27 (1995), S. 925-928 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The second-order rate constant for the oxidation of NADH by methylene blue at pH 9.0 and 25°C under aerobic conditions is 4.21 M-1 s-1. © 1995 John Wiley & Sons, Inc.
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  • 150
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    Topics: Chemistry and Pharmacology
    Notes: Rate constants for the gas-phase reactions of the four oxygenated biogenic organic compounds cis-3-hexen-1-ol, cis-3-hexenylacetate, trans-2-hexenal, and linalool with OH radicals, NO3 radicals, and O3 have been determined at 296 ± 2 K and atmospheric pressure of air using relative rate methods. The rate constants obtained were (in cm3 molecule-1 s-1 units): cis-3-hexen-1-ol: (1.08 ± 0.22) × 10-10 for reaction with the OH radical; (2.72 ± 0.83) × 10-13 for reaction with the NO3 radical; and (6.4 ± 1.7) × 10-17 for reaction with O3; cis-3-hexenylacetate: (7.84 ± 1.64) × 10-11 for reaction with the OH radical; (2.46 ± 0.75) × 10-13 for reaction with the NO3 radical; and (5.4 ± 1.4) × 10-17 for reaction with O3; trans-2-hexenal: (4.41 ± 0.94) × 10-11 for reaction with the OH radical; (1.21 ± 0.44) × 10-14 for reaction with the NO3 radical; and (2.0 ± 1.0) × 10-18 for reaction with O3; and linalool: (1.59 ± 0.40) × 10-10 for reaction with the OH radical; (1.12 ± 0.40) × 10-11 for reaction with the NO3 radical; and (4.3 ± 1.6) × 10-16 for reaction with O3. Combining these rate constants with estimated ambient tropospheric concentrations of OH radicals, NO3 radicals, and O3 results in calculated tropospheric lifetimes of these oxygenated organic compounds of a few hours. © 1995 John Wiley & Sons, Inc.
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  • 151
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    International Journal of Chemical Kinetics 27 (1995), S. 1021-1031 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the pH range 4.3-13, the reaction between N-methylacetamide (NMA) and sodium hypochlorite in dilute aqueous solution to give N-chloro-N-methylacetamide (CINMA) was found to be far slower than analogous reactions affording N-chloramines or N-chloroamino acids. The rate expression for chlorination was first-order each in [NMA] and [Cltot] (the total concentration of chlorinating species). A rate constant calculated for chlorination by each chlorinating species indicated that the order of increasing reactivity was HClO 〈 ClO- 〈 Cl2 〈 CH3COOCl (formed in the presence of acetic/acetate buffer). At pH 〉 7 the reaction rate was unaffected by variations in [Cl-] or pH, but under acidic conditions the rate increased with [Cl-] and decreasing pH. Regardless of pH, the reaction rate was not affected by changes in ionic strength. The influence of temperature on the reaction rate was also studied which allowed calculation of thermodynamic activation parameters for the N-chlorination reaction. © 1995 John Wiley & Sons, Inc.
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  • 152
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    International Journal of Chemical Kinetics 27 (1995), S. 1065-1074 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of ethyl tert-butyl ether (ETBE) from ethanol (EtOH) and tert-butyl alcohol (TBA) in the liquid phase was studied by using ion exchange resin, Amberlyst 15 (A15) in the H+ form and heteropoly acid, H0.5Cs3.5SiW12O40(HPA). Experiments were carried out in a stirred batch reactor with different temperatures under atmospheric pressure. It was found that water will inhibit the reaction rates greatly and the dehydration of TBA could not be neglected in this study.A kinetics model which considered the inhibition of water and the decrease of volume was proposed. The experimental results agreed well with the model. © 1995 John Wiley & Sons, Inc.
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  • 153
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    International Journal of Chemical Kinetics 27 (1995), S. 1111-1120 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate coefficients of the reactions of NCO radicals with NO and NO2: (1) NCO + NO → products (293-836 K) and : (2) NCO + NO2 → products (294-774 K) were measured by means of laser photolysis and laser induced fluorescence technique in the indicated temperature ranges. NCO radicals were produced from the reaction of CN, from photodissociation of ICN or BrCN, with O2. The concentration of NCO was monitored with a dye laser set at 414.95 nm. We determined k1 = 1.73 × 10-5 T-2.01 exp(-470/T) cm3 molecule-1 s-1 that agrees with published results at room temperature and confirms the temperature dependence of an early report. A non-Arrhenius negative temperature dependence of k2 was observed in this work that agrees satisfactorily with results for a shock tube18 near 1250 K. We obtained k2 = 6.4 × 10-10 T-0.646 exp(164/T) cm3 molecule-1 s-1 for 1250 K ≥ T ≥ 294 K by combining data of these two measurements. Our result at 294 K and the temperature dependence disagree with results of two previous investigations. © 1995 John Wiley & Sons, Inc.
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  • 154
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    International Journal of Chemical Kinetics 27 (1995), S. 1165-1178 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of NO (0 to 400ppm) to mixtures of H2 (ca. 1%) and O2 (0.7 to 22%) has been studied over the temperature range 700 to 825 K, in a flow reactor at atmospheric pressure. The overall effect of NO is to promote the oxidation of H2 but high concentrations of O2 actually inhibit the NO-promoted oxidation of H2.A detailed kinetic mechanism has been constructed and found to describe the experimental observations. The promotion of the oxidation of H2 arises through the catalytic cycle The ability of R.34 to reactivate chains normally terminated by the formation of HO2 is a key feature of this system.The predictions are highly sensitive to the rate of the reaction R.5 and the rate constants for this reaction is the only adjustable parameter required in the model. The value of k5,N2 found to describe all the results \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{5,{\rm N}_2 } \, = \,2.60\, \times \,10^{15} \,\exp (+ 1350\,{\rm cal}{\rm .mol}^{{\rm - 1}} /RT)cm^6 .mol^{ - 2} .s^{ - 1} $$\end{document} has an absolute uncertainty 〈35%. The uncertainty relative to other important rate constants in the H2—O2 system is less than 10%. © 1995 John Wiley & Sons, Inc.
