Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH<sub>2</sub>ICl at 206−432 K

Bilde, Merete; Sehested, and J.; Nielsen, Ole John; Wallington, T. J.; Meagher, and R. J.; Mcintosh, Mark E.; Piety, Charles A.; Nicovich, and J. M.; Wine, P. H.

doi:10.1021/jp9717960

Cited by 29 publications

(44 citation statements)

References 30 publications

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“…It is known that Cl atoms react rapidly with CH 2 ICl to produce CH 2 Cl and ICl. 24 In the current investigation of the 248 nm photodissociation of the CH 2 I 2 only a very weak signal of the HI was observed in addition to the strong signals of the CH 2 I radical and I atom.…”

Section: Methodsmentioning

confidence: 45%

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Eskola

Wójcik-Pastuszka

Ratajczak

et al. 2006

Phys. Chem. Chem. Phys.

131

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The kinetics of the reactions of CH2Br and CH2I radicals with O2 have been studied in direct measurements using a tubular flow reactor coupled to a photoionization mass spectrometer. The radicals have been homogeneously generated by pulsed laser photolysis of appropriate precursors at 193 or 248 nm. Decays of radical concentrations have been monitored in time-resolved measurements to obtain the reaction rate coefficients under pseudo-first-order conditions with the amount of O2 being in large excess over radical concentrations. No buffer gas density dependence was observed for the CH2I + O2 reaction in the range 0.2-15 x 10(17) cm(-3) of He at 298 K. In this same density range the CH2Br + O2 reaction was obtained to be in the third-body and fall-off area. Measured bimolecular rate coefficient of the CH2I + O2 reaction is found to depend on temperature as k(CH2I + O2)=(1.39 +/- 0.01)x 10(-12)(T/300 K)(-1.55 +/- 0.06) cm3 s(-1)(220-450 K). Obtained primary products of this reaction are I atom and IO radical and the yield of I-atom is significant. The rate coefficient and temperature dependence of the CH2Br + O2 reaction in the third-body region is k(CH2Br + O2+ He)=(1.2 +/- 0.2)x 10(-30)(T/300 K)(-4.8 +/- 0.3) cm6 s(-1)(241-363 K), which was obtained by fitting the complete data set simultaneously to a Troe expression with the F(cent) value of 0.4. Estimated overall uncertainties in the measured reaction rate coefficients are about +/-25%.

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Section: Methodsmentioning

confidence: 45%

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Eskola

Wójcik-Pastuszka

Ratajczak

et al. 2006

Phys. Chem. Chem. Phys.

131

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“…The negative temperature dependence for an apparently simple abstraction reaction is perhaps surprising, although there is increasing evidence for complex formation in reactions of an electronegative atom with highly polarizable Br and I atoms in a molecule. 36 Rate coefficients were also determined for the termolecular reaction between Br and BrO (k 7 ) (9.1 ( 2.0) × 10 -12 cm 3 molecule -1 s -1 at 235 K, 760 Torr) and for the reaction between Br and Br 2 O 2 (k 12 ) (4 ( 2) × 10 -10 cm 3 molecule -1 s -1 , 222-235 K).…”

Section: Discussionmentioning

confidence: 99%

Kinetics and Mechanism of the BrO Self-Reaction: Temperature- and Pressure-Dependent Studies

