Thermochemical and Kinetic Analysis on the Reactions of Neopentyl and Hydroperoxy-Neopentyl Radicals with Oxygen: Part I. OH and Initial Stable HC Product Formation

Abstract

Thermochemical properties for reactants, intermediates, products, and transition states in the neopentyl radical + O2 reaction system are analyzed with ab initio and density functional calculations to evaluate reaction paths and kinetics for neopentyl oxidation. Enthalpies of formation (ΔHf°298) are determined using isodesmic reaction analysis at the CBS-Q composite and density functional levels. The entropies (S°298) and heat capacities Cp(T) (0 ≤ T/K ≤ 1500) from vibrational, translational, and external rotational contributions are calculated using statistical mechanics based on the vibrational frequencies and structures obtained from the density functional study. Potential barriers for the internal rotations are calculated at the B3LYP/6-31G(d,p) level, and hindered rotational contributions to S°298 and Cp(T)'s are calculated by using direct integration over energy levels of the internal rotation potentials. The kinetic analysis on reactions of neopentyl with O2 is performed using enthalpies at the CBS...