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  • 155
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    International Journal of Chemical Kinetics 27 (1995), S. 59-71 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of S atoms with O2 was studied behind reflected shock waves applying atomic resonance absorption spectroscopy (ARAS) for concentration measurements of S and O atoms. S atoms were generated either by laser-flash photolysis (LFP) of CS2 or by the high-temperature pyrolysis of COS, respectively. The concentrations of O2 in the mixtures ranged between 50 ppm and 400 ppm, and those of the S precursors, CS2 and COS, between 5 and 25 ppm. The rate coefficient of the reaction was determined from the observed decay of the S absorption signals for temperatures 1220 K ≤ T ≤ 3460 K. The measured O-atom concentration profiles in COS/O2/Ar reaction systems were evaluated, using simplified kinetic mechanism, to verify the given rate coefficient k5. In experiments with the highest value of the [O2]/[COS] ratio the measured O-atom concentrations were found to be sensitive to the reaction: The fitting of the calculated O-atom profiles to the measured ones results in mean value of: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_6 = 8.0 \times 10^{11} \,{\rm cm}^{\rm 3} \,{\rm mol}^{{\rm - 1}} \,{\rm s}^{{\rm - 1}} $$\end{document} which is to be valid for the temperature range 2570 K ≤ T ≤ 2980 K.A first-order analysis of the observed S absorption decay in LFP shock wave experiments on CS2/Ar gas mixtures resulted in a rate coefficient of the background reaction (R4): for temperatures 1260 K ≤ T ≤ 1820 K. © 1995 John Wiley & Sons, Inc.
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  • 156
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  • 157
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    International Journal of Chemical Kinetics 27 (1995), S. 123-151 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of laboratory and modelling experiments on the oxidation of propene in the gas phase has been undertaken to determine conditions which give high yields of propene oxide. The conditions under which the experiments were conducted were 505-549 K and up to 4 bar pressure. It is proposed that propene oxide is formed from propene by reaction with several peroxy radicals including HO2 and CH3CO3. However, one of the more important radicals is hydroxypropylperoxy. Its reaction with propene, under these conditions is more important than concerted decomposition to formaldehyde and acetaldehyde. © 1995 John Wiley & Sons, Inc.
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  • 158
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    International Journal of Chemical Kinetics 27 (1995), S. 219-233 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title reaction, a key elementary process involved in the chemistry of molecular clouds, has been theoretically studied over the 5-600 K temperature range. Rate constants calculations have been carried out using the full version of the statistical adiabatic channel model in conjunction with a potential energy surface that has been derived from recent ab initio quantum chemical data. By using various switching functions, the influence of the attenuation of the bound-complex bending frequency upon N—OH bond elongation on the temperature dependence of the reaction was investigated. The rate constants exhibit a slightly positive temperature dependence with a calculated rate constant value at 300 K in very good agreement with the measured value. A comparison with the available experimental data between 250 and 515 K suggests that recrossing trajectories might occur with increasing importance as the temperature increases. However, the nonstatistical recrossing effects are expected to be of minor importance at interstellar temperatures such that the rate constants over the 5-200 K temperature range are given by k = 8.41 × 10-12 T+0.30 cm3 molecule-1 s-1. The rate constant calculated at 10 K is consistent with that derived in the astrochemical modeling of the L134N dark cloud. Rate constants for individual quantum states are also presented. © 1995 John Wiley & Sons, Inc.
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  • 159
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    Notes: The kinetics of the reactions of ground state oxygen atoms with trans-2-butene, cis-2-butene, 2-methylpropene, 2-methyl-2-butene, and 2,3-dimethyl-2-butene was investigated in the temperature range 200 to 370K. In this range, the rate constants are (in units 10-11 cm3 s-1): (1.1 ± 0.1) exp[+(180 ± 24)K/T]; (0.98 ± 0.09) exp[+(149 ± 23)K/T]; (1.14 ± 0.13) exp[+(128 ± 33)K/T]; (2.34 ± 0.16) exp[+(250 ± 16)K/T]; and (3.31 ± 0.50) exp[+(257 ± 36)K/T], respectively. The atoms were generated by the H2 laser photolysis of NO and detected by the time resolved chemiluminescence in the presence of NO. The concentrations of the O(3P) atoms were kept so low that secondary reactions with products are unimportant. © 1995 John Wiley & Sons, Inc.
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  • 160
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    Keywords: Chemistry ; Physical Chemistry
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  • 161
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    International Journal of Chemical Kinetics 27 (1995), S. 321-330 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Butyne diluted with Ar was heated behind reflected shock waves over the temperature range of 1100-1600 K and the total density range of 1.36 × 10-5-1.75 × 10-5 mol/cm3. Reaction products were analyzed by gas-chromatography. The progress of the reaction was followed by IR laser kinetic absorption spectroscopy. The products were CH4, C2H2, C2H4, C2H6, allene, propyne, C4H2, vinylacetyiene, 1,2- butadiene, 1,3-butadiene, and benzene. The present data were successfully modeled with a 80 reaction mechanism. 1-Butyne was found to isomerize to 1,2-butadiene. The initial decomposition was dominated by 1-butyne → C3H3 + CH3 under these conditions. Rate constant expressions were derived for the decomposition to be k7 = 3.0 × 1015 exp(-75800 cal/RT) s-1 and for the isomerization to be k4 = 2.5 × 1013 exp(-65000 cal/RT) s-1. The activation energy 75.8 kcal/mol was cited from literature value and the activation energy 65 kcal/mol was assumed. These rate constant expressions are applicable under the present experimental conditions, 1100-1600 K and 1.23-2.30 atm. © 1995 John Wiley & Sons, Inc.
