Atmospheric reactions of (H)- and (D)-fluoroalcohols with chlorine atoms.

The reactions of Cl with a series of fluoroalcohols and deuterated fluoroalcohols, CF(3)CH(2)OH (k(4)), CF(3)CH(OH)CH(3) (k(5)), CF(3)CH(OH)CF(3) (k(6)), CF(3)CH(OD)CF(3) (k(7)) and CF(3)CD(OD)CF(3) (k(8)), are investigated as a function of temperature in the range of 268-378 K by laser photolysis-resonance fluorescence. To our knowledge, only the CF(3)CH(2)OH + Cl reaction has been previously studied from a kinetic point of view. The derived Arrhenius expressions obtained using our kinetic data are: k(4) = (1.79+/-0.17) x 10(-13) exp[(410+/-26)/T], k(5) = (1.20+/-0.11) x 10(-12) exp[(394+/-14)/T], k(6) = (2.32+/-0.18) x 10(-13) exp[-(740+/-12)/T], k(7) = (6.45+/-1.87) x 10(-13) exp[-(1136+/-94)/T] and k(8) = (4.19+/-1.09) x 10(-13) exp[-(1378+/-81)/T] (in units of cm(3) molecule(-1) s(-1) and where errors are +/-sigma). Moreover, a theoretical insight into the mechanisms of these reactions is pursued through ab initio Möller-Plesset second-order perturbation treatment calculations with the 6-311G** basis set. Optimized geometries are obtained for reagents, transition states and molecular complexes appearing along the different reaction pathways. Furthermore, molecular energies are calculated at the quadratic configuration interaction with single, double and triple excitations [QCISD(T)] level to obtain an estimation of the activation energies. Finally, the rate constants are calculated through transition-state theory using Wigner's transmission coefficient in order to include the tunnelling-effect corrections.