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Notes: Rate constants for the reaction of 1-chloro-2,3-epoxypropane with p-cresol in the presence of basic catalysts were studied at the temperature range of 71-100°C.It was found that in the presence of sodium p-cresolate, three consecutive reactions proceeded giving the following products: 1-chloro-3-(tolyloxy)-2-propanol (CTP), 1-(p-tolyloxy)-2,3-epoxypropane (TEP) as a main product, and 1,3-di(p-tolyloxy)-2-propanol (DTP). Their rate constants at 71°C were: k1 = 0.030 ± 0.009, k2 = 1.58 ± 0.02, and k3 = 0.033 ± 0.005 dm3/mol · min, respectively.In the presence of quaternary ammonium salts, this process consisted of 5 reactions which led to CTP as a main product as well as TEP and 1,3-dichloro-2-propanol (DCP). The rate constant of CTP formation at 71°C was established, k1 = 0.130 ± 0.030 dm3/mol · min, as were the ratios of the other rate constants k2/k-4 = 1.5 ± 0.2, k5/k-4 = 20.0 ± 5.0, and k4/k1 = 0.6 ± 0.7. Based on the changes in Cl- ion concentration during the reaction, the catalystic activity of quaternary ammonium salts was explained.The kinetic model of these reactions in the presence of basic catalysts has been proposed and appropriate kinetic equations have been presented. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 73-79, 1997.

Notes: The reactions of pyrrolidine with O-ethyl S-(X-phenyl) dithiocarbonates (X = 4-methyl, 4-methoxy, H, 4-chloro, 4-nitro, 2,4-dinitro, and 2,4,6-trinitro) are subjected to a kinetic study in 44 wt% aqueous ethanol, 25.0°C, and ionic strength 0.2 M (maintained with KCl). Pseudo-first-order kinetics are found under amine excess. Linear plots of the pseudo-first-order rate coefficient against concentration of free-base pyrrolidine are obtained for all the reactions, the nucleophilic rate coefficient (kN) being the slope of such plots. The Bronsted-type plot (log kN vs. pKa for the leaving group) is linear with slope βlg = - 0.2, which is consistent with a mechanism through a tetrahedral intermediate (T±) where its formation is rate determining. The βlg value is very similar to that found in the same reactions in water. There is a great difference in the mechanism of the reactions of O-ethyl S-phenyl dithiocarbonate with pyrrolidine (order one in amine) and piperidine (complex order in amine) in aqueous ethanol, and this is attributed to a greater nucleofugality from T± of piperidine rather than pyrrolidine. © 1997 John Wiley & Sons, Inc.

Notes: The laser photolysis-long path transient absorption technique was used to study the mechanism and products of the reaction O(3P) + OClO (→M) Products (3) at 260 K in 100 to 400 torr of He, N2, and Ar. ClO was not detected as a reaction product, 〈5% yield, from this reaction at 400 torr and 260 K. A broad UV absorption feature associated with a product of this reaction, with a peak located at 260 nm, was observed. The peak absorption cross section of this species was measured to be (1.72 ± 0.12) × 10-17 cm2 molecule-1. The rate coefficient for the appearance of this species was measured to be (1.69 ± 0.46) × 10-13 cm3 molecule-1 s-1 and was independent of pressure. The rate coefficient for the appearance of the species is ca. 10 times lower than that for the disappearance of O(3P), indicating that the observed species is not a direct product of the reaction of O(3P) with OClO. Mechanistic considerations and the possible identity of the absorber are discussed. © 1997 John Wiley & Sons, Inc.

Notes: The deactivation of I(2P½) by R-OH compounds (R = H, CnH2n+1) was studied using time-resolved atomic absorption at 206.2 nm. The second-order quenching rate constants determined for H2O, CH3OH, C2H5OH, n-C3H7OH, i-C3H7OH, n-C4H9OH, i-C4H9OH, s-C4H9OH, t-C4H9OH, are respectively, 2.4 ± 0.3 × 10-12, 5.5 ± 0.8 × 10-12, 8 ± 1 × 10-12, 10 ± 1 × 10-12, 10 ± 1 × 10-12, 11.1 ± 0.9 × 10-12, 9.8 ± 0.9 × 10-12, 7.1 ± 0.7 × 10-12, and 4.1 ± 0.4× 10-12 cm3 molec-1 s-1 at room temperature. It is believed that a quasi-resonant electronic to vibrational energy transfer mechanism accounts for most of the features of the quenching process. The influence of the alkyl group and its role in the total quenching rate is also discussed. © 1997 John Wiley & Sons, Inc.