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  • 162
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    International Journal of Chemical Kinetics 27 (1995), S. 343-350 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of atomic chlorine with neopentane was studied in the gas phase with the Very Low Pressure Reactor (VLPR) technique over the temperature range 273-333 K. The absolute reaction rate was found to be temperature-independent, and the average rate constant was k1 = (1.11± 0.13) × 10-10 cm3 molecule-1 s-1 within experimental error. The reaction proceeds via metathesis of a hydrogen atom with no activation energy, and leads to the formation of HCl and neopentyl radical. © 1995 John Wiley & Sons, Inc.
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  • 163
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    International Journal of Chemical Kinetics 27 (1995), S. 359-368 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Time-resolved resonance fluorescence detection of atomic chlorine following 266-nm laser flash photolysis of Cl2CO/RSR'/N2 mixtures has been employed to study the kinetics of Cl reactions with H2S(k1), CH3SH(k2), D2S(k3), and CD3SD(k4) as a function of temperature (193-431 K) and pressure (25-600 torr). Arrhenius expressions which describe our results are (units are 10-11 cm3molecule-1s-1; uncertainties are 2σ, precision only) k1 = (3.69 ± 0.33) exp[(208 ± 24)/T], k2 = (11.9 ± 1.7) exp[(151 ± 38)/T], and k3 = (1.93 ± 0.32) exp[(168 ± 42)/T]. The Cl + CD3SD reaction has been studied at 299 K and 396 K; values for k4 at these two temperatures are essentially the same as those measured for k2. Our results are compared with earlier studies and the mechanistic implications of observed negative activation energies and H—D kinetic isotope effects are discussed. © 1995 John Wiley & Sons, Inc.
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  • 164
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    International Journal of Chemical Kinetics 27 (1995), S. 391-402 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A pulse radiolysis system was used to study the kinetics of the reaction of FC(O)O2 radicals with NO2. By monitoring the rate of the decay of NO2 using its absorption at 400 nm the reaction rate constant was determined to be (5.5 ± 0.6) × 10-12 cm3 molecule-1 s-1 at 296 K and 500-1000 mbar pressure of SF6 diluent. A long path length Fourier transform infrared spectrometer was used to investigate the thermal stability of the product FC(O)O2NO2. The rate of thermal decomposition of FC(O)O2NO2 was independent of the total pressure of N2 diluent over the range 100-700 torr and was fit by the expression k-3 = 6.0 × 1016 exp(-14150/T) s-1. The results are discussed in the context of the atmospheric chemistry of FCOx radicals. © 1995 John Wiley & Sons, Inc.
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  • 165
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    International Journal of Chemical Kinetics 27 (1995), S. 431-441 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stoichiometry, equilibrium, and kinetics of the photo-induced disproportionation of iodomalonic acid to I-, I2, and tartronic acid have been studied by means of spectrophotometry and iodide selective electrode at 20.0 ± 0.2°C, pH 2.0-4.0. At pH 〉 2.9, only I- and HOCH(COOH)2 are detected as major products and the reaction reaches 100% conversion. At pH 〈 2.9, I2 and malonic acid are also formed and the reaction stops at a conversion rate less than 100%. Both UV (band with a peak at 360 nm) and visible light (480 nm) have been found to be effective. Two primary photochemical processes are identified: While both reactions are sensitive to UV light, only (M2) can be affected by visible light. (M1) and (M2) are considered to initiate a chain reaction sequence in which I· radicals oxidize iodomalonic acid. Dual effects of reaction products on the reaction rate have been observed: while iodine increases the efficiency of visible light and accelerates the reaction, malonic acid inhibits the photo-decomposition by mediating the recombination of I· radicals to I2. © 1995 John Wiley & Sons, Inc.
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  • 166
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    International Journal of Chemical Kinetics 27 (1995), S. 167-179 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Absolute rate constants and their temperature dependencies were determined for the addition of hydroxymethyl radicals (CH2OH) to 20 mono- or 1,1-disubstituted alkenes (CH2 = CXY) in methanol by time-resolved electron spin resonance spectroscopy. With the alkene substituents the rate constants at 298 K (k298) vary from 180 M-1s-1 (ethyl vinylether) to 2.1 middot; 106 M-1s-1 (acrolein). The frequency factors obey log A/M-1s-1 = 8.1 ± 0.1, whereas the activation energies (Ea) range from 11.6 kJ/mol (methacrylonitrile) to 35.7 kJ/mol (ethyl vinylether). As shown by good correlations with the alkene electron affinities (EA), log k298/M-1s-1 = 5.57 + 1.53 · EA/eV (R2 = 0.820) and Ea = 15.86 - 7.38 · EA/eV (R2 = 0.773), hydroxymethyl is a nucleophilic radical, and its addition rates are strongly influenced by polar effects. No apparent correlation was found between Ea or log k298 with the overall reaction enthalpy. © 1995 John Wiley & Sons, Inc.
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  • 167
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  • 168
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    International Journal of Chemical Kinetics 27 (1995), S. 379-389 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidation of benzyl alcohol and methoxy-, chloro-, and nitro- substituted benzyl alcohols by permanganate has been studied in aqueous and acetic acid medium in presence of perchloric acid. The reaction is first-order in [MnO4-] and [XC6H4CH2OH], but the order is complex with respect to [H+]. Different thermodynamic parameters have been evaluated. The reaction occurs through the protonation of alcohol in a fast preequilibrium followed by a slow rate-determining oxidation step. A two-electron transfer oxidation step has been suggested for benzyl alcohol and chloro- and nitro- substituted alcohols, while the oxidation of methoxy compounds involves a one-electron transfer via a free-radical mechanism. © 1995 John Wiley & Sons, Inc.
