Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study

Huybrechts, G.; Eerdekens, K.

doi:10.1002/1097-4601(200103)33:3<191::aid-kin1013>3.0.co;2-8

Cited by 2 publications

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References 18 publications

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“…The DFT-calculated threshold energies for 1,2-HF elimination from CH 3 CF 2 Cl and CH 3 CFCl 2 are in accord with the experimental results, but the calculated E 0 (HCl) are always too small. The E 0 (HCl) for these two molecules are in modest agreement from thermal , and chemical-activation experiments, , and the experimental values seem to be established. The inability of the computational methods to match the experimental E 0 (1,2-HCl) from the CH 3 CHFCl, CH 3 CFCl 2 , and CH 3 CF 2 Cl series is a consequence of the overweighting of the carbocation contribution to the transition states, but the explanation of why this occurs remains to be discovered.…”

Section: Discussionmentioning

confidence: 73%

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

et al. 2015

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Vibrationally excited CD3CHFCl molecules with 96 kcal mol(-1) of energy were generated by the recombination of CD3 and CHFCl radicals in a room-temperature bath gas. The four competing unimolecular decomposition reactions, namely, 1,1-HCl and 1,2-DCl elimination and 1,1-HF and 1,2-DF elimination, were observed, and the individual rate constants were measured. The product branching fractions are 0.60, 0.27, 0.09, and 0.04 for 1,2-DCl, 1,1-HCl, 1,2-DF, and 1,1-HF elimination, respectively. Electronic structure calculations were used to define models of the four transition states. The statistical rate constants calculated from these models were compared to the experimental rate constants. The assigned threshold energies with ±2 kcal mol(-1) uncertainty are 60, 72, 65, and 74 kcal mol(-1) for the 1,2-DCl, 1,1-HCl, 1,2-DF, and 1,1-HF reactions, respectively. The loose structure of the 1,1-HX transition states, which is exemplified by the order of magnitude larger pre-exponential factor relative to the 1,2-HX elimination reactions, compensates for the high threshold energy; thus, the 1,1-HX elimination reaction rates can compete with the 1,2-HX elimination reactions for high levels of vibrational excitation in CD3CHFCl. The 1,1-HCl and 1,1-HF reactions are observed via the CD2═CDF and CD2═CDCl products formed from isomerization of the CD3CF and CD3CCl carbenes. These D-atom migration reactions are discussed, and the possibility of tunneling is evaluated. The transition states developed from the 1,1-HCl and 1,1-HF reactions of CD3CHFCl are compared to models for the HCl and HF elimination reactions of CHF2Cl, CHFCl2, and CH2FCl.

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Section: Discussionmentioning

confidence: 73%

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

et al. 2015

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Absolute chlorine and hydrogen atom quantum yield measurements in the 193.3 nm photodissociation of CH3CFCl2 (HCFC-141b)

Läuter

Dhanya

Volpp

2003

The Journal of Chemical Physics

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Articles you may be interested inUltraviolet photochemistry of buta-1,3-and buta-1,2-dienes: Laser spectroscopic absolute hydrogen atom quantum yield and translational energy distribution measurementsThe dynamics of chlorine and hydrogen atom formation in the 193.3 nm gas-phase laser photolysis of room-temperature 1,1-dichloro-1-fluoroethane, CH 3 CFCl 2 ͑HCFC-141b͒, were studied by means of the pulsed-laser-photolysis and laser-induced fluorescence ͑LIF͒ ''pump-and-probe'' technique. Nascent ground-state Cl( 2 P 3/2 ) and spin-orbit excited Cl*( 2 P 1/2 ) as well as H( 2 S) atom photofragments were detected under collision-free conditions by pulsed Doppler-resolved laser-induced fluorescence measurements employing narrow-band vacuum ultraviolet probe laser radiation, generated via resonant third-order sum-difference frequency conversion of dye laser radiation in krypton. Using HCl photolysis as a reference source of well-defined Cl( 2 P 3/2 ), Cl*( 2 P 1/2 ), and H atom concentrations, values for the chlorine-atom spin-orbit branching ratio ͓Cl*͔/͓Cl͔ϭ0.36Ϯ0.08, the total chlorine atom quantum yield (⌽ ClϩCl * ϭ1.01Ϯ0.14), and the H atom quantum yield (⌽ H ϭ0.04Ϯ0.01) were determined by means of a photolytic calibration method. From the measured Cl and Cl* atom Doppler profiles the mean relative translational energy of the chlorine fragments could be determined to be E T(Cl) ϭ157Ϯ12 kJ/mol and E T(Cl * ) ϭ165 Ϯ12 kJ/mol. The corresponding average values 0.56 and 0.62 of the fraction of total available energy channeled into CH 3 CFClϩCl/Cl* product translational energy were found to lie between the limiting values 0.36 and 0.85 predicted by a soft impulsive and a rigid rotor model of the CH 3 CFCl 2 →CH 3 CFClϩCl/Cl* dissociation processes, respectively. The measured total chlorine atom quantum yield along with the rather small H atom quantum yield as well as the observed energy disposal indicates that direct C-Cl bond cleavage is the most important primary fragmentation mechanism for CH 3 CFCl 2 after photoexcitation in the first absorption band.

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Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study

Cited by 2 publications

References 18 publications

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

Absolute chlorine and hydrogen atom quantum yield measurements in the 193.3 nm photodissociation of CH3CFCl2 (HCFC-141b)

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Pyrolysis of 1,1-dichloro-1-fluoroethane in the absence and presence of added propene or CCl4: A computer-aided kinetic study

Cited by 2 publications

References 18 publications

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD3CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD3CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

Absolute chlorine and hydrogen atom quantum yield measurements in the 193.3 nm photodissociation of CH3CFCl2 (HCFC-141b)

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Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions

Characterization of the 1,1-HCl Elimination Reaction of Vibrationally Excited CD₃CHFCl Molecules and Assignment of Threshold Energies for 1,1-HCl and 1,2-DCl plus 1,1-HF and 1,2-DF Elimination Reactions