Complete falloff curves for the unimolecular decomposition of i-propoxy radicals between 330 and 408 K

Abstract

The temperature and pressure dependence of the rate constant for the unimolecular decomposition of i-propoxy radicals has been determined using the laser photolysis/laser induced fluorescence technique. Important features of the potential energy surface have been calculated by abinitio methods. Experiments have been performed at total pressures between 0.01 and 60 bar of helium and in the temperature range 330–408 K. The low and the high pressure limiting rate constants have been extracted from a complete falloff analysis: k₀=[He]×1.0×10^-8 exp(-43.8 kJ mol^-1/RT) cm³ s^-1 and k_∞=1.2×10¹⁴ exp(-63.7 kJ mol^-1/RT) s^-1. We estimate an uncertainty for these rate constants of ±30%. Both rate constants have been discussed in terms of statistical unimolecular rate theory. Very good agreement between the calculated and the experimental rate constants has been found.