Rate Constants for the Reactions I + OClO, I + ClO, Cl + I<sub>2</sub>, and Cl + IO and Heat of Formation of IO Radicals

Bedjanian, Yuri; Bras, and Georges Le; Poulet, G.

doi:10.1021/jp960696b

Cited by 27 publications

(36 citation statements)

References 18 publications

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“…Table 2 gives heats of formation for the halogen nitrates, as well as X-O, X-ONO 2 , and XO-NO 2 bond strengths and lowpressure rate coefficients (k 0 ) for formation of the halogen nitrates. It is seen that the ratio of the 7,20,[46][47][48][49][50] This is consistent with the best available estimate for ∆H f°f or IONO 2 of <9.5 kcal/mol, which is obtained from the observation 45 of a rapid reaction between I 2 and NO 3 (see Table 2). Theoretical values for k 0 can be obtained from the statistical adiabatic channel model (SACM) method.…”

Section: Heat Of Formation For Bronosupporting

confidence: 85%

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

and

Tyndall

1996

J. Phys. Chem.

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Rate coefficients (k -7 ) for the thermal decomposition of bromine nitrate, BrONO 2 + M f BrO + NO 2 + M, have been obtained at temperatures between 320 and 340 K and pressures between 100 and 1000 Torr. These data are combined with recommended values for the reverse reaction to obtain an equilibrium constant for the reaction pair, K P,7 ) 5.44 × 10 -9 exp(14192/T) atm -1 , and a heat of reaction for the thermal dissociation of 28.2 ( 1.5 kcal/mol at 298 K. This reaction enthalpy is used in conjunction with literature data to arrive at a consistent set of ∆H f°( 298 K) data for BrONO 2 (10.1 ( 2.0 kcal/mol), BrO (30.4 ( 2.0 kcal/mol), HOBr (-14.1 ( 2.0 kcal/mol), and Br 2 O (27.3 ( 2.0 kcal/mol). Additional measurements were made to determine the rate coefficient for Br atom reaction with BrONO 2 (k 11 ) relative to the rate coefficient for its reaction with CH 3 CHO (k 12 ) at 298 K: k 11 /k 12 ) 12.5 ( 0.6. This relative rate measurement yields a rate coefficient of (4.9 ( 1.5) × 10 -11 cm 3 molecule -1 s -1 for k 11 , using the currently recommended value for k 12 . Approximate rate constants for reaction of NO (reaction 17) and BrNO (reaction 19) with BrONO 2 were also obtained: k 17 ) 3 × 10 -19 cm 3 molecule -1 s -1 , k 19 > 1 × 10 -16 cm 3 molecule -1 s -1 . IntroductionThe role of bromine in the destruction of ozone in the earth's stratosphere is now well characterized. 1-5 Free bromine atoms are released from the destruction of source compounds such as CH 3 Br and the halons and participate in catalytic ozone depleting cycles such as the following:

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Section: Heat Of Formation For Bronosupporting

confidence: 85%

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

and

Tyndall

1996

J. Phys. Chem.

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“…3 shows the thermochemistry of computed here ClIO x together with information for other ClÈIÈO species (Table 4). 16,17,19,20 The solid lines connect species that can be interconverted by breaking or making one bond, i.e., without complex rearrangements. Transition states have not been characterized and therefore some of the exothermic pathways could be blocked by signiÐcant barriers.…”

Section: Resultsmentioning

confidence: 99%

Computational studies of the isomers of ClIO and ClIO2 Implications for the stratospheric chemistry of iodine

Misra¹,

Marshall²

1997

Faraday Trans.

