1 effect of halogenation on the mechanism of the atmospheric reactions between methylperoxy radicals...
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Effect of Halogenation on the Mechanism of the Atmospheric Reactions between Methylperoxy Radicals and NO. A computa
tional Study
作者: Agnie M. Kosmas*†, Zoi Salta†, and Antonija Lesar‡出處: J. Phys. Chem. A, 2009, 113 (15), pp 3545–3554 指導教授:胡維平 教授報告學生:彭家瑜報告日期: 2010/03/29
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Abstract
CH3O2 + NO reaction had been discussed in experimental and
computational studies. The authors wanted to study the influence of halogenation about this reaction by using ab initio and DFT method. T
he intermediate in this reaction is CHX2OONOcp, CHX2OONOtp, an
d CHX2ONO2. The latter one would be decomposed to CX2O + HON
O and CHXO + XNO2. Halogenation stabilizes CHX2OONO and incr
eases exothermicity in the overall reaction that is CHX2O2 + NO →C
HX2O + NO2 suggests that halogenation enhances the reactivity. They
also discussed the ambiguous issue of CHX2OONO ↔ CHX2ONO2 o
ne-step isomerization and found triplet transition state in this reaction.
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Outline
IntroductionComputational Methods
Results and Discussion
-RO2 + NO → RO + NO2
-ROONOtp ←→ RONO2 Isomerization
Conclusions
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Introduction
In Troposphere RO2∙+ NO∙→ ROONO → RO∙+ NO2∙
RO2∙+ NO∙→ RONO2
Experiment in 298K (cm3mol-1s-1) CF3O2∙+ NO∙ k=1.6x10-11
CHCl2O2∙+ NO∙k=1.9x10-11
CHBr2O2∙+ NO∙k=1.1x10-11
CH3O2∙+ NO∙ k=7.7x10-12
Sander, S. P.; Friedl, R. R.; Golden, D. M.; Kurylo, M. J.; Moortgat, G. K.; Wine, P. H.; Ravishankara, A. R.; Kolb, C. E.; Molina, M. J.; Finlayson-Pitts, B. J.; Huie, R. E.; Orkin, V. L.Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies: Evaluation Number 15. JPL Publication 06-2; National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Insitute of Technology: Pa
sadena, CA, 2006.
Sehested, J.; Nielsen, O. J.; Wallington, T. J. Chem. Phys. Lett. 1993, 213, 457
Reduction of the RO-O bond strength
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Introduction
Computational Studies CHCl2O2 is more reactive related to CH3O2 + NO
RO2 + NO → ROONO RO2 + NO → RONO2 R = alkyl group
ROONO ←→ RONO2 isomerization
King, M. D.; Thomson, K. C. Atmos. Environ. 2003, 37, 4517
Lohr, L. L.; Barker, J. R.; Stroll, R. M. J. Phys. Chem. A 2003, 107, 7429
Zhao, Y.; Houk, K. N.; Olson, L. P. J. Phys. Chem. A 2004, 108, 5864
Barker, J. R.; Lohr, L. L.; Stroll, R. M.; Reading, S. J. Phys. Chem. A 2003, 107, 7434
Zhang, J.; Dransfield, T.; Donahue, N. M. J. Phys. Chem. A 2004, 108, 9082
Zhang, J.; Dransfield, T.; Donahue, N. M. J. Phys. Chem. A 2004, 108, 9082
Zhao, Y.; Houk, K. N.; Olson, L. P. J. Phys. Chem. A 2004, 108, 5864
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Computational method
Method Geometry and vibrational frequencies : (U)MP2 、 (U)B3LY
P
Single-point energies : CCSD(T)
Mutilevel : G2(MP2) 、 G3//B3LYP
Basis set 6-311++G(d,p)
Program Gaussian 03
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Results and Discussion
The Mechanism of CHX2O2 + NO
CHX2O2 + NO → CHX2OONO → CHX2O + NO2
CHX2ONO2 → CHX2O + NO2
CHX2ONO2 → CX2O + HONO
CHX2ONO2 → CHXO + XNO2
The Halogenation X = H 、 F 、 Cl
