Theoretical study of the reactions CF3CH2OCHF2 + OH/Cl and its product radicals and parent ether(CH3CH2OCH3) with OH

✍ Scribed by Lei Yang; Jing-Yao Liu; Li Wang; Hong-Qing He; Ying Wang; Ze-Sheng Li

• Publisher: John Wiley and Sons
• Year: 2007
• Tongue: English
• Weight: 603 KB
• Volume: 29
• Category: Article
• ISSN: 0192-8651
• DOI: 10.1002/jcc.20813

✦ Synopsis

Abstract

A dual‐level direct dynamic method is employed to study the reaction mechanisms of CF~3~CH~2~OCHF~2~ (HFE‐245fa2; HFE‐245mf) with the OH radicals and Cl atoms. Two hydrogen abstraction channels and two displacement processes are found for each reaction. For further study, the reaction mechanisms of its products (CF~3~CH~2~OCF~2~ and CF~3~CHOCHF~2~) and parent ether CH~3~CH~2~OCH~3~ with OH radical are investigated theoretically. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the B3LYP/6‐311G(d,p) level. The energetic information along the MEPs is further refined at the G3(MP2) level of theory. For reactions CF~3~CH~2~OCHF~2~ + OH/Cl, the calculation indicates that the hydrogen abstraction from CH~2~ group is the dominant reaction channel, and the displacement processes may be negligible because of the high barriers. The standard enthalpies of formation for the reactant CF~3~CH~2~OCHF~2~, and two products CF~3~CH~2~OCF~2~ and CF~3~CHOCHF~2~ are evaluated via group‐balanced isodesmic reactions. The rate constants of reactions CF~3~CH~2~OCHF~2~ + OH/Cl and CH~3~CH~2~OCH~3~ + OH are estimated by using the variational transition state theory over a wide range of temperature (200–2000 K). The agreement between the theoretical and experimental rate constants is good in the measured temperature range. From the comparison between the rate constants of the reactions CF~3~CH~2~OCHF~2~ and CH~3~CH~2~OCH~3~ with OH, it is shown that the fluorine substitution decreases the reactivity of the CH bond. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008