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Thermal Dissociation and Roaming Isomerization of Nitromethane: Experiment and Theory
- Source :
- The journal of physical chemistry. A. 119(28)
- Publication Year :
- 2015
-
Abstract
- The thermal decomposition of nitromethane provides a classic example of the competition between roaming mediated isomerization and simple bond fission. A recent theoretical analysis suggests that as the pressure is increased from 2 to 200 Torr the product distribution undergoes a sharp transition from roaming dominated to bond-fission dominated. Laser schlieren densitometry is used to explore the variation in the effect of roaming on the density gradients for CH3NO2 decomposition in a shock tube for pressures of 30, 60, and 120 Torr at temperatures ranging from 1200 to 1860 K. A complementary theoretical analysis provides a novel exploration of the effects of roaming on the thermal decomposition kinetics. The analysis focuses on the roaming dynamics in a reduced dimensional space consisting of the rigid-body motions of the CH3 and NO2 radicals. A high-level reduced-dimensionality potential energy surface is developed from fits to large-scale multireference ab initio calculations. Rigid body trajectory simulations coupled with master equation kinetics calculations provide high-level a priori predictions for the thermal branching between roaming and dissociation. A statistical model provides a qualitative/semiquantitative interpretation of the results. Modeling efforts explore the relation between the predicted roaming branching and the observed gradients. Overall, the experiments are found to be fairly consistent with the theoretically proposed branching ratio, but they are also consistent with a no-roaming scenario and the underlying reasons are discussed. The theoretical predictions are also compared with prior theoretical predictions, with a related statistical model, and with the extant experimental data for the decomposition of CH3NO2, and for the reaction of CH3 with NO2.
- Subjects :
- Nitromethane
Thermal decomposition
Molecular physics
Dissociation (chemistry)
chemistry.chemical_compound
chemistry
Ab initio quantum chemistry methods
Computational chemistry
Potential energy surface
Master equation
Physics::Chemical Physics
Physical and Theoretical Chemistry
Roaming
Shock tube
Subjects
Details
- ISSN :
- 15205215
- Volume :
- 119
- Issue :
- 28
- Database :
- OpenAIRE
- Journal :
- The journal of physical chemistry. A
- Accession number :
- edsair.doi.dedup.....6a3ffd776457a978fda28f87a721f767