Picturing the transition-state region and understanding vibrational enhancement for the Cl + CH4 → HCl + CH3 reaction

Journal of Physical Chemistry

Volumn 100, Issue 19, 1996, Pages 7938-7947

  Simpson, William R ^a   Rakitzis, T Peter ^a   Kandel, S Alex ^a   Lev On, Topaz ^a   Zare, Richard N ^a  

^a STANFORD UNIVERSITY   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

EID: 33747291168     PISSN: 00223654     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp952627n     Document Type: Article

References (34)

1. Levine, R. D.; Bernstein, R. B. Molecular Reaction Dynamics and Chemical Reactivity; Oxford University Press: New York, 1987.
2. Morrison, R. T.; Boyd, R. N. Organic Chemistry, 5th ed.; Allyn and Bacon: Boston, 1987.
3. Simpson, W. R.; Orr-Ewing, A. J.; Zare, R. N. Chem. Phys. Lett. 1993, 272, 163-171.
4. Simpson, W. R.; Orr-Ewing, A. J.; Kandel, S. A.; Rakitzis, T. P.; Zare, R. N. J. Chem. Phys. 1995, 103, 7299-7312.
5. Simpson, W. R.; Rakitzis, T. P.; Kandel, S. A.; Orr-Ewing, A. J.; Zare, R. N. J. Chem. Phys. 1995, 103, 7313-7335.
6. Atkinson, R.; Baulch, D. L.; Cox, R. A.; Hampson, R. F., Jr.; Kerr, J. A.; Troe, J. J. Phys. Chem. Ref. Data 1992, 21, 1125-1168.
7. Truong, T. N.; Truhlar, D. G.; Baldridge, K. K.; Gordon, M. S.; Steckler, R. J. Chem. Phys. 1989, 90, 7137-7142.
8. Dobbs, K. D.; Dixon, D. A. J. Phys. Chem. 1994, 95, 12584-12589.
9. Wang, X.; Ben-Nun, M.; Levine, R. D. Chem. Phys. 1995, 797, 1-17.
10. Duncan, W. T.; Truong, T. N., submitted.
11. Shafer, N. E.; Orr-Ewing, A. J.; Simpson, W. R.; Xu, H.; Zare, R. N. Chem. Phys. Lett. 1993, 272, 155-162.
12. Kinsey, J. L. J. Chem. Phys. 1977, 66, 2560.
13. Hall, G. E. In Twelfth Combustion Research Conference; The Combustion Research Facility of Sandia National Laboratory: Livermore, CA, 1990; p 122.
14. Aoiz, F. J.; Brouard, M.; Enriquez, P. A.; Sayos, R. J. J. Chem. Soc., Faraday Trans. 1993, 89, 1427-34.
15. Kim, H. L.; Wickramaaratchi, M. A.; Zheng, X.; Hall, G. E. J. Chem. Phys. 1994, 101, 2033-2050.
16. Shafer-Ray, N. E.; Orr-Ewing, A. J.; Zare, R. N. J. Phys. Chem. 1995, 99, 7591.
17. Polanyi, J. C.; Wong, W. H. J. Chem. Phys. 1969, 51, 1439.
18. Polanyi, J. C. Acc. Chem. Res. 1972, 5, 161.
19. Aquilanti, V.; Cappellitti, D.; Pirani, R. J. Chem. Soc., Faraday Trans. 1993, 89. 1467-1474.
20. Sinha, A.; Hsiao, M. C.; Crim. F. F. J. Chem. Phys. 1990, 92, 6333-4.
21. Sinha, A.; Hsiao, M. C.; Crim, F. F. J. Chem. Phys. 1991, 94, 4928-35.
22. Bronikowski, M. J.; Simpson, W. R.; Girard, B.; Zare, R. N. J. Chem. Phys. 1991, 95, 8647-8648.
23. Bronikowski, M. J.; Simpson, W. R.; Zare, R. N. J. Phys. Chem. 1992, 97, 2194-2203.
24. Bronikowski, M. J.; Simpson, W. R.; Zare, R. N. J. Phys. Chem. 1992, 97, 2204-2208.
25. Sinha, A.; Thoemke, J. D.; Crim, F. F. J. Chem. Phys. 1992, 96, 372-6.
26. Gueuler, R. D.; Jones, G. C., Jr.; Posey, L. A.; Zare, R. N. Science 1994, 266, 259-261.
27. Chiu, Y.; Fu, H.; Huang, J.; Anderson, S. L. J. Chem. Phys. 1994, 101, 5410-5412.
28. Chiu, Y.; Fu, H.; Huang, J.; Anderson, S. L. J. Chem. Phys. 1995, 102, 1199-1216.
29. Metz, R. B.; Thoemke, J. D.; Pfeiffer, J. M.; Crim, F. F. J. Chem. Phys. 1993, 99, 1744-51.
30. The reaction of atomic chlorine with methane shows positive curvature in its Arrhenius plot (that is increased reactivity at high temperature compared to extrapolation of low-temperature data). This behavior leads to larger A factors and higher activation energies at high temperature. The use of a higher A factor would increase the steric factor reported here, but expressions employing a higher A factor also have a larger activation energy. Specifically, the high-temperature rate expression of Clyne and Walker (Clyne, M. A. A.; Walker, R. F. J. Chem. Soc., Faraday Trans. 1973, 69, 1547) includes a steric factor 5 times larger than used here, but it also predicts no reactivity at our collision energy because its barrier height is larger than the present study's collision energy. Therefore, we feel that the use of low-temperature A factors to predict the steric factor is reasonable in this study. It is interesting to note that in this study we find translational energy is less effective in promoting reaction than vibrational energy. Therefore, extrapolation of low-temperature data, where the translational barrier is primarily probed (because of low populations of vibrationally excited states of methane), should underestimate the high-temperature rate, for which both vibration and translation increase reactivity.
31. Andresen, P.; Luntz, A. C. J. Chem. Phys. 1980, 72, 5842-5850.
32. Luntz, A. C.; Andresen, P. J. Chem. Phys. 1980, 71, 5851-5856.
33. The reaction of atomic fluorine with methane also appears to show this behavior of low rotational excitation (see: Agrawalla, B. S.; Setser, D. W. In Gas-Phase Chemiluminescence and Chemi-ionization; Fontijn, A., Ed.; Elsevier Science Publishers, BV: Amsterdam, 1985; p 157).
34. van der Zande, W. J.; Zhang, R.; Zare, R. N.; McKendrick, K. G.; Valentini, J. J. J. Phys. Chem. 1991, 95, 8205-8207.