Chemically activated systems play an important role in combustion and atmospheric chemistry. The overall reaction paths exhibit complex pressure and temperature dependencies because each intermediate involves a coupled system of competing multistep isomerization, dissociation, and stabilization paths. A number of estimation techniques, exist for deriving the required thermochemical and elementary kinetic input parameters for rate coefficient estimation. The availability of high-level ab initio methods promises to reduce the inaccuracies associated with older empirical methods. The objective of this study is to evaluate the importance of the various thermochemical parameters entering the rate coefficient calculation. We describe and illustrate a computational framework to quantify the functional relationship between the thermochemical properties and the macroscopic observables through appropriate response surface methods. The approach is demonstrated by analyzing the impact of thermochemical properties in estimating autoignition delays in propane oxidation. (c) 2006 American Institute of Chemical Engineers.