Energetics of the O{sup {minus}} + CH{sub 4} ion-molecule reaction
Journal Article
·
· Bulletin of the American Physical Society
OSTI ID:127902
- and others
The reaction of O{sup {minus}} with CH{sub 4} is exothermic by 24.9 kJ/mol to form OH{sup {minus}} through hydrogen abstraction. Preliminary experimental data indicate that the rate of this reaction is substantially reduced by the substitution of deuterated methane. The authors have examined the minimum energy pathway for this reaction, along the {sup 2}A{sub 1} ground state surface, using the intrinsic reaction coordinate method of Schmidt, et al. At the HF/6-31++G(d,p) level of theory, they find a classical barrier height of approximately 2 kJ/mol. Rovibrational energy quantum corrections have been applied to reactants, transition states and products for CH{sub 4} and the deuterated forms CH{sub 2}D{sub 2} and CD{sub 4}. The calculated barrier heights and overall exothermicity correlate with the observed relative reaction rates for the deuterated forms; an increased barrier height results in a slower rate for D abstraction compared to H abstraction. Correlated energy calculations at the MP2/6-31++G(d,p) level of theory have been carried out for reactants, products and at the geometry of the transition state. The effect of correlation is to lower the barrier heights uniformly. The authors find a broad barrier along the minimum energy reaction coordinate in the region of the transition state. This suggests that quantum tunneling effects are negligible for this system.
- OSTI ID:
- 127902
- Report Number(s):
- CONF-920376--; CNN: Contract F49620-89-C-0019
- Journal Information:
- Bulletin of the American Physical Society, Journal Name: Bulletin of the American Physical Society Journal Issue: 9 Vol. 37; ISSN BAPSA6; ISSN 0003-0503
- Country of Publication:
- United States
- Language:
- English
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