On April 6^th, 2017, the Research Group of Laboratory of Molecular Science with the first author, Mr. Mai Van Thanh Tam has just published a research named “Kinetics of Thermal Unimolecular Decomposition of Acetic Anhydride - An Integrated Deterministic and Stochastic Model” on The Journal of Physical Chemistry A (IF 2.883)
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Acetic anhydride, (CH₃CO)₂O can be considered as an acetylating reagent that thermally decomposes to give ketene and acetic acid, (CH₃CO)₂O →  CH₂CO + CH₃COOH. This reaction has truly received considerable interest for the purpose to produce ketene (CH₂CO), an important intermediate in the combustion of hydrocarbon fuels. Despite its importance, only a few kinetic investigations concerning the title reaction have been studied both experimentally and theoretically. Therefore, his group applied an integrated deterministic and stochastic model, within the master equation/Rice–Ramsperger– Kassel–Marcus (ME/RRKM) framework (via the Multi-Species Multi-Channels (MSMC) code developed at ICST) (Minh v. Duong et al., Int. J. Chem. Kinet., 2015, 47(9), 564-575), which was first used to characterize temperature- and pressure dependent behaviors of thermal decomposition of acetic anhydride in a wide range of conditions. Particularly, using potential energy surface and molecular properties obtained from high-level electronic structure calculations at CCSD(T)/CBS, macroscopic thermodynamic properties and rate coefficients of the title reaction were derived with corrections for hindered internal rotation and tunneling treatments.
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Being in excellent agreement with the scattered experimental data, the results from deterministic and stochastic frameworks confirmed and complemented each other to reveal the main decomposition pathway proceeds via a 6-membered-ring transition state with the 0-K barrier of 35.2 kcal×mol^-1. This observation was further understood and confirmed by the sensitivity analysis on the time-resolved species profiles and the derived rate coefficients with respect to the ab initio barriers. Such an agreement suggests the integrated model can be confidently used for a wide range of conditions as a powerful post-facto and predictive tool in detailed chemical kinetic modeling and simulation for the title reaction and thus can be extended to complex chemical reactions.
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Graphical abstract

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Author: Thanh Tam
Editor: Kim Loan