1. 1 Effect of Halogenation on the Mechanism of the Atmospheric Reactions between Methylperoxy Radicals and NO. A computational 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

2. 2 Abstract CH 3 O 2 + 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. The intermediate in this reaction is CHX 2 OONOcp, CHX 2 OONOtp, and CHX 2 ONO 2. The latter one would be decomposed to CX 2 O + HONO and CHXO + XNO 2. Halogenation stabilizes CHX 2 OONO and increases exothermicity in the overall reaction that is CHX 2 O 2 + NO →CHX 2 O + NO 2 suggests that halogenation enhances the reactivity. They also discussed the ambiguous issue of CHX 2 OONO ↔ CHX 2 ONO 2 one-step isomerization and found triplet transition state in this reaction.

3. 3 Outline Introduction Computational Methods Results and Discussion -RO 2 + NO → RO + NO 2 -ROONOtp ← → RONO 2 Isomerization Conclusions

4. 4 Introduction In Troposphere RO 2 ∙ + NO ∙ → ROONO → RO ∙ + NO 2 ∙ RO 2 ∙ + NO ∙ → RONO 2 Experiment in 298K (cm 3 mol -1 s -1 ) CF 3 O 2 ∙ + NO ∙ k=1.6x10 -11 CHCl 2 O 2 ∙ + NO ∙ k=1.9x10 -11 CHBr 2 O 2 ∙ + NO ∙ k=1.1x10 -11 CH 3 O 2 ∙ + 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: Pasadena, CA, 2006. Sehested, J.; Nielsen, O. J.; Wallington, T. J. Chem. Phys. Lett. 1993, 213, 457 Reduction of the RO-O bond strength

5. 5 Introduction Computational Studies CHCl 2 O 2 is more reactive related to CH 3 O 2 + NO RO 2 + NO → ROONO RO 2 + NO → RONO 2 R = alkyl group ROONO ← → RONO 2 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 Zhao, Y.; Houk, K. N.; Olson, L. P. J. Phys. Chem. A 2004, 108, 5864

6. 6 Computational method Method Geometry and vibrational frequencies ： (U)MP2 、 (U)B3LYP Single-point energies ： CCSD(T) Mutilevel ： G2(MP2) 、 G3//B3LYP Basis set 6-311++G(d,p) Program Gaussian 03

7. 7 Results and Discussion The Mechanism of CHX 2 O 2 + NO CHX 2 O 2 + NO → CHX 2 OONO → CHX 2 O + NO 2 CHX 2 ONO 2 → CHX 2 O + NO 2 CHX 2 ONO 2 → CX 2 O + HONO CHX 2 ONO 2 → CHXO + XNO 2 The Halogenation X = H 、 F 、 Cl

8. 8 Energy profile CHX 2 O 2 +NO CHX 2 OONOcp CHX 2 OONOtp TS cp-tp CHX 2 O+NO 2 G3//B3LYP

9. 9 -MP2 -B3LYP (halogenated methyl peroxynitrite)

10. 10 Results and Discussion a Relative energy (kcal/mol) respect to CHX 2 O 2 + NO b The energy including zero-point energy

11. 11 Energy profile CHCl 2 O 2 +NO CHCl 2 OONOcp CHCl 2 OONOtp TS cp-tp CHCl 2 O+NO 2 CHCl 2 ONO 2 CClHO+ClNO 2 CCl 2 O+HONO TS ccl 2 o TS cclho G3//B3LYP

12. 12 (halogenated methyl nitrate) -MP2 -B3LYP

13. 13 Energy profile CHCl 2 O+NO 2 CHCl 2 ONO 2 TS ccl 2 o TS cclho CClHO+ClNO 2 CCl 2 O+HONO CHF 2 O+NO 2 CHF 2 ONO 2 TS cf 2 o TS cfho CFHO+FNO 2 CF 2 O+HONO G3//B3LYP

14. 14 Results and Discussion a Relative energy (kcal/mol) respect to CHX 2 O 2 + NO b The energy include zero-point energy

15. 15 Experimental Results (IR spectra) Chiappero, M. S.; Burgos Paci, M. A.; Arg ello, G. A.; Wallington, T. J. Inorg. Chem. 2004, 43, 2714 CHF 2 O 2 NO 2 + hυ→ CHF 2 ONO 2 CHF 2 ONO 2 → CFHO + FNO 2 CHF 2 ONO 2 (80 ± 10% ) CFHO (10~20% )

16. 16 Results and Discussion Bond distances (Å)

17. 17 Results and Discussion ROONOtp ←→ RONO 2 Experimental results RO 2 + NO → RONO 2 RO 2 + NO → RO + NO 2 ← → RONO 2 (low pressure) Computational results RO 2 + NO → ROONO → RO + NO 2 → RONO 2 (low pressure) RO 2 + NO → ROONOtp ←→ RONO 2 (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

18. 18 B3LYP/6-311++(d,p) Potential Energy Curve 2006

19. 19 Results and Discussion a Relative energy (kcal/mol) respect to CHX 2 O 2 + NO b The energy including zero-point energy

20. 20 Experimental Result At near room temperature and 1atm, CF 3 O 2 + NO produce at least 3 times more CX 3 ONO 2 than CH 3 O 2 + NO. CF 3 O 2 k(nitrate) / k(total) = (1.67±0.27)x10 -2 CH 3 O 2 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

21. 21 Conclusions The increased reactivity is attributed to the more stable CHX 2 OONO intermediates and the larger exothermicity of the overall reaction CHX 2 O 2 + NO → CHX 2 O + NO 2 compared to CH 3 O 2 + NO → CH 3 O + NO 2. CHX 2 ONO 2 formation is suggested that the singlet CHX 2 OONO and singlet CHX 2 ONO 2 isomerization, through the triplet transition state. The computational results are in agreement with some experimental results.

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