Hydrogen Atom Attack on 1,2-Dichlorotetrafluoroethane:  Rates of Halogen Abstraction

Manion, Jeffrey A.; Tsang, Wing

doi:10.1021/jp9530109

Cited by 11 publications

(9 citation statements)

References 21 publications

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“…In the present work, the minor channel-producing propene from HME (R1543) impacts results under some of our conditions. Tsang 52 reported approximate branching values, but we additionally use later unpublished work from our laboratory 52,70,87 that confirmed his results while better characterizing the temperature dependence (see Supporting Information). The rate constant for reaction of H with HME (R1544) was taken as that recommended for generic primary hydrogens in our recent review and evaluation.…”

Section: And Propene (R1543)supporting

confidence: 68%

Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE)

Mertens

Manion

2020

Int J of Chemical Kinetics

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We have used the single-pulse shock tube technique with postshock GC/MS product analysis to investigate the mechanism and kinetics of the unimolecular decomposition of isopropanol, a potential biofuel, and of its reaction with H atoms at 918-1212 K and 183-484 kPa. Experiments employed dilute mixtures in argon of isopropanol, a radical scavenger, and, for H-atom studies, two different thermal precursors of H. Without an added H source, isopropanol decomposes in our studies predominantly by molecular dehydration. Added H atoms significantly augment decomposition, mainly by abstraction of the tertiary and primary hydrogens, reactions that, respectively, lead to acetone and propene as stable organic products. Traces of acetaldehyde were observed in some experiments above ≈ 1100 K and establish branching limits for minor decomposition pathways. To quantitatively account for secondary chemistry and optimize rate constants of interest, we employed the method of uncertainty minimization using polynomial chaos expansions (MUM-PCE) to carry out a unified analysis of all datasets using a chemical model-based originally on JetSurF 2.0. We find: k(isopropanol → propene + H 2 O) = 10 (13.87 ± 0.69) exp(−(33 099 ± 979) K/ T) s −1 at 979-1212 K and 286-484 kPa, with a factor of two uncertainty (2σ), including systematic errors. For H atom reactions, optimization yields: k(H + isopropanol → H 2 + p-C 3 H 6 OH) = 10 (6.25 ± 0.42) T 2.54 exp(−(3993 ± 1028) K /T) cm 3 mol −1 s −1 and k(H + isopropanol → H 2 + t-C 3 H 6 OH) = 10 (5.83 ± 0.37) T 2.40 exp(−(1507 ± 957) K /T) cm 3 mol −1 s −1 at 918-1142 K and 183-323 kPa. We compare our measured rate constants with estimates used in current combustion models and discuss how hydrocarbon functionalization with an OH group affects H abstraction rates.

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Section: And Propene (R1543)supporting

confidence: 68%

Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE)

Mertens

Manion

2020

Int J of Chemical Kinetics

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“…Mesitylene reacts with hydrogen atoms to form either H 2 + 3,5-dimethylbenzyl radicals or m-xylene + methyl radicals. This latter reaction is the only source of m-xylene in this system, providing a means to determine H-atom concentrations, using the known 12 Methyl radicals can also abstract hydrogen from mesitylene to form CH 4 + 3,5-dimethylbenzyl radicals. The resonantly stabilized dimethylbenzyl radicals do not undergo significant further reaction during the heating pulse, effectively preventing H and CH 3 radicals from reacting with the reactant or reference species.…”

Section: Methodsmentioning

confidence: 99%

“…Mesitylene reacts with hydrogen atoms to form either H 2 + 3,5-dimethylbenzyl radicals or m -xylene + methyl radicals. This latter reaction is the only source of m -xylene in this system, providing a means to determine H-atom concentrations, using the known ratio of methyl displacement to H abstraction, k d / k a = exp(−1086/ T ). Methyl radicals can also abstract hydrogen from mesitylene to form CH 4 + 3,5-dimethylbenzyl radicals.…”

Section: Methodsmentioning

confidence: 99%

Ring-Expansion Reactions in the Thermal Decomposition of tert-Butyl-1,3-cyclopentadiene

2006

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The thermal decomposition of tert-butyl-1,3-cyclopentadiene has been investigated in single-pulse shock-tube studies at shock pressures of 182-260 kPa and temperatures of 996-1127 K. Isobutene (2-methylpropene), 1,3-cyclopentadiene, and toluene were observed as the major stable products in the thermolysis of dilute mixtures of the substrate in the presence of a free-radical scavenger. Hydrogen atoms were also inferred to be a primary product of the decomposition and could be quantitatively determined on the basis of products derived from the free-radical scavenger. Of particular interest is the formation of toluene, which involves the expansion of the ring from a five- to a six-membered system. The overall reaction mechanism is suggested to include isomerization of the starting material; a molecular elimination channel; and C-C bond fission reactions, with toluene formation occurring via radical intermediates formed in the latter pathway. These radical intermediates are analogous to those believed to be important in soot formation reactions occurring during combustion. Molecular and thermodynamic properties of key species were determined from G3MP2B3 quantum chemistry calculations and are reported. The temperature dependence of the product spectrum was fit with a detailed chemical kinetic model, and best-fit kinetic parameters were derived using a Nelder-Mead simplex minimization algorithm. Our mechanism and rate constants are consistent with and provide experimental support for the H-atom-assisted routes to the conversion of fulvene to benzene that have been proposed in the literature on the basis of theoretical investigations.

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“…Rate constants for the reaction of OH radicals with hexamethylbenzene (HMB), k (OHϩHMB) , as well as for the H-atom reaction with both aromatics, k (HϩTMB) and k (HϩHMB) , are not available at least for the desired temperature region. As a result of a shock-tube study (T ϭ 970 -1140 K), a relative value for k (HϩTMB) is reported not applicable to room-temperature conditions [7]. Therefore, the subject of this work is to determine the rate constants k (OHϩHMB) , k (HϩTMB) , and k (HϩHMB) at room temperature.…”

Section: Introductionmentioning

confidence: 99%

Rate constants for the gas-phase reaction of hexamethylbenzene with OH radicals and H atoms and of 1,3,5-trimethylbenzene with H atoms

Berndt

Böge

2001

Int. J. Chem. Kinet.

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Rate constants for the gas‐phase reaction of hexamethylbenzene (HMB) with OH radicals and H atoms and of 1,3,5‐trimethylbenzene (TMB) with H atoms have been obtained in a flow system at 295 ± 2 K and a pressure of 25 mbar He using MS measurements. Obtained rate constants from a relative rate technique are k(OH+HMB) = (1.13 ± 0.11) 10−10, k(H+HMB) = (5.9 ± 3.4) 10−13 and k(H+TMB) = (4.6 ± 2.7) 10−13 cm3 molecule−1 s−1, respectively. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 124–129, 2001

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Hydrogen Atom Attack on 1,2-Dichlorotetrafluoroethane: Rates of Halogen Abstraction

Cited by 11 publications

References 21 publications

Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE)

Kinetics of isopropanol decomposition and reaction with H atoms from shock tube experiments and rate constant optimization using the method of uncertainty minimization using polynomial chaos expansions (MUM‐PCE)

Ring-Expansion Reactions in the Thermal Decomposition of tert-Butyl-1,3-cyclopentadiene

Rate constants for the gas-phase reaction of hexamethylbenzene with OH radicals and H atoms and of 1,3,5-trimethylbenzene with H atoms

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