Notes: The oxidation of substituted benzyl alcohols by bis(2,2′-bipyridyl) copper(II) permanganate (BBCP), leading to the corresponding benzaldehydes is first-order with respect to BBCP. Michaelis-Menten type kinetics were observed with respect to the alcohols. The oxidation of a,a-dideuteriobenzyl alcohol indicated the presence of a substantial kinetic isotope effect. The rates of oxidation of meta- and para-substituted benzyl alcohols were correlated in terms of Charton's triparametric LDR equation whereas ortho- substituted benzyl alcohols were correlated with a four parametric LDRS equation. The results of correlation analyses point to an electron-deficient reaction center in the transition state. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 9-16, 1997.

Notes: By conducting an excimer laser photolysis (193 and 248 nm) behind shock waves, three elementary reactions important in the oxidation of H2S have been examined, where, H, O, and S atoms have been monitored by the atomic resonance absorption spectrometry. For HS + O2 → products (1), the rate constants evaluated by numerical simulations are summarized as: k1 = 3.1 × 10-11exp|-75 kJ mol-1/RT| cm3molecule-1s-1 (T = 1400-1850 K) with an uncertainty factor of about 2. Direct measurements of the rate constants for S + O2 → SO + O (2), and SO + O2 → SO2 + O (3) yield k2 = (2.5 ± 0.6) × 10-11 exp|-(15.3 ± 2.5) kJ mol-1/RT| cm3molecule-1s-1 (T = 980-1610 K) and, k3 = (1.7 ± 0.9) × 10-12 exp|-(34 ± 11) kJ mol-1/RT| cm3molecule-1s-1 (T = 1130-1640 K), respectively. By summarizing these data together with the recent experimental results on the H(SINGLE BOND)S(SINGLE BOND)O reaction systems, a new kinetic model for the H2S oxidation process is constructed. It is found that this simple reaction scheme is consistent with the experimental result on the induction time of SO2 formation obtained by Bradley and Dobson. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 57-66, 1997.

Notes: Rate constants have been measured for the reaction of OH radicals with four amides, R1N(CH3) - C(O)R2 (R1 = H or Methyl, R2 = Methyl or Ethyl), at 300 and 384 K using flash photolysis/resonance fluorescence. Reactants are introduced under slow flow conditions and are controlled by two independent methods, gas saturation and continuous injection. It turns out that the reactivities of the amides are considerably lower than those of the corresponding amines. The pattern of rate constants obtained at 300 K: 14, 21, 5.2, and 7.6 · 10-12 cm3/s for N,N-Dimethylacetamide (dmaa), N,N-Dimethylpropionamide (dmpa), N-Methylacetamide (maa), and N-Methylpropionamide (mpa), respectively, indicates a single, dominating reaction center and strong electronic effects of the substituents at both sides of the amide function. Correspondingly, the observed negative temperature dependence (E/R = - 400 to - 600 K) excludes a direct abstraction mechanism. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the reactions between sodium nitrite and phenol or m-, o-, or p-cresol in potassium hydrogen phthalate buffers of pH 2.5-5.7 were determined by integration of the monitored absorbance of the C-nitroso reaction products. At pH 〉 3, the dominant reaction was C-nitrosation through a mechanism that appears to consist of a diffusion-controlled attack on the nitrosatable substrate by NO+/NO2H2+ ions followed by a slow proton transfer step; the latter step is supported by the observation of basic catalysis by the buffer which does not form alternative nitrosating agents as nitrosyl compounds. The catalytic coefficients of both anionic forms of the buffer have been determined. The observed order of substrate reactivities (o-cresol ≈ m-cresol 〉 phenol ≫ p-cresol) is explained by the hyperconjugative effect of the methyl group in o- and m-cresol, and by its blocking the para position in p-cresol. Analysis of a plot of ΔH# against ΔS# shows that the reaction with p-cresol differs from those with o- and m-cresol as regards the formation and decomposition of the transition state. The genotoxicity of nitrosatable phenols is compared with their reactivity with NO+/NO2H2+. © 1997 John Wiley & Sons, Inc.

Notes: For a number of hydrofluorocarbons (HFCs), EHez has been found to have a linear correlation with each of the following: (i) log (k/n); (ii) A/n; and (iii) Ea/R, where EH = HOMO energy of the molecule, z = average fractional positive charge on the abstractable hydrogen atom in the molecule, k = rate constant of the gas-phase H abstraction reaction of the molecule with OH radical at 298 K, n = number of abstractable H atoms in the molecule, A = preexponential factor, and Ea/R = activation temperature of the said reaction. These correlations have been used to estimate the temperature dependent rate constants for the reactions of OH radical with CF3CF2CH2CH2CF2CF3, CF3CH2CF2CH2CF3, CF3CF2CH2CH2F, CF3CH2CH3, CF3CH2CHF2, CF3CHFCH2F, and CHF2CHFCHF2 as {6.97 × 10-13 exp(1481/T)}, {5.43 × 10-13 exp(1754/T)}, {7.95 × 10-13 exp(l308/T)}, {8.0 × 10-13 exp(1300/T)}, {7.03 × 10-13 exp(1470/T)}, {7.33 × 10-13 exp(1417/T)}, and {8.09 × 10-13 exp(1285/T)}, respectively. These have not yet been measured experimentally. Linear correlation between EHez and log (k/n) has also been observed for nine halogen substituted acetaldehydes. On the other hand, EH is found to have a better linear correlation with log (k/n) than EHez in the case of fluorinated ethers and alcohols where the available experimental data are at present limited. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 187-194, 1997.

