The reaction between ethyl and molecular oxygen II: Further analysis

The present investigation is a rather substantial extension and elaboration of our previous work on the same reaction. In this article we accomplish four primary objectives: 1. We show quantitatively how sensitive the high‐temperature rate coefficient k (T) is to E 02 , the threshold energy of the transition state for direct molecular elimination of HO 2 from ethylperoxy radical (C 2 H 5 O 2 ), thus deducing a value of E 02 =−3.0 kcal/mol (measured from reactants). 2. We derive the result that k 0 (T) ≈ k ′ ∞ (T) in the high‐temperature regime, where k 0 (T) is the zero‐pressure rate coefficient, and k ′ ∞ (T) is the infinite‐pressure rate coefficient for the bimolecular channel. 3. Most importantly, we discuss the three different regimes of the reaction (low‐temperature, transition, and high‐temperature) in terms of the eigenvectors and eigenvalues of G , the transition matrix of the master equation. The transition regime is shown to be a region of avoided crossing between the two chemically significant eigenvalue curves in which the thermal rate coefficient k (T , p ) jumps from one eigenvalue to the other. This jump is accompanied by a “mixing” of the corresponding eigenvectors, through which both eigenvectors deplete the reactant. The onset of the high‐temperature regime is triggered by reaching the “stabilization limit” of the ethylperoxy adduct, a limit that is induced by a shift in equilibrium of the stabilization reaction. Our identification of the prompt and secondary HO 2 formed by the reaction with these eigenvalue/eigenvector pairs leads to good agreement between theory and the experiments of Clifford et al. (J Phys Chem A 2000, 104, 11549–11560). 4. Lastly, we describe the master equation results in terms of a set of elementary reactions and phenomenological rate coefficients. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 732–740, 2001