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Nonstatistical dynamics in thermal reactions of polyatomic molecules
1Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853-1301, USA. bkc1@cornell.edu
Annual Review of Physical Chemistry
|March 31, 2005
Summary
This review covers advanced models for unimolecular reaction rates, highlighting phase-space bottlenecks in gas-phase reactions and nonstatistical dynamics in organic molecules that challenge standard theories.
Area of Science:
- Chemical Kinetics
- Physical Chemistry
- Computational Chemistry
Background:
- Review of post-Rice-Ramsperger-Kassel-Marcus (RRKM) models for unimolecular reaction kinetics.
- Discussion of gas-phase S(N)2 reaction dynamics, emphasizing phase-space bottlenecks.
Purpose of the Study:
- To review experimental and simulation results on thermal reactions of organic molecules.
- To explore deviations from statistical dynamics predicted by RRKM theory.
Main Methods:
- Analysis of unimolecular reaction kinetics using post-RRKM models.
- Examination of gas-phase S(N)2 reaction dynamics.
- Review of experimental and trajectory simulation data for organic molecule reactions.
Main Results:
- Phase-space bottlenecks play a crucial role in gas-phase S(N)2 reaction dynamics.
- Organic molecules exhibit nonstatistical dynamics, with intermediates decaying faster than predicted by RRKM theory.
- Observed phenomena include bimodal or multimodal lifetime distributions.
Conclusions:
- A qualitative model based on transitional region overlaps in molecular phase space explains observed nonstatistical dynamics.
- Current models may need refinement to accurately describe complex reaction pathways and deviations from statistical behavior.
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