Notes: The reaction between the radical cation derived from 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and phenols follows a kinetic law given by \documentclass{article}\pagestyle{empty}\begin{document}$$ d[ABTS^{\buildrel{+}\over{\cdot}}]/dt=k [ABTS^{\buildrel{+}\over{\cdot}}]^2[PhOH]/[ABTS] $$\end{document} with stoichiometric coefficients between one and two. The rate constant is almost unrelated to the structure of the phenol, while the number of ABTS radicals scavenged by each phenol molecule increases with para-substitution. These results are explained in terms of a fast, reversible electron transfer \documentclass{article}\pagestyle{empty}\begin{document}$$ ABTS^{\buildrel{+}\over{\cdot}}\,+PhOH {\buildrel{\longrightarrow}\over{\longleftarrow}} ABTS + PhO\bullet+H^{+} $$\end{document} followed by the self-combination of the phenoxy radicals and/or their reaction with another ABTS derived radical action. The relative rate of these processes determine the value of the stoichiometric coefficient. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 219-224, 1997.

Notes: A continuous flow-through reactor with a thin layer of solid particles (size ranging from 100 to 300 μm) was used to obtain a deeper knowledge on the mechanism of dissolution of UO2 under oxidizing conditions. Using this methodology the dissolution rate of uranium dioxide was determined at three different oxygen partial pressures (5, 21, and 100% in nitrogen) and as a function of pH (between 3 and 12) in a noncomplexing medium.From the results of these experiments the following rate equation was derived: \documentclass{article}\pagestyle{empty}\begin{document}$$ (3 〈 pH 〈 6.7)\,r\,(mol\cdot s^{-1}\cdot m^{-2})\,=\,(3.5 \pm 0.8) \cdot 10^{-8} \cdot [H^{+}]^{0.37\pm 0.01}\cdot[O_2]^{0.31\pm 0.02} $$\end{document} In addition, XPS characterizations were performed to determine the U(IV)/U(VI) ratio on the solid surface at different experimental times and conditions. These results showed that at acidic conditions (pH below 6.7) the final solid surface presents a stoichiometry close to UO2, while at alkaline conditions the final solid surface average composition is close to UO2.25. This information was integrated with the results of the leaching experiments to present a model for the mechanism of dissolution of uranium dioxide under the experimental conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 261-267, 1997.

Notes: The kinetics of the gas-phase reactions of OH radicals, NO3 radicals, and O3 with indan, indene, fluorene, and 9,10-dihydroanthracene have been studied at 297 ± 2 K and atmospheric pressure of air. The rate constants, or upper limits thereof, for the O3 reactions were (in cm3 molecule-1 s-1 units): indan, 〈 3 × 10-19; indene, (1.7 ± 0.5) × 10-16, fluorene, 〈 2 × 10-19; and 9,10-dihydroanthracene, (9.0 ± 2.0) × 10-19. Using a relative rate method, the rate constants for the OH radical and NO3 radical reactions, respectively, were (in cm3 molecule-1 s-1 units): indan, (1.9 ± 0.5) × 10-11 and (6.6 ± 2.0) × 10-15; indene, (7.8 ± 2.0) × 10-11 and (4.1 ± 1.5) × 10-12; fluorene, (1.6 ± 0.5) × 10-11 and (3.5 ± 1.2) × 10-14; and 9,10-dihydroanthracene, (2.3 ± 0.6) × 10-11 and (1.2 ± 0.4) × 10-12. These kinetic data were used to assess the relative contributions of the various reaction pathways. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 299-309, 1997.

