Kinetics and thermochemistry of the gas-phase reactions of 4-ethylpyridine with OH radical: A DFT study

The gas-phase reaction between 4-ethylpyridine and OH radical are studied using the hybrid density functional model MPWB1K and BB1K methods. Thermochemistry and kinetic parameters for both addition and hydrogen abstraction reaction from all the potential sites are considered. Barrier heights for all the possible addition and abstraction processes are calculated to identify the most reactive reaction channels in different temperature. The hydrogen abstraction reaction is found to be the dominant reaction channel at higher temperature (>300 K). The calculated total rate constant value (1.1 × 10−12 cm3 molecule−1 s−1) at 298 K for the 4-ethylpyridine + OH reaction obtained from the MPWB1K method is in reasonably good agreement with the available experimental value (3.9 × 10−12 cm3 molecule−1 s−1). DFT-based reactivity descriptors are used to rationalize the observed reactivity trend from kinetic study.