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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

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

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

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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