Theoretical studies on OH and Cl initiated hydrogen atom abstraction of HFE-227pc (CF3OCF2CHF2)

• Published in: Journal of atmospheric chemistry 2013-09, Vol.70 (3), p.257-268
• Main Authors: Singh, Hari Ji, Rao, Pradeep Kumar, Tiwari, Laxmi
• Format: Article
• Language: English
• Subjects: Atmospheric chemistry; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Earth and Environmental Science; Earth Sciences; Hydrogen; Reaction kinetics
• ISSN: 0167-7764; 1573-0662
• DOI: 10.1007/s10874-013-9266-5

The kinetics of hydrogen atom abstraction reactions of HFE-227pc by OH and Cl was studied by ab initio method. The structural optimization and frequency calculation of the titled compound and the species formed during the abstraction reactions were performed with density functional theory using hybrid meta density functional MPWB1K with 6–31 + G(d,p) basis set. The energy of the species was further refined by making a single point energy calculation at G3B3 level of theory. The standard enthalpies of formation of reactant and the radical formed after H-atom abstraction was calculated using isodesmic method. The rate constants of abstraction reactions were calculated using Conventional Transition State Theory (CTST) and were found to be 1.5 × 10 −15 and 0.53 × 10 −16  cm 3 molecule −1 s −1 for OH and Cl respectively. The calculated value for the abstraction by OH is close to the experimental value of 2.26 × 10 −15  cm 3 molecule −1 s −1 whereas the same for Cl is found to be about five times lower than that of 2.70 × 10 −16  cm 3 molecule −1 s −1 . The theoretical studies yielded the enthalpies of formation and the rate constants that are vital in determining the lifetime of HFE-227pc.