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

Kinetic data for aqueous‐phase reactions of sulfate anion radicals (SO) with perfluorocarboxylates (C_nF_2n+1C(O)O^?) are needed to evaluate removal and transformation processes of C_nF_2n+1C(O)O^? species in the environment, but rate constants for the reactions of SO with C_nF_2n+1C(O)O^? (k_n) have been reported only for short‐chain C_nF_2n+1C(O)O^? species (n = 1–3). Since C_nF_2n+1C(O)O^? reacted with SO to form C_mF_2m+1C(O)O^? (m < n), we determined relative rates k_n?1/k_n for the reactions of SO with C_nF_2n+1C(O)O^? (n = 4–7), along with conversion ratios for conversion of C_nF_2n+1C(O)O^? into C_n?1F_2n?1C(O)O^? (α_n) and into C_n?2F_2n?3C(O)O^? (β_n) at 298 K. SO was photolytically generated from S₂O 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/k₁ 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_nF_2n+1O^?), reaction of C_nF_2n+1O^? with H₂O, and fission of the C? C bond of C_nF_2n+1O^?, seemed to determine α_n and β_n. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 735–747, 2009