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  • 169
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    International Journal of Chemical Kinetics 27 (1995), S. 419-429 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics and mechanism of the removal of M2+ from bis-(heptane-2,4,6-trionato)M(II) [M = Ni, Co] by ethylenediminetetraacetic acid (EDTA), nitrilotriacetic acid (NAT), 1,2-cyclohexanediamine-N, N, N′, N′-tetraacetic acid (CyDTA), and ethylenebis(oxyethylenenitrilo)tetraacetic acid (EGTA) have been investigated using stopped-flow spectrophotometry in methanol-water at 25°C and ionic strength 0.1 mol dm-3 KNO3. The reactions were investigated at a number of different pHs.An associative mechanism is proposed to account for the kinetic data. Although all the ligands have similar functional groups, their reactivity towards the parent complex is quite different. The pH dependence of the rate constants has been used to determine the relative reactivities of the various ligand species present. In the case of nitrilotriacetic acid, a nonlinear dependence on ligand concentration is observed, thus confirming the mechanism proposed. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 473-490 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetic stopped flow method has been used to study the reaction rates of Ni(II) and Pd(II) with methioninehydroxamate (MX). Two reaction rates were observed in the MX—Ni(II) system whereas three rates were observed in the MX—Pd(II) system. Most of the rate steps were dependent on pH as well as on TMX (total concentration of methioninehydroxamate). The observed pseudo-first-order rate constants at constant pH are expressed empirically as kobsi = mi + m′i TMX. The parameters mi and m′i are pH-dependent. It has been concluded that hydroxy metal species contributed to the explanation of the rate of the metal complexation with MX. Similar systems have been correlated with the systems of current work. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 507-515 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of permanganate oxidation of L-phenylalanine in acid medium at a constant ionic strength has been investigated spectrophotometrically. An autocatalytic reaction was observed being autocatalyzed by a soluble form of Mn(IV).The reaction appears to involve a parallel consecutive reaction process in which Mn(IV) is formed as an intermediate and Mn(II) as a reaction product. A tentative mechanism consistent with the kinetics is discussed. © 1995 John Wiley & Sons, Inc.
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    International Journal of Chemical Kinetics 27 (1995), S. 547-553 
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Atomic resonance absorption spectroscopy (ARAS) was applied to measure S atoms, behind shock waves in COS/H2 pyrolysis or CS2/H2 photolysis systems. Both the pyrolysis of COS and the photolysis CS2 was used to generate the S atoms, which subsequently reacts with H2 via the reaction: The photolysis experiments were designed to provide clear first-order conditions for reaction (R3); i.e., the H2 concentration exceeds that of S by at least a factor of 100. The S atom profiles obtained during pyrolysis of highly diluted COS/H2/Ar mixtures were analyzed by computer simulations based on a simplified reaction mechanism using the rate coefficient k3 as a fitting parameter. Both groups of experiments covered the temperature range of 1257 K ≤ T ≤ 3137 K and lead to a rate coefficient of: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \,\, = \,\,6.0 \times 10^{14} \,{\rm exp}\left({ - 12070{{\rm K} \mathord{\left/ {\vphantom {{\rm K} T}} \right. \kern-\nulldelimiterspace} T}} \right){\rm cm}^{\rm 3} \,{\rm mol}^{ - 1} \,{\rm s}^{ - 1} $$\end{document}. © 1995 John Wiley & Sons, Inc.
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  • 173
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    International Journal of Chemical Kinetics 27 (1995), S. 605-612 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the acqueous-phase reactions of the free radicals ·OH, ·Cl2-, and SO4-· with the halogenated acetates, CH2FCOO-, CHF2COO-, CF3COO-, and with CH2ClCOO-, CHCl2COO-, CCl3COO- were investigated. Generally, the reactivity decreases with increasing halogen substitution and is in the order k(·OH) 〉 k(SO4-·) 〉 k(·Cl2-), but there is no general relation between the effect on reactivity of chlorine and fluorine substitution. © 1995 John Wiley & Sons, Inc.
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  • 174
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    International Journal of Chemical Kinetics 27 (1995), S. 403-418 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pulses of Br(2P3/2) and Br(2P1/2) (=Brast;) have been exposed to Teflon (PTFE) and to polycrystalline Ni surfaces in a Knudsen cell. The Br and Br* atom densities have been measured as a function of time using [3 + 2] Resonance Enhanced Multiphoton Ionization (REMPI) at 461.9 and 459.1 nm, respectively, and an absolute calibration of the sum of the density of Br and Br* on Teflon at ambient temperature has been measured to result in identical values within experimental error for both Br and Br*, namely γ(Br) = (5.6 ± 1.5) · 10-5, if an appropriate correction for the radiative lifetime of Br* of 0.77 s-1 is applied. The uptake coefficients for Br and Br* on polycrystalline Ni seem to be identical: γ(Br) = γ(Br*) = (5.6 ± 1.8) · 10-3 and independent of temperature in the range 295 to 500 K. A possible exception is the value for γ(Br*) of 2.3 · 10-3 at T = 295 K which seems to be significantly lower than the remainder of the uptake data. In the temperature range 500 to 700 K the uptake coefficients for both Br and Br* can be expressed as \documentclass{article}\pagestyle{empty}\begin{document}$$ \gamma = 0.18 \cdot \,\exp ( - 3300/RT),\,R - 1.987\,{\rm cal}\,{\rm mol}^{{\rm - 1}} \,{\rm K}^{{\rm - 1}} $$\end{document}. The system has a small positive activation energy in the range 3.3 to 4.5 kcal/mol. Br* seems to be less reactive than Cl* with respect to surface deactivation on poly Ni by a factor of six. In analogy to Cl the present system is characterized by kinetic complications in conjunction with the reversible surface poisoning of bromine, both atomic and molecular, on surfaces of Teflon (PTFE) and poly Ni that leads to the decrease of Br and Br* uptake with increasing exposure. © 1995 John Wiley & Sons, Inc.