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The geometries of three ClIO isomers and Ðve isomers have been computed at the MP2 \ fc/6-311 ] G(3df ) level of ClIO 2 theory. MP2 \ full/6-31G(d) vibrational frequencies were computed. Gaussian-2 energies and isodesmic reactions were employed to derive for ClIO, ClOI, IClO, ClOIO, ClOOI, IOClO and of 74.7, 82.5, 172.4, 17.0, 113.5, 132.0, 159.9 * f H 298 ClIO 2 , IClO 2 and 189.8 kJ mol~1, respectively. These results were used to assess likely products of the IO ] ClO reaction : there are both indirect pathways to via bound intermediates, and a direct path via abstraction. The other products which are exother-I ] ClO 2 mic and capable of being formed without complex rearrangements are ClOIO, ClOOI and OClOI.

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“…It can also be noted that the concentration of BrCl is not affected by side reactions, for example, with organic radicals formed in reaction (1), since they are rapidly removed by Br 2 , which is present in the reaction system in high concentrations. Finally, Cl atoms were detected also at m / z = 162/164 (ICl + ) upon their titration with an excess of I 2 ([ I 2 ] = (1.0‐1.5) × 10 13 molecule cm −3 , added in the end of the reactor (Figures S1 and S2, Supporting Information) 27 :

\begin{matrix} true \\ left normalCl + I_{2} \to ICl + I \\ left k_{4} = (2.1 \pm 0.3) \times 10^{- 10} {cm}^{3} {molecule}^{- 1} s^{- 1} (T = 296 - 365 K) . \end{matrix}

…”

Section: Methodsmentioning

confidence: 99%

Temperature‐dependent rate constants for the reactions of chlorine atom with methanol and Br₂

Bedjanian

2020

Int J of Chemical Kinetics

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Kinetics of the reaction of Cl atoms with methanol has been investigated at 2 Torr total pressure of helium and over a wide temperature range 225-950 K, using a discharge flow reactor combined with an electron impact ionization quadrupole mass spectrometer. The rate constant of the reaction Cl + CH 3 OH → products (1) was determined using both absolute measurements under pseudo-first order conditions, monitoring the kinetics of Cl-atom consumption in excess of methanol and relative rate method, k 1 = (5.1 ± 0.8) × 10 −11 cm 3 molecule −1 s −1 , and was found to be temperature independent over the range T = 225-950 K. The rate constant of the reaction Cl + Br 2 → BrCl + Br (3) was measured in an absolute way monitoring Cl-atom decays in excess of Br 2 : k 3 = 1.64 × 10 −10 exp(34/T) cm 3 molecule −1 s −1 at T = 225-960 K (with conservative 15% uncertainty). The experimental data for k 3 can also be adequately represented by the temperature independent value of k 3 = (1.8 ± 0.3) × 10 −10 cm 3 molecule −1 s −1 . The kinetic data from the present study are compared with previous measurements. K E Y W O R D SBr 2 , CH 3 OH, Cl, kinetics, rate coefficient 310

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Rate Constants for the Reactions I + OClO, I + ClO, Cl + I₂, and Cl + IO and Heat of Formation of IO Radicals

Cited by 27 publications

References 18 publications

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

Computational studies of the isomers of ClIO and ClIO2 Implications for the stratospheric chemistry of iodine

Temperature‐dependent rate constants for the reactions of chlorine atom with methanol and Br₂

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Rate Constants for the Reactions I + OClO, I + ClO, Cl + I2, and Cl + IO and Heat of Formation of IO Radicals

Cited by 27 publications

References 18 publications

Rate Coefficients for the Thermal Decomposition of BrONO2and the Heat of Formation of BrONO2

Rate Coefficients for the Thermal Decomposition of BrONO2and the Heat of Formation of BrONO2

Computational studies of the isomers of ClIO and ClIO2 Implications for the stratospheric chemistry of iodine

Temperature‐dependent rate constants for the reactions of chlorine atom with methanol and Br2

Contact Info

Product

Resources

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Rate Constants for the Reactions I + OClO, I + ClO, Cl + I₂, and Cl + IO and Heat of Formation of IO Radicals

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

Rate Coefficients for the Thermal Decomposition of BrONO₂and the Heat of Formation of BrONO₂

Temperature‐dependent rate constants for the reactions of chlorine atom with methanol and Br₂