Rate constants and conversion ratios for aqueous-phase reactions of SO with CnF2n+1C(O)O− (n = 4–7) at 298 K

✍ Scribed by Shuzo Kutsuna; Kazuhide Koike; Hisao Hori

• Publisher: John Wiley and Sons
• Year: 2009
• Tongue: English
• Weight: 386 KB
• Volume: 41
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20448

✦ Synopsis

Abstract

Kinetic data for aqueous‐phase reactions of sulfate anion radicals (SO) with perfluorocarboxylates (C~n~F~2__n__+1~C(O)O^−^) are needed to evaluate removal and transformation processes of C~n~F~2__n__+1~C(O)O^−^ species in the environment, but rate constants for the reactions of SO with C~n~F~2__n__+1~C(O)O^−^ (k~n~) have been reported only for short‐chain C~n~F~2__n__+1~C(O)O^−^ species (n = 1–3). Since C~n~F~2__n__+1~C(O)O^−^ reacted with SO to form C~m~F~2__m__+1~C(O)O^−^ (m < n), we determined relative rates k~n−1~/k~n~ for the reactions of SO with C~n~F~2__n__+1~C(O)O^−^ (n = 4–7), along with conversion ratios for conversion of C~n~F~2__n__+1~C(O)O^−^ into C~n−1~F~2__n__−1~C(O)O^−^ (α~n~) and into C~n−2~F~2__n__−3~C(O)O^−^ (β~n~) at 298 K. SO was photolytically generated from S~2~O by use of sunlamps (λ ≈ 310 nm). Even if k~n~ and k~n−1~ change with increasing ionic strength, k~n−1~/k~n~ can be determined when k~n−1~/k~n~ and α~n~ remain almost constant during the reaction. The values of k~n~/k~1~ for n = 4–7 were nearly equal, and their average was 0.82 ± 0.04 (2σ). Conversion ratios of α~n~ and β~n~ were mostly independent of n for n = 4–7, and their averages were 0.77 ± 0.07 (2σ) and 0.13 ± 0.08, respectively. Branching ratios of reactions of a possible intermediate (C~n~F~2__n__+1~O^•^), reaction of C~n~F~2__n__+1~O^•^ with H~2~O, and fission of the CC bond of C~n~F~2__n__+1~O^•^, seemed to determine α~n~ and β~n~. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 735–747, 2009