Notes: A laser-flash photolysis/UV absorption technique has been used to study the temperature dependence (from T = 300 - 470 K) of the self-reaction kinetics of representative primary secondary and tertiary β-hydroxyperoxy radicals \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{lclr} 2\,\rm{HOCH}_2\rm{CH}_2\rm{O}_2 & \longrightarrow & 2\,\rm{HOCH}_2\rm{CH}_2\rm{O}\,+\,\rm{O}_2 & (1\rm{a})\\ & \longrightarrow & \rm{HOCH}_2\rm{CH}_2\rm{OH}\,+\rm{HOCH}_2\rm{CH}_2\rm{O}\,+\,\rm{O}_2 & (1\rm{b})\\ 2\,\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}_2 & \longrightarrow & 2\,\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}\,+\,\rm{O}_2 & (2\rm{a})\\ & \longrightarrow & \rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{OH} & \\ & &+\rm{HOCH}(\rm{CH}_3)\rm{CH}(\rm{CH}_3)\rm{O}+\rm{O}_2 & (2\rm{b})\\ 2\,\rm{HOC}(\rm{CH}_3)_2\rm{C}(\rm{CH}_3)_2\rm{O}_2 & \longrightarrow & 2\,\rm{HOC}(\rm{CH}_3)_2 \rm{C}(\rm{CH}_3)_2\rm{O}\,+\,\rm{O}_2 & (3)\\ \end{array} $$\end{document} The following Arrhenius expressions were derived for the rate coefficients of reactions (1)-(3) (in cm3 molecule -1s-1) and for the product branching ratios of reactions (1) and (2) as a function of temperature (all errors 1σ) \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l}k_1=(6.9_{+2.1}^{-1.5})\times 10 ^{-14}\,\exp[(1040\pm 100)/\rm{T}]\\ \beta_1=(3100_{+3700}^{-1700})\,\exp[(-2400\pm 280)/\rm{T}] (\hbox{ where } \beta_1=k_{1a}/k{1\rm{b}})\\ k_2=(7.7_{+12.8}^{-4.8})\times 10 ^{-15}\,\exp[(1330\pm 350)/\rm{T}]\\ \beta_2=(4.0_{+0.2}^{-0.1})\times 10 ^{4}\,\exp[(-3600\pm 100)/\rm{T}]\\ k_3=(4.7_{+6.5}^{-2.7})\times 10 ^{-13}\,\exp[(-1420\pm 320)/\rm{T}]\\ \end{array} $$\end{document} The calculated rate coefficients for reactions (1)-(3) at 298 K are therefore (in 10-13 cm3molecule -1s -1 23 ± 2, 6.7 ± 1.3, and 0.040 ± 0.012, respectively which compare well with the values measured elsewhere at this temperature using a similar technique. The product branching ratios and the Arrhenius parameters are compared with those for other substituted and unsubstituted peroxy radical self reactions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 323-331, 1997

Notes: The gas-phase reactivities of W(a5DJ, a7S3) with N2O, SO2, and NO in the temperature range of 295-573 K are reported. Tungsten atoms produced by the photodissociation of W(CO)6. The tungsten atoms were detected by a laser-induced fluorescence technique. The removal rate constants for the 6s25d4 a5Dl states were found to be pressure dependent for all of the reactants. Removal rate constants for the 6s15d5 a7S3 state were found to be fast compared to the a5DJ states and often approached the gas kinetic rate constant. The reaction rates for all the states were found to be pressure independent with respect to the total pressure. Results are discussed in terms of the different electronic configurations of the states of tungsten © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 367-375 1997

Notes: Real-time kinetic measurements are reported for the Cl + CH3CO → CH2CO + HCl reaction. The experiments utilize infrared spectroscopy to determine the time dependence of the ketene formed via this reaction and of the CO produced from the subsequent rapid reaction between chlorine atoms and ketene. The reaction is investigated over a pressure range of 10-200 torr and a temperature range of 215-353 K. Within experimental error the rate constant under these conditions is k5a = (1.8 ± 0.5) × 10-10 cm3 s-1. We have also examined the Cl + CH2CO reaction and found it to have a rate constant of k6 = (2.5 ± 0.5) × 10-10 cm3 s-1 independent of temperature. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 421-429, 1997.

Notes: The kinetics of oxidation of indigo carmine (IC) by N-sodio-N-bromotoluenesulfonamide or bromamine-T (BAT) in pH 5 buffer medium has been investigated at 30°C using spectrophotometry at 610 nm. The reaction rate shows dependencies of first-order on [IC]0 second-order on [BAT]0, fractional order on [H+], and inverse first-order on [ρ-toluenesulfonamide]. The addition of chloride and bromide ions, and the variation of ionic strength of the medium have no influence on the reaction rate. There is a negative effect of the dielectric constant of the solvent. Activation parameters have been calculated. A single-pathway mechanism for the reaction, consistent with the kinetic data, has been proposed. © John Wiley & Sons, Inc. Int J Chem Kinet 29: 453-459, 1997

