Quenching rate constants for the removal of SO 2 ( 3 B 1 ) by various fluorinated olefins

A competitive technique employing the SO 2 ( 3 B 1 ) photosensitized isomerization of cis ‐C 2 F 2 H 2 to trans ‐C 2 F 2 H 2 in the presence of selected fluorinated olefins has been used at 3712 Å and 22°C to determine the quenching rate constants of the reaction \documentclass{article}\pagestyle{empty}\begin{document}${\rm SO}_{\rm 2} ({}^3B_1){\rm M}\mathop \to \limits^{k_{_4}}$\end{document} removal. With P So 2 = 25.4 torr and P cis ‐ C 2 F 2 H 2 = 0.239 torr Stern–Volmer plots for M = C 2 H 4 , C 2 H 2 F, 1,1‐C 2 F 2 H 2 , C 2 F 4 , and C 3 F 6 yielded k 4 (units of 10 10 l./mole · sec) values of 5.29 ± 0.16, 4.21 ± 0.53, 1.92 ± 0.23, 0.575 ± 0.060, and 0.0335 ± 0.0027, respectively. The results were consistent with the ability of an olefin to quench SO 2 ( 3 B 1 ) being inversely proportional to the polarizability of the olefin's π bond and the effect can be clearly noted as each H atom in C 2 H 4 is individually replaced by an F atom.