Role of Intersystem Crossing in the Dynamics of the O(3P) + C2H5I Reaction

Wang, J. J.; Smith, David J.; Grice, R.

doi:10.1021/jp953703p

Cited by 23 publications

(38 citation statements)

References 20 publications

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“…Neither is obviously flawed, although the authors of the discharge-fast flow study 3 (smaller k 1 value) suggested that the laser photolysis-resonance fluorescence study 2 (larger k 1 value) may have been affected by unrecognized secondary chemistry that consumed OH, even though the latter authors sought such effects by variation of the laser intensity but did not observe systematic changes in k 1 . The present data yield the first Arrhenius parameters for reaction 1, and the A factor found here, around 10 -11 cm 3 molecule -1 s -1 , implies a fairly loose TS and is typical of A factors found for H abstraction reactions by OH from, for example, H 2 or CH 4 . 25 The rate constant at the mean tropospheric temperature of 277 K, estimated from eq 4 to be 4.0 × 10 -14 cm 3 molecule -1 s -1 , is about 5 times that for OH + CH 3 CCl 3 , and thus the tropospheric lifetime of CF 3 I with respect to OH attack is about 0.2 of that of CH 3 CCl 3 , i.e., about 1.5 years.…”

Section: E[g2(mp2)] ) E[qcisd(t)/6-311g(dp)]supporting

confidence: 78%

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI

et al. 1998

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The kinetics of the reaction of hydroxyl radicals with trifluoroiodomethane were investigated by the flash photolysis-resonance fluorescence technique. A rate constant of k ) 5.8 × 10 -12 exp((-11.3 kJ mol -1 )/RT) cm 3 molecule -1 s -1 was measured over the temperature range 280-450 K with accuracy limits of 20% (450 K) to 30% (280 K). Different product channels were investigated by ab initio methods, and the dominant products are CF 3 + HOI. The enthalpy of formation of hypoiodous acid was analyzed with Gaussian-2 theory, in conjunction with G2 energies for INO, ICN, ClCN, and other species. The transition state and reaction coordinate for OH + CF 3 I was characterized at the G2(MP2) level, and the results suggest a negligible barrier to the reverse reaction of CF 3 + HOI, so that the measured forward activation energy can be used to derive ∆ f H 298 (HOI) ) -69.6 ( 5.4 kJ mol -1 . The implications of the kinetics and thermochemistry for iodine chemistry in flames and the atmosphere are discussed, and for the range 280-2000 K a proposed rate expression is k ) 2.9 × 10 -16 (T/K) 1.5 exp(-(960 K)/T) cm 3 molecule -1 s -1 .

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Section: E[g2(mp2)] ) E[qcisd(t)/6-311g(dp)]supporting

confidence: 78%

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI

et al. 1998

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“…[60][61][62] At low initial translational energy, 3.8 kcal mol Ϫ1 , both IO and HOI products from the O͑ 3 P͒ϩC 2 H 5 I reaction emerge from the OIC 2 H 5 complex, as has been shown in crossed molecular beam experiments. 61͑a͒ The formation of the HOI product arises from the OIC 2 H 5 complex through a five-centered ring transition state in which the H atom migrates to the oxygen from the terminal CH 3 group.…”

Section: Vibrational Energy Disposal and Comparison With X؉hbr Himentioning

confidence: 61%

Dynamics of OH and OD radical reactions with HI and GeH4 as studied by infrared chemiluminescence of the H2O and HDO products

Butkovskaya

Setser

1997

The Journal of Chemical Physics

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Articles you may be interested inAccurate combined-hyperbolic-inverse-power-representation of ab initio potential energy surface for the hydroperoxyl radical and dynamics study of O + OH reaction A laser photolysis/time-resolved Fourier transform infrared emission study of OH (X 2 Π,v) produced in the reaction of alkyl radicals with O ( 3 P)The infrared chemiluminescence of vibrationally excited H 2 O and HDO from the highly exothermic reactions of OH and OD radicals with HI and GeH 4 was observed in the 2200-5500 cm Ϫ1 range. The experiments utilized a fast-flow reactor with 0.3-1 Torr of Ar carrier gas at 300 K; the OH͑OD͒ radicals were produced via the H͑D͒ϩNO 2 reaction and the H or D atoms were generated by a discharge in a H 2 ͑D 2 ͒/Ar mixture. The H 2 O and HOD vibrational distributions were determined by computer simulation of the emission spectra in the 2200-3900 cm Ϫ1 range. The total vibrational energy released to H 2 O and HOD molecules is, respectively, ͗ f v ͘ ϭ 0.36 and 0.41 from HI and ͗ f v ͘ ϭ 0.46 and 0.51 from GeH 4 . These values are significantly smaller than for the reactions of OH and OD with HBr, ͗ f v ͘ ϭ 0.61 and 0.65. The populations of the O-H stretching vibration of HOD and the collisionally coupled 1 and 3 stretching modes of H 2 O decrease with increasing vibrational energy. In contrast, the vibrational distribution from the HBr reaction is inverted. The bending mode distributions in all stretching states of H 2 O and HOD extend to the thermodynamic limit of each reaction. A surprisal analysis was made for H 2 O͑HOD͒ distributions from the title reactions and compared with that for OH͑OD͒ϩHBr. The surprisal analysis tends to confirm that the dynamics for the HI and GeH 4 reactions differ from the HBr reaction. The HI reaction may proceed mainly via addition-migration, while the GeH 4 reaction may involve both direct abstraction and addition-migration. A rate constant for the OHϩGeH 4 →H 2 OϩGeH 3 reaction was evaluated by comparing the H 2 O emission intensities with that of the OHϩHBr→H 2 OϩBr reaction, k GeH 4 /k HBr ϭ 6.5 Ϯ 0.9. Secondary kinetic-isotope effects, k OH /k OD ϭ 1.4 Ϯ 0.1, 1.0Ϯ0.2, and 1.3Ϯ0.2, were determined for reactions of OH and OD with GeH 4 , HI, and HBr, respectively, by comparing the relative H 2 O and HOD emission intensities.