Notes: The reaction of HCo(CO)4 (HT) or DCo(CO)4 (DT) with excess cinnamaldehyde (CA) in methylcyclohexane (RH) at 22.2° and under 1 atm of CO follows pseudo-first-order kinetics in HT or DT with an inverse isotopic effect of 0.54. Identified products of the reaction are hydrocinnamaldehyde (HCA) and styrene (STY). The STY is believed to be an artifact of the thermal decomposition of the true product PhCH2CH2C( (DOUBLE BOND) O)Co(CO)4 (X) or its isomer. Reduction of the carbon-carbon double bond in CA is effected by hydrogen from both the cobalt compound and RH. It is proposed that the reaction involves a free-radical chain mechanism in which the rate of the slow step is proportional to [CA]0n, the initial molar concentration of CA raised to a power of 1.5- 1.8. Additionally the rate of conversion of CA to HCA and X meets the criteria of a homocompetitive reaction with [CA], [HCA], and [STY] simple functions of t0.5 (where t is reaction time) for use of DT or (in a single case) a function of (t0.5 + t) for use of HT. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 473-481, 1997.

Notes: The reaction rates of 2-chloro-3,5-dinitropyridine 1 with a series of arylthiolates 2a-h in methanol have been measured at 25°C. The products are the corresponding 2-thioaryl-3,5-dinitropyridine 3a-h. Good Hammett correlation with ρ value-1.19 was obtained suggesting an elimination-addition mechanism SNAr and the formation of Meisenheimer-like intermediates. Plot of log k2 vs. pKa values of arylthiols gave straight line with β=0.38 indicating that the π-bond breaking in the pyridine ring is so much advanced over bond making between the nucleophile and the carbon that bears the chlorine atom. Excellent correlation between log k2 and log K(carbon basicity of arylthiolates) was obtained. © 1997 John Wiley & Sons. Inc. Int J Chem Kinet 29: 515-521, 1997.

Notes: The cracking reaction pathways and mechanisms of ethylcyclohexane and 1-cyclohexyloctane with a rare earth Y (REY) catalyst were studied. Experiments at 500°C indicated that the dominant reactions were ring opening with subsequent secondary cracking, cracking in the alkyl side chain, isomerization, and hydrogen transfer. A kinetic model of the catalytic cracking of 1-cyclohexyloctane was developed using a novel mechanism-based lumping scheme that exploits the chemical similarities within reaction families. The formal application of 17 reaction family matrices, which correspond to 13 reaction family classes, to the matrix representations of the reactants and derived products generated the model. The reaction family concept was further exploited to constrain the kinetics within each reaction family to follow a quantitative structure/reactivity Polanyi relationship. Ultimately, nine Polanyi relationship parameters and three coking/deactivation parameters were determined by optimizing the model fit to the experimental data. The resulting model correlations were excellent, as the overall parity between experimental and model values was yModel=-0.000470+0.986yExp with a correlation coefficient of 0.971. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 545-560, 1997.

Notes: The photolysis of strong alkaline (pH〉12.7) solutions of H2O2 yields O·-, which in the presence of molecular oxygen forms the ozonide radical ion, O3·-. A detailed kinetic study on the reaction mechanisms involved during formation and decay of O3·- radical ions in these solutions, in the presence and absence of added O·-/HO· scavengers is reported.In order to obtain a complete interpretation of the experimental data, kinetic computer simulations were done using a complete set of reactions. A very good agreement between experimental and computer simulated data is obtained. The following simplified mechanism accounts for the observed first-order decay of O3·- in alkaline hydrogen peroxide solutions:O·- + O2 → O3·-O3·- → O·- + O2O·- + S →OH· + S →HO· + HO2- → O2·- + H2OO·- + HO2- → O2·- + HO-With S: O·-/HO· scavengers. © 1997 John Wiley & Sons, Inc.

Notes: The kinetics of the reactions of 2-chloro-3-nitropyridine (ortho-like) and 5-nitro (para-like) isomer with morpholine and piperidine were studied in methanol and benzene at several amine concentrations and temperatures in the range 25-45°C. The data show that k3-NO2/k5-NO2 ratios are less than unity in methanol. The steric hindrance in the transition state of the 3-nitro (ortho-like) isomer retards o-substitution while the stability of p-quinonoid structure of the 5-nitro (para-like) isomer favors p-substitution. In benzene, the k3-NO2/k5-NO2 ratios are greater than unity. The hydrogen bonding formation between the ammonium hydrogen and the ortho-nitro group in the transition state of 3-nitro isomer favors the o-substitution. © 1997 John Wiley & Sons, Inc.

