Kinetics and Dynamics of Cyclopentanone Thermal Decomposition in Gas Phase.

Cyclopentanone is a potential bio-fuel which can be produced from bio-mass. Its gas phase dissociation chemistry has attracted several experimental and theoretical investigations. In the photochemical and thermal decomposition studies of cyclopentanone, ethylene and carbon monoxide were found to be dominant reaction products along with several other compounds in smaller quantities. For the formation of ethylene and carbon monoxide, a concerted mechanism has been proposed as the primary reaction pathway. In addition, a step-wise mechanism involving ring-opened radical intermediate has also been considered. The present work reports gas phase thermal decomposition of cyclopentanone at high temperatures investigated using electronic structure theory methods, Rice-Ramsperger-Kassel-Marcus (RRKM) rate constant calculations, and Born-Oppenheimer direct classical trajectory simulations. The trajectory calculations were performed on density functional PBE96/6-31+G* potential energy surface using initial conditions selected from fixed energy normal mode distributions. Simulations showed that ethylene and carbon monoxide formed primarily via the concerted mechanism confirming the earlier predictions. In addition, step-wise pathways were also observed for the same products in lower fraction of trajectories. Furthermore, several other reaction products in smaller quantities and new mechanistic pathways were observed. The computed RRKM rate constants and simulation data are in agreement with experimental results and detailed atomic level dissociation mechanisms presented.