An experimental study of the reaction kinetics of C2(X1Σg+) with hydrocarbons (CH4, C2H2, C2H4, C2H6 and C3H8) over the temperature range 24-300 K:: Implications for the atmospheres of Titan and the Giant Planets

The reactivity Of C-2(X-1 Sigma(+)(g)) with simple saturated (CH4, C2H6 and C3H8) and unsaturated (C2H2 and C2H4) hydrocarbons has been studied in the gas phase over the temperature range 24-300 K using the CRESU (Cinetique de Reaction en Ecoulement Supersonique Uniforme or Reaction Kinetics in a Uniform Supersonic Flow) technique. All reactions have been found to be very rapid in this temperature range and the rate coefficients are typically >= 10(-10) cm(3) molecule(-1) s(-1) with the exception of methane for which the rate coefficient is one order of magnitude lower: similar to 10(-11) cm(3) molecule(-1) s(-1). These results have been analyzed in terms of potential destruction sources of C-2(X-1 Sigma(+)(g)) in the atmospheres of Titan and the Giant Planets. It appears that the rate coefficient of the reaction C-1(2) + CH4 should be updated with our new data and that reactions with C2H2, C2H4 and C2H6 should also be included in the existing photochemical models. (c) 2006 Elsevier Inc. All rights reserved.