Notes: The rate constant for the reaction of the hydroxyl radical with 1,1,1,3,3-pentafluorobutane (HFC-365mfc) has been determined over the temperature range 278-323K using a relative rate technique. The results provide a value of k(OH+CF3CH2CF2CH3)=2.0×10-12exp(-1750±400/T) cm3 molecule-1 s-1 based on k(OH+CH3CCl3)=1.8×10-12 exp (-1550±150/T) cm3 molecule-1 s-1 for the rate constant of the reference reaction. Assuming the major atmospheric removal process is via reaction with OH in the troposphere, the rate constant data from this work gives an estimate of 10.8 years for the tropospheric lifetime of HFC-365mfc. The overall atmospheric lifetime obtained by taking into account a minor contribution from degradation in the stratosphere, is estimated to be 10.2 years. The rate constant for the reaction of Cl atoms with 1,1,1,3,3-pentafluorobutane was also determined at 298±2 K using the relative rate method, k(Cl+CF3CH2CF2CH3)=(1.1±0.3)×10-15 cm3 molecule-1 s-1. The chlorine initiated photooxidation of CF3CH2CF2CH3 was investigated from 273-330 K and as a function of O2 pressure at 1 atmosphere total pressure using Fourier transform infrared spectroscopy. Under all conditions the major carbon-containing products were CF2O and CO2, with smaller amounts of CF3O3CF3. In order to ascertain the relative importance of hydrogen abstraction from the (SINGLE BOND)CH2(SINGLE BOND) and (SINGLE BOND)CH3 groups in CF3CH2CF2CH3, rate constants for the reaction of OH radicals and Cl atoms with the structurally similar compounds CF3CH2CCl2F and CF3CH2CF3 were also determined at 298 K k(OH+CF3CH2CCl2F)=(8±3)×10-16 cm3 molecule-1 s-1; k(OH+CF3CH2CF3)=(3.5±1.5)×10-16 cm3 molecule-1 s-1; k(Cl+CF3CH2CCl2F)=(3.5±1.5)×10-17 cm3 molecule-1 s-1; k(Cl+CF3CH2CF3)〈1×10-17 cm3 molecule-1 s-1. The results indicate that the most probable site for H-atom abstraction from CF3CH2CF2CH3 is the methyl group and that the formation of carbonyl compounds containing more than a single carbon atom will be negligible under atmospheric conditions, carbonyl difluoride and carbon dioxide being the main degradation products. Finally, accurate infrared absorption cross-sections have been measured for CF3CH2CF2CH3, and jointly used with the calculated overall atmospheric lifetime of 10.2 years, in the NCAR chemical-radiative model, to determine the radiative forcing of climate by this CFC alternative. The steady-state Halocarbon Global Warming Potential, relative to CFC-11, is 0.17. The Global Warming Potentials relative to CO2 are found to be 2210, 790, and 250, for integration time-horizons of 20, 100, and 500 years, respectively. © 1997 John Wiley & Sons, Inc.

Notes: Relative rate coefficients for the reaction of acetyl (CH3CO) radicals with O2 (k4) and Cl2 (k7) have been obtained at 298 K and 228 K as a function of total pressure, using FTIR/environmental chamber techniques. Measured values of k4/k7 were placed on an absolute basis using k7=2.8×10-11 exp(-47/T) cm3 molec-1 s-1. At 298 K, the value of k4 is constant ((7±2)×10-13 cm3 molec-1 s-1) at pressures from 0.1 to 2 torr, then increases to a high pressure limiting value of (3.2±0.6)×10-12 cm3 molec-1 s-1, which is approached at pressures above 300 torr. At 228 K, the low-pressure value of k4 increases by about 20-30%, while the high pressure value remains unchanged. Experiments designed to elucidate the products of reaction (4) as a function of pressure at 298 K indicate that the reaction occurs via a concerted mechanism in which CH3CO radicals combine with O2 to give an excited acetylperoxy radical (CH3COO2*) which is increasingly stabilized at high pressure at the expense of a low pressure decomposition channel. The yield of acetylperoxy radicals from reaction (4) decreases from 〉95% at pressures above 100 torr, to about 90% at 60 torr, and 50% at 6 torr. Indirect evidence for formation of OH radicals from the low pressure decomposition is presented, although the carbon-containing coproduct(s) of this channel could not be identified. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 655-663, 1997.

Notes: The sodium-hydrogen ion exchange constant for the system sodium 1-dodecanesulfonate-hydrochloric acid in aqueous acetonitrile has been determined from the pseudo-phase ion exchange model for surfactant catalytic effects. The results indicate that the micellar system behaves similarly for the aqueous and the aqueous acetonitrile (2.106 M) solvent systems.The influence of substrate molecular structure on micellar catalysis by perfluorooctanoic acid of the hydrolysis of hydroxamic acids (R - CO - NHOH) in aqueous acetonitrile has been explored. Data for substrate structures of fifteen compounds with R=alkyl, aralkyl, alicyclylalkyl, phenylalkyl, alkyl-substituted phenylalkyl, and with chain branching at the α, β, and γ positions are compared. Relative binding constant values indicate that substrates with aromatic groups are less well solubilized in the perfluoro micellar environment than are substrates with saturated groups.There is now evidence for specific micellar effects on the reaction rate as well as general micellar catalysis. © 1997 John Wiley & Sons, Inc.

