Quantum-chemical modeling of the stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. A DFT study

The stacking mechanism of the 1H-4H proton transfer in 4-pyridone, 4-pyridinthione and p-aminopyridineare constructed. For quantitative description of this process by means of the quamtumchemicalmethod density functional theory (DFT) the activation energy (<E#), reaction energy (<E)and tautomeric equilibrium constant (KT) has been calculated. The results of calculations have shown,that the values of the energetical and kinetical characteristics, from the point of view of chemicalreactions, in reasonable limits varies, that allows one to make the conclusion in favour of competenceof the offered stacking mechanism for the 1H-4H proton transfer in pyridine derivatives. It is a newone-stage synchronous and unique mechanism for the 1H-4H proton transfer.