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  • 175
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    International Journal of Chemical Kinetics 27 (1995), S. 443-451 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of oxidation of twenty six S-arylmercaptoacetic acids (SAMA) (I) by sodium perborate (PB) have been studied in acid medium. The product of oxidation is the corresponding thiophenol. The rate data of meta-and para-substituted acids have been correlated with DSP equations. While the para-compounds correlate well with σI and σR° values, the meta-compounds correlate well with σI and σR- values. The reaction constants are negative and of smaller magnitudes. Further, the ortho-substituted acids show a good correlation with a triparametric equation involving Taft's σI and R° and Charton's steric parameter ν. There is a considerable steric contribution to the total ortho-substituent effect. Based on these observations, mechanism involving the formation of protonated arylsulfinylacetic acid intermediate, followed by an intramolecular rearrangement leading to the product thiophenol has been proposed. © 1995 John Wiley & Sons, Inc.
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  • 176
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    International Journal of Chemical Kinetics 27 (1995), S. 491-498 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the bromate ion-iodide ion-L-ascorbic acid clock reaction was investigated as a function of temperature and pressure using stopped-flow techniques. Kinetic results were obtained for the uncatalyzed as well as for the Mo(VI) and V(V) catalyzed reactions. While molybdenum catalyzes the BrO3--I- reaction, vanadium catalyzes the direct oxidation of ascorbic acid by bromate ion. The corresponding rate laws and kinetic parameters are as follows. Uncatalyzed reaction: r2 = k2[BrO3-] [I-][H+]2, k2 = 38.6 ± 2.0 dm9 mol-3 s-1, ΔH
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  • 177
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    International Journal of Chemical Kinetics 27 (1995), S. 517-523 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Gas-phase elimination reactions of pentane-2,4-dione, methyl acetoacetate, ethyl acetoacetate, 3-phenylhydroazopentane-2,4-dione, and ethyl 3-oxo-2-phenyl-hydrazonobutyrate have been measured in the temperature ranges of 744-783, 662-695, 614-663, 604-664, and 503-555 K, respectively, using a flow-thermolysis technique. These compounds undergo unimolecular first-order elimination reactions, for which log A = 11.9, 11.2, 11.7, 11.5, and 11.7 s-1 and Ea = 198.3, 167.1, 141.7, 165.6, and 141.7 kJ mol-1, respectively. The kinetic data and product analysis shows that the reactions are highly affected by the electronic nature of the substituents at the carbonyl and methylene carbon atoms of the substrates investigated. © 1995 John Wiley & Sons, Inc.
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  • 178
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    International Journal of Chemical Kinetics 27 (1995), S. 561-568 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oscillatory reaction between potassium bromate and gallic acid in sulfuric acid medium has been studied calorimetrically with and without ferroin indicator. Enthalpy changes during oscillations have increased with increasing bromate concentration in presence and absence of the indicator. Prominent catalytic activity of the indicator has been observed. An initial large enthalpy change has been observed in both uncatalyzed and catalyzed conditions prior to the starting of oscillation. Attempts have been made to correlate the main thermal events with the proposed mechanism of the reaction. © 1995 John Wiley & Sons, Inc.
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  • 179
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    International Journal of Chemical Kinetics 27 (1995), S. 597-604 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dependence of the activation energy upon the extent of conversion has been discovered for the thermal decomposition of Cu4OCl6L4 with piperidine (1), morpholine (2), and triphenylphosphine oxide (3) as the ligand (L). Within the interval of conversions 0-0.3 the process shows a decrease in the activation energy (230-130 (1), 130-50 (2), and 200-100 (3) kJ mol-1). The processes considered show an isokinetic relationship with Tiso = 255 ± 15 K which corresponds to a vibrational frequency of viso = 177 ± 10 cm-1. This value accords well with IR absorption bands assigned to the stretching vibration in the trigonal CuCl3 chromophore as predicted by theory. Based on this, an assumption about the CuCl3-group as a central site of the reaction can be made. The IR- and X-ray data are presented to support the assumption made. © 1995 John Wiley & Sons, Inc.
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  • 180
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    Topics: Chemistry and Pharmacology
    Notes: Kinetics of regioselective N2 alkylation of a series of 5-(R-phenyl)tetrazoles with isopropyl alcohol has been studied in 88.2, 94.3, and 98.3% (w/w) sulfuric acid at 25°. The true rate constants were evaluated, logarithms of which were found to correlate with σ° constants of phenyl substituents as log k = -0.488 σ° - 0.417. Small value of Hammett constant ρ is evidence of a considerable isolation of the reaction center from the influence of the substituent at position C5 of the heteroring. This conclusion is confirmed by results of MNDO quantum chemical calculations of a series of 5-substituted tetrazolium cations. A correlation between logarithms of the true rate constants and the calculated net effective charges on atoms N2(N3) for 5-(R-phenyl)tetrazolium cations has been revealed. © 1995 John Wiley & Sons, Inc.
