The dark reactions F-2+CF3I, C2F5I, and n-C3F7I

The reactions between F-2 and the lowest members of the homologous series of perfluoroalkyl iodides (CF3I, C2F5I, and n-C3F7I) have been studied. For these compounds, an exponential decrease in the alkyl iodide concentration over time following an induction period is observed for certain experimental conditions. Other conditions; lead to chaotic-like kinetic behavior where the rate of alkyl iodide consumption continually changes. Kinetic rate data with CF3I show that the disappearance rate depends upon both the type of surface and surface preparation. For all three compounds, Arrhenius plots reveal activation energies on the order of 10 kcal/mol, consistent with effective initiation steps of F-2 + RI -->) RIF + F, where R represents the CF3, C2F5, or n-C3F7 radical, respectively. The end products of the F-2 + RI reactions are RF, R(2), and IF5, suggesting that the R radicals play an important kinetic role. Introducing O-2 into the F-2 + RI reaction systems results in successive oxidation of R by O-2, leading to the formation of CF2O as an additional end product. IF(B --> X) emission is observed from the RI-rich F-2 + RI reactions, confirming the existence of IF as an intermediate. (C) 1996 John Wiley & Sons, Inc.