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“…31 In the gas phase, IVR is observed in polyatomic molecules at energies where vibrational state densities exceed ϳ10-100 states/cm Ϫ1 . 37 The lifetime of the Br II complex ͑bound by ϳ60 kJ/mol) was ϳ44 ps at a center-ofmass collision energy of 1.7 kJ/mol, dropping to ϳ5 ps and 3 ps for collision energies of 52 kJ/mol and 87 kJ/mol, respectively. Vibrational state densities for these transient ''physisorbed complexes'' consisting of an incident molecule interacting with several surface atoms ͑oscillators͒ are greater than 10 5 states/cm Ϫ1 even at the threshold energy for dissociative chemisorption.…”

Section: A Applicability Of a Statistical Treatment Of Gas-surface Rmentioning

confidence: 96%

Microcanonical unimolecular rate theory at surfaces. II. Vibrational state resolved dissociative chemisorption of methane on Ni(100)

Abbott

Bukoski

Harrison

2004

The Journal of Chemical Physics

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A three-parameter microcanonical theory of gas-surface reactivity is used to investigate the dissociative chemisorption of methane impinging on a Ni(100) surface. Assuming an apparent threshold energy for dissociative chemisorption of E(0)=65 kJ/mol, contributions to the dissociative sticking coefficient from individual methane vibrational states are calculated: (i) as a function of molecular translational energy to model nonequilibrium molecular beam experiments and (ii) as a function of temperature to model thermal equilibrium mbar pressure bulb experiments. Under fairly typical molecular beam conditions (e.g., E(t)>/=25 kJ mol(-1), T(s)>/=475 K, T(n)/=100 K the dissociative sticking is dominated by methane in vibrationally excited states, particularly those involving excitation of the nu(4) bending mode. Fractional energy uptakes f(j) defined as the fraction of the mean energy of the reacting gas-surface collision complexes that derives from specific degrees of freedom of the reactants (i.e., molecular translation, rotation, vibration, and surface) are calculated for thermal dissociative chemisorption. At 500 K, the fractional energy uptakes are calculated to be f(t)=14%, f(r)=21%, f(v)=40%, and f(s)=25%. Over the temperature range from 500 K to 1500 K relevant to thermal catalysis, the incident gas-phase molecules supply the preponderance of energy used to surmount the barrier to dissociative chemisorption, f(g)=f(t)+f(r)+f(v) approximately 75%, with the highest energy uptake always coming from the molecular vibrational degrees of freedom. The predictions of the statistical, mode-nonspecific microcanonical theory are compared to those of other dynamical theories and to recent experimental data.

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Role of Intersystem Crossing in the Dynamics of the O(³P) + C₂H₅I Reaction

Cited by 23 publications

References 20 publications

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI

Dynamics of OH and OD radical reactions with HI and GeH4 as studied by infrared chemiluminescence of the H2O and HDO products

Microcanonical unimolecular rate theory at surfaces. II. Vibrational state resolved dissociative chemisorption of methane on Ni(100)

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Role of Intersystem Crossing in the Dynamics of the O(3P) + C2H5I Reaction

Cited by 23 publications

References 20 publications

Experimental and Computational Investigations of the Reaction of OH with CF3I and the Enthalpy of Formation of HOI

Experimental and Computational Investigations of the Reaction of OH with CF3I and the Enthalpy of Formation of HOI

Dynamics of OH and OD radical reactions with HI and GeH4 as studied by infrared chemiluminescence of the H2O and HDO products

Microcanonical unimolecular rate theory at surfaces. II. Vibrational state resolved dissociative chemisorption of methane on Ni(100)

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Product

Resources

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Role of Intersystem Crossing in the Dynamics of the O(³P) + C₂H₅I Reaction

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI

Experimental and Computational Investigations of the Reaction of OH with CF₃I and the Enthalpy of Formation of HOI