Thermal decomposition of CH3I using I-atom absorption

Kumaran, S. S.; Su, M.‐C.; Michael, J. V.

doi:10.1002/(sici)1097-4601(1997)29:7<535::aid-kin8>3.0.co;2-v

Cited by 21 publications

(46 citation statements)

References 26 publications

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“…Evidently, the reason is that the high concentration limit was not attained in [32], whereas our calculations by formulas (9)3(12) yield the rate constants k i in the high concentration limit, provided that the k 3i data were obtained in the same limit. As to the more recent data by Kumaran et al [33] (for the 10003 1700 K range), they agree with our results almost within the accuracy. To derive the kinetic parameters of reactions (5)3(8), we have to obtain the equilibrium constants K c,j ( j = 538).…”

Section: äääääääääääáäääääääáäääääääääääääáääääääääääääáääääääääääääásupporting

confidence: 94%

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

2004

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The wave functions and enthalpies of formation of the ground states of iodomethanes CH 4 3x I x and iodomethyl radicals CH 3 3x I x . (x = 133) were calculated ab initio with regard to electron correlation. The geometries of the molecules of these compounds were determined, as well as the normal mode frequencies and other parameters, which were used for calculating the thermodynamic functions in the 031500 K range.These functions were used for calculating the constants of the CH 4 3x I x 76 47 CH 4 3x I x 31 + I and CH 4 3x I x + I 76 47 CH 4 3x I x 31 + I 2 equilibria, which, in turn, were used for calculating the corresponding rate constants in the high concentration limit.Studies of gas-phase pyrolysis of alkyl halides have been successfully used in developing fundamentals of chemical kinetics for almost a century [1,2]. The key reactions for the alkyl halides being pyrolyzed are those between (halo)alkyl radical and atomic hydrogen: R . + H . 76 RH, halogen: R . + Hlg . 76 RHlg, or hydrogen halide molecules: R . + HHlg 76 RH + Hlg . , Hlg = Cl, Br, I.Hence, these pyrolytic experiments furnish kinetic and thermochemical information about free radicals [336]. For the last-named reactions (CH 3 . + HI, CH 3 . + HBr, C 2 H 5 . + HBr, CH 2 Br . + HI...), peculiar phenomenon of a negative activation energy was recently discovered [739], whose nature still remains to be elucidated [10313]. Accurate thermodynamic and kinetic parameters of chloro-, bromo-, and iodoalkanes and their corresponding radicals are also essential for solving less fundamental but practically vital problems, such as, e.g., simulation of the Earth ozone layer depletion or modeling of incineration of halogencontaining waste.

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confidence: 94%

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

2004

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“…Note that at long times [I] becomes constant indicating that CH3I has completely dissociated. The ratio, [T]d[CH3I]o, is the yield, and in this case, we found a yield of (1.04 k 0.09) for 1238ST.11820 K [23]. This shows unambiguously that CH3 + I is the only important pathway and that singlet methylene and HI (molecular elimination)…”

Section: Resultssupporting

confidence: 62%

“…[ls], CH3Cl [10,11], C3H3Cl [19], CFC13 [16,20], CF2C12 [16,21], CF3Cl [16,22], CF2HCl [13], CF3I [12], CH3I [23], C2H5I [24], C6H5I [25], and CC120 [26]. The methods used are nearly identical in all cases, and for the purposes of discussion, we will illustrate the method with CH3I data -ln(IdIo) (It and Io refer to transmitted and incident I-atom resonance light intensities, respectively), is measured as CH3I decomposes.…”

Section: Resultsmentioning

confidence: 99%

Thermal Decomposition Studies of Halogenated Organic Compounds

Michael¹,

Kumaran²

1998

Combustion Science and Technology

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“…At the intermediate temperatures near 1600 K in Table 1, only eleven processes contribute with the predominant process in the initial stages of reaction being eq 1b, as shown by the sensitivity analysis of Figure 2. At short times, there is slight sensitivity to CH 3 I dissociation 21 and, at longer times, also from HO 2 dissociation.…”

Section: Resultsmentioning

confidence: 97%

“…For the profile at 1303 K in Figure 1 and the other lower T experiments in Table 1, sensitivity analysis shows that only two reactions are important in determining [OH] t , CH 3 I dissociation and reaction 1b. Direct rate constant determinations on CH 3 I have already been carried out in this laboratory, 21 and changing this rate constant by its uncertainty of (35% gives only ∼(20% changes in the k 1b value that fits the experiment. Hence, experiments at the lower temperatures in the table do give direct measurements of k 1b .…”

Section: Resultsmentioning

confidence: 99%

Reflected Shock Tube Studies of High-Temperature Rate Constants for CH₃ + O₂, H₂CO + O₂, and OH + O₂

et al. 2005

J. Phys. Chem. A

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The reflected shock tube technique with multipass absorption spectrometric detection of OH-radicals at 308 nm, corresponding to a total path length of approximately 2.8 m, has been used to study the reaction CH3 + O2 CH2O + OH. Experiments were performed between 1303 and 2272 K, using ppm quantities of CH3I (methyl source) and 5-10% O2, diluted with Kr as the bath gas at test pressures less than 1 atm. We have also reanalyzed our earlier ARAS measurements for the atomic channel (CH3 + O2 --> CH3O + O) and have compared both these results with other earlier studies to derive a rate expression of the Arrhenius form. The derived expressions, in units of cm3 molecule(-1) s(-1), are k = 3.11 x 10(-13) exp(-4953 K/T) over the T-range 1237-2430 K, for the OH-channel, and k = 1.253 x 10(-11) exp(-14241 K/T) over the T-range 1250-2430 K, for the O-atom channel. Since CH2O is a major product in both reactions, reliable rates for the reaction CH2O + O2 --> HCO + HO2 could be derived from [OH]t and [O]t experiments over the T-range 1587-2109 K. The combined linear least-squares fit result, k = 1.34 x 10(-8) exp(-26883 K/T) cm3 molecule(-1) s(-1), and a recent VTST calculation clearly overlap within the uncertainties in both studies. Finally, a high sensitivity for the reaction OH + O2 --> HO2 + O was noted at high temperature in the O-atom data set simulations. The values for this obtained by fitting the O-atom data sets at later times (approximately 1.2 ms) again follow the Arrhenius form, k = 2.56 x 10(-10) exp(-24145 K/T) cm3 molecule(-1) s(-1), over the T-range, 1950-2100 K.

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Thermal decomposition of CH3I using I-atom absorption

Cited by 21 publications

References 26 publications

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

Thermal Decomposition Studies of Halogenated Organic Compounds

Reflected Shock Tube Studies of High-Temperature Rate Constants for CH₃ + O₂, H₂CO + O₂, and OH + O₂

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Thermal decomposition of CH3I using I-atom absorption

Cited by 21 publications

References 26 publications

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

Molecular, thermodynamic, and kinetic parameters of iodomethanes and iodomethyl radicals: ab initio calculations

Thermal Decomposition Studies of Halogenated Organic Compounds

Reflected Shock Tube Studies of High-Temperature Rate Constants for CH3 + O2, H2CO + O2, and OH + O2

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Reflected Shock Tube Studies of High-Temperature Rate Constants for CH₃ + O₂, H₂CO + O₂, and OH + O₂