Notes: It is shown experimentally that pentafluoroethane undergoes rapid protium-deuterium exchange with water in the presence of hydroxide ion. Addition of dimethylsulfoxide enhances the rate at least by a factor of 100. The first measured fractionation factor data are presented for the temperature range of 50-120°C. These values are compared with the theoretical estimations calculated by using isotopic reduced partition function ratios based on molecular vibrational frequencies. Although catalytic exchange is slow at ambient temperature, the reaction rate becomes measureable above around 60°C because of large activation energy (92 kJ/mole). Comparisons are made with similar data available for various halomethane and haloethane systems. © 1997 John Wiley & Sons, Inc.

Notes: Experimental kineticists are always faced with the problem of reducing kinetic data to extract physically meaningful information. A particularly vexing problem arises when different models reproduce the data but yield different values for the physical parameters. For over forty-five years Monte Carlo simulation techniques have been used to study the statistical behavior of parameters extracted from data. Not only do these simulations provide realistic uncertainties, correlation coefficients, and confidence envelopes, but they also provide insight into the nature of the model. These insights may be obtained by viewing two-dimensional scatter plots of the fractional changes of the parameters and one-dimensional histograms of the distributions of the changes in the parameters. Monte Carlo simulations are illustrated with examples from OH+CH4 → CH3+H2O and the high-pressure rate coefficient for methyl-methyl association. A more complex problem involves models for pressure-dependent rate coefficients in the falloff region. We have modeled methyl-methyl association with five of the most current analytic approximations for behavior in the falloff region. All of these reproduce the data to within their uncertainties. However, when Monte Carlo techniques are applied the correlations between the parameters and the nonlinear nature of their behavior become evident. We postulate that the statistical behavior of the parameters of a model may be used to distinguish one model from another and, thereby, identify those analytic approximations that hold promise for further investigation and utilization. Finally, the recent advent of high-speed workstations implies that Monte Carlo simulations should become a routine part of the analysis of kinetic data. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 803-817, 1997

Notes: The kinetics of oxidation of benzhydrol and its p-substituted derivatives (YBH, where Y=H, Cl, Br, NO2, CH3, and OCH3) by sodium N-chloro-p-toluenesulfonamide or chloramine-T (CAT), catalyzed by ruthenium(III) chloride, in the presence of hydrochloric acid in 30% (v/v) MeOH medium has been studied at 35°C. The reaction rate shows a first-order dependence on [CAT]O and a fractional-order each on [ YBH]O, [Ru(III)], and [H+]. The reaction also has a negative fractional-order (-0.35) behavior in the reduction product of CAT, p-toluenesulfonamide (PTS). The increase in MeOH content of the solvent medium retards the rate. The variation of ionic strength of the medium has negligible effect on the rate. Rate studies in D2O medium show that the solvent isotope effect, k′H2O/k′D2O, is equal to 0.60. Proton inventory studies have been made in H2O(SINGLEBOND)D2O mixtures. The rates correlate satisfactorily with Hammett σ relationship. The LFE relationship plot is biphasic and the reaction constant ρ=-2.3 for electron donating groups and ρ=-0.32 for electron withdrawing groups at 35°C. Activation parameters ΔH≠, ΔS≠, and ΔG≠ have been calculated. The parameters, ΔH≠ and ΔS≠, are linearly related with an isokinetic temperature β=334 K indicating enthalpy as a controlling factor. A mechanism consistent with the observed kinetics has been proposed. © 1997 John Wiley & Sons, Inc.

Notes: Rate constants for three dimethylbenzaldehydes and two trimethylphenols have been determined for the OH reactions at 298±2 K and atmospheric pressure using a relative rate method. The OH reaction rate constants were placed on an absolute basis using the literature rate constant for 1,2,4-trimethylbenzene of (3.25±0.5)×10-11 cm3 molecule-1s-1). The measured rate constants were (in units of cm3 molecule-1 s-1) 2,4-dimethyl-benzaldehyde, (4.32±0.67)×10-11; 2,5-dimethylbenzaldehyde, (4.37±0.68)×10-11; 3,4-dimethylbenzaldehyde, (2.14±0.34)×10-11; and 2,3,5- trimethylphenol, (12.5±1.9)×10-11, 2,3,6-trimethylphenol, (11.8±1.8)×10-11. Using an average OH concentration of 8.7×105 molecule cm-3, the estimated atmospheric lifetimes are ca. 7.5 h for 2,4- and 2,5-dimethylbenzaldehydes, ca. 15 h for 3,4-dimethylbenzaldehyde, ca. 2.5 h for 2,3,5- and 2,3,6-trimethylphenols. The reactivities of the trimethylphenols exceed those of the dimethyl-benzaldehydes by more than a factor of 3. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 523-525, 1997.

