Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction Page: 9,014
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The Journal of Physical Chemistry A
Figure 4 compares the present experimental data for
overall rate with results from literature, as well as with5e-11
3e-114)
E
E
U-le-11
8e-12
6e-12
4e-12
2e-12the
theTemperature (K)
Figure 4. Plot of the temperature dependence of the overall rate
constant for the reaction of NH2 with NO2. "This Work" denotes the
present theoretical rate constant, while "Present" denotes the
experimental results obtained in the present study. Literature data:
Glarborg, Song, Xiang, Pagsberg,9 Whyte,'6 Hack,' Bulatov,'8
and Kurosawa.
theoretical rate constant discussed in the next section. The
present measurements are in close accord with the results of
Kurosawa and Lesclaux who employed a similar pulsed-
photolysis LIF technique's over a range of temperatures, and
there is good agreement with the room temperature LIF data of
Whyte and Phillips'6 and Xiang et al.'7 The LIF results from
Hack et al.14 lie a factor of 2-4 below other studies, and
apparently, some unrecognized interference was present. By
contrast to the present LIF work, experiments based on optical
absorption should not be sensitive to the intensity of the probe
beam, and the results of Bulatov et al.'s and Pagsberg et al.19
agree with the present work at room temperature. The
temperature dependence obtained by Bulatov et al. is somewhatThis Work " Whyte
---Glarborg ---BHack
- --Song ----- Bulatov
x Xian g Kurosawa
Q Pagsberg a Present
40. ....6 -
'.....
40 80 . 12'00 1600' 2000Table 2. Stationary Point Energies for the Reaction of NH2 with NO2a
species
NH2 + NO2
H2NNO2 (1)
H2NONO (2)
trans-HNN(O)OH (3)
cis-HNN(O)OH (4)
H2NO + NO (P1)
H20 + NNO (P2)
trans-HNNO + OH (P3)
cis-HNNO + OH (P4)
3NH + HONO (PS)
(1) - (3)
(3) .-+ (4); bend
(3) .-+ (4); torsion
(4) - (P2)
NH2 + NO2 * (P1)
NH2 + NO2 * (PS)
H2N---N(O)O * H2N---ONOG2(Pu)b
0
-52.0
-34.1
-42.6-13.3
-91.0
9.5
15.0
-12.5
-8.5
-3.4
-5.3CBS-Qc
-30.9
-40.9
-40.7-12.3
-14.9
-10.7RQCISD(T)/CBS
0
-50.40
-31.70
-41.47
-41.30
-15.35
-90.96
5.46
11.33
14.16
-12.58
-15.68
-10.87
-10.81
32.10
22.09HL
0
-49.90
-30.80
-41.04
-40.78
-14.35
-90.55
4.93
11.20
14.31
-11.62
-14.67
-9.96
-10.26PT2/CBS
0-1.13
"All energies include zero-point corrections and are in kcal/mol relative to NH2 + NO2. bFrom Mebel et al.26 cFrom Ploeger et al.5 using the
present H2NNO2 HL result as a reference since they do not provide the energy of NH2 + NO2.dx.doi.org/10.1021 /jp4068069 I J. Phys. Chem. A 2013, 117, 9011-9022
more negative than measured here, leading to a difference of
about a factor of 1.5 at 600 K.
Theoretical. As discussed in the Introduction, the NH2
radical can add to either the N or 0 atoms in NO2 to form
H2NNO2 or H2NONO, respectively. Glarborg et al.'3
presumed that these pathways were unconnected, while
Mebel et al.26 found a low lying transition state connecting
the two entrance channel adducts (H2NNO2 and H2NONO).
More recently, Song et al.22 did a master equation analysis of
the reaction, based on a slightly modified version of the
potential energy surface obtained by Mebel et al., with the
overall rate constant adjusted to agree with experiment.
According to their analysis, H2NO + NO are the only
products, in disagreement with a large body of experimental
results.
In the present work, we apply advanced ab initio transition
state theory based master equation methods to the analysis of
the full temperature and pressure dependence of the kinetics. A
key feature of the analysis involves the treatment of the various
barrierless channels involved in the overall kinetics with the
direct variable reaction coordinate (VRC)-TST method,34-37 as
discussed below. To begin, we have recalculated the energies of
the stationary points with two methods. First, we applied the
RQCISD(T)/CBS(QZSZ)//B3LYP/6-311++G(d,p) method.
The complete basis set (CBS) analysis is based on a two-point
1/(1 + 1)4 extrapolation of explicit calculations with Dunning's
cc-pVQZ and cc-pVSZ basis sets.38 Subsequently, we have
obtained higher level (HL) estimates through the combination
of a UCCSD(T)/cc-pVTZ rovibrational analysis with UCCSD-
(T)/CBS(aug-cc-pVQZ',aug-cc-pVSZ') energies, CCSDT(Q)/
cc-pVDZ higher order corrections, CCSD(T,full)/CBS-
(TZ,QZ) core-valence corrections, CI/aug-cc-pcVTZ relativ-
istic corrections, HF/cc-pVTZ diagonal Born-Oppenheimer
corrections, and B3LYP/6-311++G(d,p) anharmonic ZPE
corrections This method is closely related to other high level
methods such as the popular HEAT39 and W440 methods, for
example.
The anharmonic ZPE correction is calculated as the
difference between spectroscopic perturbation theory and9014
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Klippenstein, Stephen J.; Harding, Lawrence B.; Glarborg, Peter; Gao, Yide; Hu, Huanzhen & Marshall, Paul. Rate Constant and Branching Fraction for the NH₂ + NO₂ Reaction, article, August 22, 2013; [Washington, D.C.]. (https://digital.library.unt.edu/ark:/67531/metadc488184/m1/4/?rotate=90: accessed April 23, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT College of Arts and Sciences.