Gaseous reaction mechanism of C 2 F radical with water

The kinetic properties of the carbon–fluorine radicals are little understood except those of CF n ( n =1–3). In this article, a detailed mechanistic study was reported on the gas‐phase reaction between the simplest π‐bonded C 2 F radical and water as the first attempt to understand the chemical reactivity of the C 2 F radical. Various reaction channels are considered. The most kinetically competitive channel is the quasi‐direct hydrogen‐abstraction route forming P 5 HCCF + OH. At the CCSD(T)/6‐311+G(2d,2p)//B3LYP/6‐311G(d,p)+ZPVE, CCSD(T)/6‐311+G(3df,2p)//QCISD/6‐311G(d,p)+ZPVE and Gaussian‐3//B3LYP/6‐31G(d) levels, the overall H‐abstraction barriers (4.5, 4.7, and 4.2 kcal/mol) for the C 2 F + H 2 O reaction are comparable to the corresponding values (5.5, 3.7, and 5.7 kcal/mol) for the analogous C 2 H + H 2 O reaction. This suggests that C 2 F is a reactive radical like the extensively studied C 2 H, in contrast to the situation of the CF and CF 2 radicals that have much lower reactivity than the corresponding hydrocarbon species. Thus, the C 2 F radical is expected to play an important role in the combustion processes of the carbon–fluorine chemistry. Furthermore, addition of a second H 2 O can catalyze the reaction with the H‐abstraction barrier significantly reduced to a marginally zero value (0.5 kcal/mol). This is also indicative of the potential relevance of the title reactions in the low‐temperature atmospheric chemistry. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 363–367, 2006