Carbon kinetic isotope effect in the reaction CH4+Cl:: a relative rate study using FTIR spectroscopy

The C-12/C-13 kinetic isotope effect in the reaction of methane with chlorine atoms (KIECl12C/13C) was investigated at 298 K using photolysis of static Cl-2/CH4/N-2 miutures, with in-situ analysis of isotopic composition by FTIR absorption spectroscopy. Least squares fitting of composite (CH4)-C-12/(CH4)-C-13 spectra to reference spectra obtained at the same temperature, pressure and resolution enabled the relative (CH4)-C-12:(CH4)-C-13 content to be measured at a high precision. The result obtained was KIECl12C/13C (298 K) = 1.066 +/- 0.002 (2 sigma), in excellent agreement with the single previous experimental determination at this temperature. This result confirms the unexpectedly high fractionation in the title reaction. (C) 1999 Elsevier Science B.V. All rights reserved.