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  • 181
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    Topics: Chemistry and Pharmacology
    Notes: The formation constants of the Schiff bases of pyridoxal 5′-phosphate with polyallylamine were determined over the pH range of the acetic-acetate buffer (3.9-5.5) at an ionic strength of 0.1 M and a temperature of 25°C. The results were consistent with the rapid formation of an ionized carbinolamine, T+, followed by deprotonation, in the rate-determining step, to a neutral carbinolamine, T°. Subsequent dehydration of T° in a rapid step yields the final Schiff base. The formation of T+ is a concerted process subject to specific acid catalysis. © 1995 John Wiley & Sons, Inc.
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  • 182
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    International Journal of Chemical Kinetics 27 (1995), S. 987-995 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of the title substrates with a series of secondary alicyclic amines are subjected to a kinetic study in 44 wt% aqueous ethanol, at 25.0deg;C, ionic strength 0.2 M (maintained with KCl). Pseudo-first-order kinetics are found under amine excess. The order in amine obtained is one in the reactions of all amines. The Brönsted-type plots for the overall second-order rate coefficients are biphasic with slopes β1 = 0.3 (high pKa), β2 = 0.95 (low pKa) for the aminolysis of the 4-nitro derivative, and β1 = 0.3 and β2 = 0.80 for the aminolysis of the dinitro compound; the pKa values at the curvature center are pKa0 = 9.8 and 9.5, respectively. From a comparison of these pKa0 values with those found in the same reactions in water and the shapes of the Brönsted-type plots, it is concluded that these reactions are stepwise, with the formation of a zwitterionic tetrahedral intermediate in the reaction pathway. © 1995 John Wiley & Sons, Inc.
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  • 183
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    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of base hydrolysis of (αβS) (salicylato) (tetraethylenepentamine) cobalt(III) have been investigated in aquo-organic solvent media at 15.0 〈 t, °C 〈 40.0, and I = 0.10 mol dm (ClO4-) using propane-2-ol (≤70% v/v), t-butanol (≤60% v/v), acetone (≤70% v/v), acetonitrile (≤50% v/v), and ethylene glycol (≤70% v/v) as cosolvents. Both the spontaneous and base-catalyzed hydrolysis of the phenoxide species [(tetren)CoO2CC6H4O]+ were appreciably accelerated by the cosolvents PriOH, ButOH, Me2CO, and MeCN. On the contrary the base hydroylsis (k2) was retarded while spontaneous aquation (k1) was accelerated to a small extent with increased EG content. Variation of log k1 and log k20 (k20 = k2 at I = 0) with mole fraction (X0.S) or reciprocal of the relative permitivity (Ds-1) of the media were nonlinear. The transfer free energy of the transition state relative to that of the initial state of the substrate for transfer of species from water to mixed solvents also varied nonlinearly with X0.S, or Ds-1 indicating solvent specificity. The activation parameters, ΔH≠ and ΔS≠ varied nonlinearly with solvent composition exhibiting extrema. The preferential solvation and solvent structural effects mediated the kinetics and energetics of the reaction. © 1995 John Wiley & Sons, Inc.
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  • 184
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    International Journal of Chemical Kinetics 27 (1995), S. 1075-1087 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simultaneous, quantitative, narrow-line laser absorption measurements of CN time-histories at 388.444 nm and OH time-histories at 306.687 nm have been made in incident and reflected shock wave experiments using dilute mixtures of nitiric acid (HNO3) and HCN in argon. The thermal decomposition of HNO3 serves as a rapid source of OH upon shock-heating, and the OH subsequently reacts predominantly with the HCN in the test gas mixture. The rate coefficient for the reaction was determined in the temperature range 1120-1960 K via detailed kinetics modeling of the simultaneously acquired CN and OH measurements. These data are in good agreement with lower temperature measurements of the rate of the reverse reaction (-1a) when recent values of the heats of formation of CN and HCN are used. The expression \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1a} \, = \,3.90\, \times \,10^6 T^{1.83} \exp (- 5179/T)cm^3 mol^{ - 1} s^{ - 1}, $$\end{document} valid for temperatures 500 to 2000 K, effectively represents the experimental measurements. The estimated uncertainty of the expression for k1a is ±30%, based on the experimental uncertainties of the individual rate coefficient studies. Analysis of the decay region of the experimental OH time-histories yielded the total rate coefficient k1 (all product channels) for the reaction of HCN with OH for temperatures ranging from 1490 to 1950 K. These measurements are consistent with a previous theoretical analysis of the three primary addition-isomerization-dissociation processes for the HCN + OH reaction at combustion temperatures when the contribution to k1 from reaction (1a) is included. © 1995 John Wiley & Sons, Inc.
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  • 185
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    International Journal of Chemical Kinetics 27 (1995) 
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    Keywords: Chemistry ; Physical Chemistry
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    Topics: Chemistry and Pharmacology
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  • 186
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    International Journal of Chemical Kinetics 27 (1995), S. 1151-1164 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermal decomposition of CF2HCl has been modeled using 2,269 thermally activated reactions and 63 chemically activated processes. Thermochemical properties for the species involved are calculated using statistical mechanics and group contribution theory, and reaction rate constants are determined using transition state theory. The theoretical predictions, obtained without fitting any parameter values, afree closely with available experimental data. Also, the reactions that control the distribution of reaction products are identified, and this, in turn, permits simplification of the reaction set. Sensitivity studies show that uncertainties in the calculations do not alter the predicted trends in behavior or the main reaction pathways. © 1995 John Wiley & Sons, Inc.