Notes: The gas-phase reaction of NO3 radicals with isoprene was investigated under flow conditions at 298 K in the pressure range 6.8〈P(mbar)〈100 using GC-MS/FID, direct MS, and long-path FT-IR spectroscopy as detection techniques. By means of a relative rate method, the rate constant for the primary attack of NO3 radicals toward isoprene was determined to be (6.86±2.60)×10-13 cm3 molecule-1 s-1.The formation of the possible oxiranes, 2-methyl-2-vinyl-oxirane and 2-(1-methyl-vinyl)-oxirane, was observed in dependence on total pressure.In the presence of O2 in the carrier gas, the product distribution was found to be strongly dependent on the reaction pathways of formed peroxy radicals. If the peroxy radicals mainly reacted in a self-reaction, the formation of organic nitrates was detected and 4-nitroxy-3-methyl-but-2-enal was identified as a main product. On the other hand, when NO was added to the gas mixture and the peroxy radicals were converted via RO2+NO→RO+NO2, the formation of methyl vinyl ketone as the main product as well as 3-methylfuran and meth-acrolein was observed.From the ratio of the product yields if NO was added to the gas mixture it was concluded that the attack of NO3 radicals predominantly takes place in the 1-position.A reaction mechanism is proposed and the application of these results to the troposphere are discussed. © 1997 John Wiley & Sons, Inc.

Notes: Rate constants are reported for substitution at vanadium(IV) in bis-cyclopentadienylvanadium dichloride by a range of anionic and uncharged nucleophiles in acetonitrile solution. Rate constants have been determined for replacement of the first and of the second chloride. The reactivity of V(cp)2Cl2 is compared with that of Ti(cp)2Cl2. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 835-838, 1997

Notes: Fluorimetric titrations of 4-hydroxydiphenyl ether and its anion give stretched sigmoid curves with two inflection points. This reveals that the rates of excited state proton exchange are comparable to the rates of deactivation of the conjugate pair. These curves are analyzed using the lifetimes of the species. The excited state equilibrium constants determined from rate constants and by other methods are compared. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 861-867, 1997

Notes: Relative rate constant measurements have been carried out on the Cl-atom reactions with benzene, chlorobenzene, toluene, xylene, and styrene in 740 torr of air at room temperature (295 K), using the photochemical reactor-FTIR spectroscopy technique. The Cl atoms were generated by the UV photolysis of Cl2, and the reference compounds were CHF, Cl for benzene and chlorobenzene and isobutane for toluene xylene and styrene. Using the absolute rate constant for these two reference compounds reported in the literature, the following kinetic data were obtained for the study compounds (in units of cm3s-1). \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{ll} {\rm Benzene} & (1.3\pm 0.3)\times 10 ^{-15}\\ {\rm Chlorobenzen} & (9.8\pm 2.4)\times 10 ^{-16}\\ {\rm Toluene} & (5.9\pm 0.5)\times 10 ^{-11}\\ o-{\rm Xylene} & (1.5\pm 0.1)\times 10 ^{-10}\\ m-{\rm Xylene} & (1.4\pm 0.1)\times 10 ^{-10}\\ p-{\rm Xylene} & (1.5\pm 0.1)\times 10 ^{-10}\\ {\rm Styrene} & (3.6\pm 0.3)\times 10 ^{-10}\end{array} $$\end{document} The quoted error bars are for ± 2σ. The present kinetic results are compared with available literature data to update and expand the kinetics database for Cl-atom reactions of organic compounds. The results are also analyzed to provide insights into the reaction mechanism for the Cl-atom initiated oxidation of benzene under atmospheric conditions. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 349-358, 1997

Notes: The initiation reaction of the thermal decomposition of silicon tetrachloride \documentclass{article}\pagestyle{empty}\begin{document}$$ SiCl_4\,+\,M\,{\buildrel{k_1}\over{\longrightarrow}} SiCl_3\,+Cl\,+M \eqno(R1) $$\end{document} was studied behind reflected shock waves at temperatures between 1550 K and 2370 K and pressures between 1 and 1.5 bar. Atomic resonance absorption spectrometry (ARAS) was applied for time-resolved measurements of H atoms at the Lα-line in SiCl4/H2/Ar systems. Additional experiments were performed in the SiCl4/Ar system following the absorption of SiCl4 at the Lα-line. Rate coefficients for the reaction (RI) were determined to be: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1=4.8\times 10^{16}\exp(-40954 K/T) cm^3 mol^{-1} s^{-1}. $$\end{document} The choice between two possible alternatives of the first decomposition step, namely elimination of either Cl2 or Cl, has been made in favor of the second reaction on the basis of kinetic and energetic considerations. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 415-420, 1997.