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

Abstract

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.

Rate constant calculations of the GeH4 + OH/OD → GeH3 + H2O/HOD reactions using an ab initio based full-dimensional potential energy surface

“…These are defined in the usual way, as the ratio of the rate constants for the perprotio reaction to the deuterated reaction, GeH 4 + OH/GeH 4 + OD. To the best of our knowledge, only one experimental value has been reported at 298 K, 2 1.4 AE 0.1, which is very similar to the equivalent HBr + OH/OD reaction, 2 1.3 AE 0.2. The calculated KIE at 298 K using the PES-2015 surface are, respectively, 0.80 and 1.37, using VTST and QCT approaches.…”

“…The only experimental evidence is an estimation of zero activation barrier. 2 Depending on the level used, we obtained values from +0.65 to À6.04 kcal mol À1 , with the worst value, À6.04 kcal mol À1 , obtained when relativistic effects were considered. Clearly this does Finally, the intermediate complexes present similar energy stability, regardless of the level used, with differences of about AE1.0 kcal mol À1 .…”

“…To the best of our knowledge, no theoretical studies (kinetics and dynamics) have been reported on this reaction, and only one experimental study is available. 2,3 Butkovskaya and Setser 2,3 studied the infrared chemiluminescence of H 2 O and HOD products in the reactions of OH and OD radicals with germane at 298 K. They found that: (i) about 50% of the available energy is released as H 2 O and HOD product vibrational energy, while the other product, GeH 3 , does not receive much internal energy; (ii) the stretching vibrational distribution was inverted and nearly statistical for the H 2 O and HOD products, respectively; and (iii) the rate constant was determined, (7.1 AE 1.0) Â 10 À11 cm 3 molecule À1 s À1 at 298 K, relative to the well known rate constant for the similar BrH + OH -Br + H 2 O, 1.1 Â 10 À11 cm 3 molecule À1 s À1 , by measuring the integrated water emission intensity from both reactions.…”

Spin–orbit corrected potential energy surface features for the I (2P3/2) + H2O → HI + OH forward and reverse reactions

“…In the same year, Macleod, Balestra, Jourdain, Laverdet, and Le Bras 10 investigated the gas phase reaction of OH radicals with hydrogen iodide via a different LP-RF apparatus, and they determined the rate constant to be (2.7 AE 0.2) Â 10 À11 cm 3 molecule À1 s À1 at 298 K. One year later the HI + OH reaction was examined with discharge-flow reactors coupled to electron paramagnetic resonance (EPR) and mass analysis spectrometry, and the rate constant for this reaction was concluded to be (3.3 AE 0.2) Â 10 À11 cm 3 molecule À1 s À1 at 298 K by Lancar, Mellouki, and Poulet. 11 The reaction of OH radicals with HI was studied by Butkovskaya and Setser 12 in 1997 via analysis of the infrared chemiluminescence in a fast-flow reactor with 0.3-1 Torr of Ar at 300 K. They found that the dynamics for the HI reaction differs from the HBr reaction, with the rate constant being 2.7 Â l0 À11 cm 3 molecule À1 s À1 . Campuzano-Jost and Crowley 13 in 1999 investigated the kinetics of the OH + HI reaction at 246-353 K and 75 AE 1 Torr by the laser-flash photolysis technique combined with resonance fluorescence detection of OH.…”

Time-resolved IR chemiluminescence in gas-phase chemical kinetics

“…. 13 and H 2 O, 14 have been studied by this method. The study of the reactions is complicated by the disturbing effect of fast vibration and rotation relaxation processes.…”