KINETIC-STUDY IN A MICROWAVE-INDUCED PLASMA AFTERGLOW OF THE CU(S-2) ATOM REACTION WITH CH3CL IN THE TEMPERATURE-RANGE 389-853 K

A kinetic study of the reaction [GRAPHICS] has been carried out in a f ast-flow reactor. The gas phase copper atoms were generated using the microwave-induced plasma (MIP) afterglow technique. Atomic absorption spectroscopy at 327.4 nm was used as the detection technique. The infl uence of the experimental parameters such as the hydrogen content, sub limation temperature of CuCl pellet, and reactor pressure on k(1) has been verified. The rate constant k(1) was measured at temperatures bet ween 389 and 853 K, which resulted in the Arrhenius expression k(1) = (1.73 +/- 0.45) x 10(-11) exp(-34.7 +/- 1.2 kJ mol(-1)/RT) cm(3) molec ule(-1) s(-1). Since the Arrhenius plot shows a slight curvature, the values of k(1) were also fitted to the modified Arrhenius equation k(T ) = AT(n) exp(-E/RT). Meaningful kinetic parameters can only be derive d when n is fixed. A value of n = 2.15 was obtained using transition s tate theory combined with ab initio molecular orbital calculations. In that case the activation barrier of the reaction is lowered to 24.8 k J mol(-1). The measured values of k(1) as a function of temperature ca n best be calculated over the 389-853 K range by the expression log k( 1)(T)= -21.22 - 10.99(log T) + 3.30(log T)(2).