CH bond dissociation enthalpies of fluorinated formates and estimation of their rate constants for the reactions with OH radicals: A DFT study

✍ Scribed by Shingo Urata; Tadafumi Uchimaru; Asit K. Chandra; Akira Takada; Akira Sekiya

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 139 KB
• Volume: 34
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.10070

✦ Synopsis

Abstract

Density functional theory was used to estimate the lifetime of fluorinated formates, which are primary products from the oxidation of hydrofluoroethers. First, the CH bond dissociation enthalpies (BDEs) of 10 fluorinated formates, C~n~F~2__n__ + 1~OC(O)H (n = 1–4) and C~n~HF~2__n__~OC(O)H (n = 1–3) have been calculated by using the density functional theory with (RO)B3LYP/6‐311G(d,p). Secondly, from these computed BDEs, the rate constants k~OH~ of the hydrogen abstraction reaction between the fluorinated formates and OH radicals have been estimated using the formulation proposed by Heicklen (Int. J. Chem. Kinet. 13, 651, 1981). We modified the formulation proposed by Heicklen in order to relate BDEs to k~OH~ for formates based on the results of the ab initio studies using standard transition state theory with the G2(MP2) level. Consequently, the k~OH~ of all the formates considered here are estimated to be around 1.5–4.7 × 10^−14^ cm^3^ molecule^−1^ s^−1^ at 298 K. Their lifetimes concerning with the decomposition by OH radicals (τ~OH~) in atmosphere have been evaluated as 0.4–4.5 years from the estimated k~OH~. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 524–530, 2002