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Energy profile
-35
-30
-25
-20
-15
-10
-5
0
kca
l/mol
X=H
X=Cl
X=F
CHX2O2+NO
CHX2OONOcpCHX2OONOtp
TS cp-tp
CHX2O+NO2
G3//B3LYP
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-MP2-B3LYP
(halogenated methyl peroxynitrite)
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Results and Discussion
a Relative energy (kcal/mol) respect to CHX2O2 + NO b The energy including zero-point energy
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11-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
kcal
/mol
X=Cl
Energy profileCHCl2O2+NO
CHCl2OONOcp CHCl2OONOtp
TS cp-tpCHCl2O+NO2
CHCl2ONO2
CClHO+ClNO2
CCl2O+HONO
TS ccl2o
TS cclho
G3//B3LYP
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(halogenated methyl nitrate)
-MP2-B3LYP
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13-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
kcal
/mol
X=Cl
X=F
Energy profile
CHCl2O+NO2
CHCl2ONO2
TS ccl2o
TS cclho
CClHO+ClNO2
CCl2O+HONO
CHF2O+NO2
CHF2ONO2
TS cf2o
TS cfho
CFHO+FNO2
CF2O+HONO
G3//B3LYP
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Results and Discussion
a Relative energy (kcal/mol) respect to CHX2O2 + NO b The energy include zero-point energy
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Experimental Results (IR spectra)
Chiappero, M. S.; Burgos Paci, M. A.; Arg ello, G. A.; Wallington, T. J. Inorg. Chem. 2004, 43, 2714
CHF2O2NO2 + hυ→ CHF2ONO2
CHF2ONO2 → CFHO + FNO2
CHF2ONO2 (80 ± 10% )
CFHO (10~20% )
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Results and DiscussionBond distances (Å)
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Results and Discussion
ROONOtp ←→ RONO2
Experimental results
RO2 + NO → RONO2
RO2 + NO → RO + NO2 ←→ RONO2 (low pressure)
Computational results
RO2 + NO → ROONO → RO + NO2 → RONO2 (low pressure)
RO2 + NO → ROONOtp ←→ RONO2 (moderate & high pressure)
Arey, J.; Aschmann, S. M.; Kwok, E. S. C.; Atkinson, R. J. Phys. Chem. A 2001, 105, 1020
Lesar, A.; Hodo ek, M.; Drougas, E.; Kosmas, A. M. J. Phys. Chem. A 2006, 110, 7898
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18B3LYP/6-311++(d,p)
Potential Energy Curve
2006
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Results and Discussion
a Relative energy (kcal/mol) respect to CHX2O2 + NO b The energy including zero-point energy
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Experimental Result At near room temperature and 1atm, CF3O2 + NO produce at le
ast 3 times more CX3ONO2 than CH3O2 + NO.
CF3O2
k(nitrate) / k(total) = (1.67±0.27)x10-2
CH3O2
k(nitrate) / k(total) ≤ 0.5x10-2
Nishida, S.; Takahashi, K.; Matsumi, Y.; Chiappero, M.; Arg ello, G.; Wallington, T. J.; Hurley, M. D.; Ball, J. C. Chem. Phys. Lett. 2004, 388, 242
Results and Discussion
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Conclusions
The increased reactivity is attributed to the more stable CHX2OONO intermediates and the larger exothermicity of the overall reaction CHX2O2 + NO → CHX2O + NO2 compared to CH3O2 + NO → CH3O + NO2.
CHX2ONO2 formation is suggested that the singlet CHX2OONO and singlet CHX2ONO2 isomerization, through the triplet transition state.
The computational results are in agreement with some experimental results.
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