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  • 187
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    International Journal of Chemical Kinetics 27 (1995), S. 1207-1220 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The NH3/NO2 system has been investigated experimentally in an isothermal flow reactor in the temperature range 850-1350 K. The experimental data were interpreted in terms of a detailed reaction mechanism. The flow reactor results, supported by a theoretical analysis of the NH2—NO2 complex, suggest that the NH2 + NO2 reaction has two major product channels, both proceeding without activation barriers: Our findings indicate that the N2O + H2O channel is dominant at low temperatures while H2NO + NO dominates at high temperatures. The rate constant for reaction (R21) is estimated to be 3.5 · 1012 cm3/mol-s in the temperature range studied with an uncertainty of a factor of 3. © 1995 John Wiley & Sons, Inc.
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  • 188
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    Keywords: Chemistry ; Physical Chemistry
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  • 189
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rates of gas-phase elimination reactions of N-benzoyl and N-acetyl-propanamide and N-benzoyl and N-acetyl-2-methylpropanamide are measured and discussed. They undergo unimolecular first-order elimination reactions. The reactivities of N-benzoylamides have been compared with each other and with those of N-acetylamides. The kinetic data together with the product analysis reveals that, the statistical factor of the availability of β-hydrogen atoms for elimination as well as steric factor are obscured by polar factor in gas-phase elimination reactions of N-benzoylamides while the statistical factor rather than electronic effect operates in each of N-acetylamides. © 1995 John Wiley & Sons, Inc.
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  • 190
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    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the solvolysis of the hydrophobic ion, Co(4-t-Bupy)4Cl2+, have been followed in mixtures of water with co-solvents having a hydrophilic tendency, ethane-1,2-diol and 2-methoxyethanol. The variation of In(rate constant) with the reciprocal of the dielectric constant is nonlinear for both co-solvents. The enthalpy and the entropy of activation are rather insensitive to changes in the solvent composition in both mixtures, but low maxima may exist at mol fractions of co-solvent Ca. 0.10-0.20. The application of a Gibbs energy cycle to the process of the initial state going to the transition state suggest that, in water-rich conditions, the increase in the stability of the emergent solvated CoIII ion in the transition state relative to the increase in the stability of Co(4-t-Bupy)4Cl2+ in the initial state as the co-solvent content rises is greater for 2-methoxyethanol than for ethane-1,2-diol. © 1995 John Wiley & Sons, Inc.
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  • 191
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    International Journal of Chemical Kinetics 27 (1995), S. 7-16 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of oxidation of ethanol by cerium(IV) in presence of ruthenium(III) (in the order of 10-7 mol dm-3) in aqueous sulfuric acid media have been followed at different temperatures (25-40°C). The rate of disappearance of cerium(IV) in the title reaction increases sharply with increasing [C2H5OH] to a value independent of [C2H5OH] over a large range (0.2-1.0 mol dm-3) in which the rate law conforms to: \documentclass{article}\pagestyle{empty}\begin{document}$$ -2.303\frac{{d\log [{\rm Ce}^{{\rm IV}}]}}{{dt}} = k_{obsd} = (k_c + k_d [{\rm H}^{\rm + }]^{ - 1})[{\rm Ru}]_T $$\end{document} where [Ru]T gives the total ruthenium (III) concentration. The values of 10-3kc and 10-3kd are 3.6 ± 0.1 dm3 mol-1 s-1 and 3.9 ± 0.2 s-1, respectively, at 40°C, I = 3.0 mol dm-3. The proposed mechanism involves the formation of ruthenium(III)- substrate complex which undergoes oxidation at the rate determining step by cerium(IV) to form ruthenium(IV)- substrate complex followed by the rapid red-ox decomposition giving rise to the catalyst and ethoxide radical which is oxidized by cerium(IV) rapidly. The mechanism is consistent with the existence of the complexes RuIII · (C2H5OH) and RuIII · (C2H5O-) and both are kinetically active. The overall bisulphate dependence conforms to: kobsd = A[Ru]T/{1 + C[HSO4-]} where A = 2.2 × 104 dm3 mol-1 s-1, C = 1.3 at 40°C, [H+] = 0.5 mol dm-3, and I = 3.0 mol dm-3. The observations are consistent with the Ce(SO4)2 as the kinetically active species. © 1995 John Wiley & Sons, Inc.
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  • 192
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    International Journal of Chemical Kinetics 27 (1995), S. 37-48 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The consecutive reactions of (CH3)2Si(OC2H5)2 and CH3Si(OC2H5)3 with methoxide ions were investigated in methanol solutions. The reverse transesterification reactions with ethoxide ions could be neglected in both cases since the concentration of ethoxide in methanol solution was assumed to be low due to the fast equilibrium reaction C2H5O- + CH3OH ⇌ C2H5OH + CH3O-. The progress of the reactions was followed by monitoring the formation of ethanol with a Fourier-transform infrared spectrometer. All rate constants were determined at 295 K. The reactions between the dialkoxydimethylsilanes and methoxide ions were assumed to consist of two consecutive steps that can be represented by the net reaction; (CH3)2Si(OC2H5)2 + 2CH3O- → (CH3)2Si(OCH3)2 + 2C2H5O-. The two consecutive rate constants were established as 1.93 ± 0.12M-1s-1 and 1.00 ± 0.12M-1s-1, respectively. The consecutive rate constants for the reactions between the trialkoxymethylsilanes and methoxide ions can be written according to the total reaction; CH3Si(OC2H5)3 + 3CH3O- → CH3Si(OCH3)3 + 3C2H5O-. The three rate constants corresponding to each consecutive step were established as 1.12 ± 0.09 M-1s-1, 0.82 ± 0.10 M-1s-1, and 0.51 ± 0.06 M-1s-1, respectively. © 1995 John Wiley & Sons, Inc.
