Formation of pyridine radicals by hydrogen atom abstraction: theoretical study

Specific features of the pyridine structure make it a convenient model system to describe coal combustion; however, the main attention of researchers has been paid to the formation of the ortho-pyridyl, whereas the formation of meta- and para-pyridyls has been yet poorly studied. The rate constants of the formation of three pyridine radicals by hydrogen atom abstraction by another hydrogen atom are compared. The geometry of the reactants is optimized within the framework of the density functional theory with subsequent refinement of single-point energies by the ab initio G3(MP2,CC) hybrid method. The calculations show that the formation of ortho-pyridyl is preferable, though the formation and further transformations of all three radicals should be taken into account for a detailed description of the coal combustion process.