et al. 1998

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The flash photolysis/UV absorption technique has been used to study the self-reaction of BrO radicals over the temperature range 222-298 K and the pressure range 100-760 Torr of N 2 or O 2 . Two chemical sources of BrO radicals were used: photolysis of Br 2 in the presence of excess ozone and photolysis of O 2 in the presence of excess Br 2 . The overall rate constant, k 1 , for the BrO self-reaction (defined by -d[BrO]/dt ) 2k 1 [BrO] 2 ) was found to be temperature and pressure independent at T g 250 K, with k 1 ) (2.88 ( 0.20) × 10 -12 cm 3 molecule -1 s -1 . At temperatures below 250 K, k 1 was found to be pressure dependent, due to the emergence of a new termolecular channel of the BrO self-reaction 1c, -1c forming the BrO dimer, Br 2 O 2 (BrO + BrO + M h Br 2 O 2 + M). Channel-specific rate constants were determined for the two bimolecular channels of the BrO self-reaction above 250 K, giving for (1a) (BrO + BrO f 2Br + O 2 ) k 1a ) (5.31 ( 1.17) × 10 -12 exp{(-211 ( 59)/T} cm 3 molecule -1 s -1 and for (1b) (BrO + BrO f Br 2 + O 2 ) k 1b ) (1.13 ( 0.47) × 10 -14 exp{(983 ( 111)/T} cm 3 molecule -1 s -1 . Below 250 K, the overall rate coefficient of the two bimolecular channels is reduced as the dimer forming channel emerges. At 235 and 222 K, rate constants for the formation (k 1c ) and decomposition (k -1c ) of Br 2 O 2 were recorded. Using the values for K 1c , ∆H r for reaction 1c was estimated as -58.6 ( 0.1 kJ mol -1 . A UV absorption spectrum attributed to Br 2 O 2 was also recorded over the wavelength range 300-390 nm. The cross section of the smooth Br 2 O 2 spectrum was found to be 1.2 × 10 -17 cm 2 molecule -1 at 320 nm. These results are rationalized in terms of a mechanism of the BrO self-reaction that shows competition, at low temperatures, between collisional quenching and unimolecular dissociation of an excited BrOOBr* intermediate. The rate constant for the reaction of oxygen atoms with molecular bromine was also determined in the course of these experiments [O + Br 2 f BrO + Br (5)], giving k 5 ) (5.12 ( 1.86) × 10 -13 exp{(989 ( 91)/T} cm 3 molecule -1 s -1 . All errors are 1σ. The atmospheric implications of these results are discussed.

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“…Chlorine atom kinetics as a function of temperature and pressure of N 2 bath gas were studied using the laser flash photolysis (LFP)–resonance fluorescence (RF) technique. The LFP–RF apparatus was similar to those we have employed in a number of previous studies of chlorine atom reactions with atmospheric gases 24–32. A schematic diagram of the apparatus is published elsewhere 33.…”

Section: Experimental Techniquementioning

confidence: 99%

Temperature‐dependent kinetics study of the gas‐phase reactions of atomic chlorine with acetone, 2‐butanone, and 3‐pentanone

Zhao¹,

Huskey²,

Nicovich³

et al. 2008

Int J of Chemical Kinetics

Self Cite

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A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reactions of atomic chlorine with acetone (CH 3 C(O)CH 3 ; k 1 ), 2-butanone (C 2 H 5 C(O)CH 3 ; k 2 ), and 3-pentanone (C 2 H 5 C(O)C 2 H 5 ; k 3 ) as a function of temperature (210-440 K) and pressure (30-300 Torr N 2 ). No significant pressure dependence is observed for any of the reactions studied. Arrhenius expressions (units are 10 −11 cm 3 molecule −1 s −1 ) obtained from the data are k 1 (T) = (1.53 ± 0.19) exp[(−594 ± 33)/T], k 2 (T) = (2.77 ± 0.33) exp[(+76 ± 33)/T], and k 3 (T) = (5.66 ± 0.41) exp[(+87 ± 22)/T], where uncertainties are 2σ and represent precision only. The accuracy of reported rate coefficients is estimated to be ±15% over the entire range of pressure and temperature investigated. The room temperature rate coefficients reported in this study are in good agreement with a majority of literature values. However, the activation energies reported in this study are in poor agreement with the literature values, particularly for 2-butanone and 3-pentanone. Possible explanations for discrepancies in published kinetic parameters are proposed, and the potential role of Cl + ketone reactions in atmospheric chemistry is discussed. C

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Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH₂ICl at 206−432 K

Cited by 29 publications

References 30 publications

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Kinetics and Mechanism of the BrO Self-Reaction: Temperature- and Pressure-Dependent Studies

Temperature‐dependent kinetics study of the gas‐phase reactions of atomic chlorine with acetone, 2‐butanone, and 3‐pentanone

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Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH2ICl at 206−432 K

Cited by 29 publications

References 30 publications

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Kinetics of the reactions of CH2Br and CH2I radicals with molecular oxygen at atmospheric temperatures

Kinetics and Mechanism of the BrO Self-Reaction: Temperature- and Pressure-Dependent Studies

Temperature‐dependent kinetics study of the gas‐phase reactions of atomic chlorine with acetone, 2‐butanone, and 3‐pentanone

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Kinetics and Mechanism of the Gas Phase Reaction of Atomic Chlorine with CH₂ICl at 206−432 K