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  • 193
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    International Journal of Chemical Kinetics 27 (1995), S. 85-88 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of 2-bromo-3-methylbutyric acid in the gas phase was studied over the temperature range of 309.3-357.0°C and pressure range of 15.5-100.0 torr. This process, in seasoned static reaction vessels and in the presence of the free radical inhibitor cyclohexene, is homogeneous, unimolecular, and follows first-order rate law. The observed rate coefficients are represented by the following Arrhenius equations: log k1(s-1) = (12.72 ± 0.25) - (181.8 ± 2.9) kJ mol-1 (2.303RT)-1. The primary products are isobutyraldehyde, CO, and HBr. The polar five-membered cyclic transition state type of mechanism appears to be preferred in the dehydrohalogenation process of α-haloacids in the gas phase. © 1995 John Wiley & Sons, Inc.
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  • 194
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    International Journal of Chemical Kinetics 27 (1995), S. 99-108 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title amines were pyrolyzed in a stirred-flow reactor at 380-510°C, pressures of 8-15 torr and residence times of 0.3-2.4 s, using toluene as carrier gas. The substrates with an allyl group yielded propene and iminonitriles as reaction products. HCN is formed by decomposition of the iminonitriles. The first-order rate coefficients for propene formation fit the Arrhenius equations Allyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.29 \pm 0.35} {\rm exp(} - {\rm 189} \pm 5{\rm kJ/mol }RT{\rm)} $$ \end{document}Diallyl cyanomethyl amine:\documentclass{article} \pagestyle{empty} \begin{document} $$ k({\rm s}^{ - {\rm 1}}) = 10^{13.00 \pm 0.20} {\rm exp(} - {\rm 183} \pm 3{\rm kJ/mol }RT{\rm)} $$ \end{document} Diethyl cyanomethyl amine gave a 20:1 gas mixture of ehylene and ethane, plus HCN. The liquid product fraction contained mainly N-ethyl methanaldimine. The first-order rate coefficients for ethylene formation followed the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{15.30 \pm 0.24} {\rm exp(} - {\rm 226} \pm 3{\rm kJ/mol }RT{\rm)} $$\end{document} Diethyl propargyl amine decomposed cleanly into allene and N-ethyl ethanaldimine. The first-order rate coefficients for allene formation fit the Arrhenius equation \documentclass{article}\pagestyle{empty}\begin{document}$$ k({\rm s}^{ - {\rm 1}}) = 10^{12.84 \pm 0.30} {\rm exp(} - {\rm 168} \pm 4{\rm kJ/mol }RT{\rm)} $$\end{document} The results suggest that the above allyl and propargyl amines decompose unimolecularly by mechanisms involving six-center cyclic transition states. For diethyl cyanomethyl amine, a nonchain free radical mechanism is proposed. © 1995 John Wiley & Sons, Inc.
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  • 195
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    International Journal of Chemical Kinetics 27 (1995), S. 499-505 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the H2O2 decomposition in presence of Fe(III)- and Cr(III)-complexes of mono-, di-, and triethanolamine supported on Dowex-50W resin have been investigated. The decomposition process proceeded with first-order kinetics for the substrate concentration. The rate of reaction increased with increasing number of the coordinated ligands in the metal complex as well as with increasing ligand basicity. The decomposition reaction involved the formation of an intermediate active species, which converts into a peroxo-metal complex of brown, green, or gray color. A mechanism describing the decomposition process is proposed. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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  • 196
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 27 (1995) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 197
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    International Journal of Chemical Kinetics 27 (1995), S. 535-545 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The rate constants for the reaction of electron pulse produced solvated electrons and a number of solutes in water-isopropanol mixtures have been measured. The quenching of the singlet excited state of naphthalene has also been studied in the same mixtures, using triethylamine and acrylamide as quenchers. The variation of the bimolecular solvated electron reaction rate constants with the composition of the solvent has been compared with the variation in the quenching constants with the composition of the solvent. Both these variations are surprisingly similar, with acrylamide behaving in a reverse manner (to the other solutes) in both the cases. It has been possible to quantitatively correlate both sets of data using dielectric constant (∊) as a measure of polarity and the viscosity (η) as an index of the microstructure. The curves obtained provide insights with respect to the nature of charge transfer processes involved. © 1995 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 198
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    International Journal of Chemical Kinetics 27 (1995), S. 569-575 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetic study on the dissolution of CO2 from the surface of a liquid CO2 droplet in water was conducted, and a mechanism of the decay of CO2 hydrate was proposed. The model was applied to the experimental data which showed that the radius of liquid CO2 droplets in water reduced linearly with time. It was proved that the dissolution rate of CO2 into water is dominated by the decay of CO2 hydrate on the surface of the droplet. The rate constant of the decay of CO2 hydrate was estimated to be 1.25 × 10-6 m s-1. From a viewpoint of liquid CO2 disposal in the deep ocean, it is predicted that the thin membrane of CO2 hydrate at the interface between seawater and liquid CO2 will control the dissolution of CO2 into seawater. © 1995 John Wiley & Sons, Inc.
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  • 199
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    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 27 (1995) 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 200
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    International Journal of Chemical Kinetics 27 (1995), S. 627-635 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cetyltrimethylammonium permanganate (CTAP) has been prepared and characterized from IR and NMR data. At room temperature the compound is stable when kept in dark but at 115°C it undergoes a violent thermal decomposition. In different organic solvents self-oxidation takes place giving rise to pentadecanal. The rate of self-oxidation in different solvents are in the order: benzonitrile 〉 benzene 〉 chloroform 〉 carbon tetrachloride. A mechanism involving proton transfer from the β-methylene group to the permanganate ion, thereby forming an olefinic intermediate, has been suggested. The oxidation kinetics of benzyl alcohol have been studied in chloroform medium. The thermodynamic parameters for the oxidation reactions have been evaluated. © 1995 John Wiley & Sons, Inc.
    Additional Material: 3 Ill.
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