Theoretical studies on the tautomerism of tetrazole selenone

Abstract

The tautomerism of all possible forms of tetrazole selenone (A-G), induced by proton transfer, was studied, theoretically, in different environments including gas phase, continuum solvent and microsolvated environment with one or two explicit water or ammonia molecules. The calculations were performed using two different levels of theory including mPW2PLYP and DFT-B3LYP. The 6-311++G(d,p) basis set was used for C, H, O and N and the standard relativistic effective core pseudo potential LANL2DZ basis set was used for Se atom. It was found that the tetrazole selenone, in the form of A, is the most stable isomer in all of the environments considered in this work. The kinetics of proton transfer reaction was studied in both gas and solvent environments and it was concluded that the activation energy of the reaction increases with going from the gas phase to polar solvents. Moreover, the proton transfer reaction assisted by one or two water or ammonia molecules was investigated and it was found that the activation energy significantly reduces.

The kinetics of water-assisted tautomeric 1,2-proton transfer in azoles: a computational approach

“…For the tetrazole selenone, the results were similar and 1 water molecule reduced the barrier from 52.8 to 27.3 kcal/mol at the mPW2PLYP/6-311? ?G(d,p) level of theory [31]. The authors considered also the ammonia molecule as a helper, and it follows that it lowered the barrier even more, to 17.4 kcal/mol.…”

“…The preliminary answer from the literature studies can be 2. But the case of 3 water molecules assisting the proton transfer is definitely not fully investigated, there is only 1 paper where only the proton transfer between external group and the ring was studied, but not the 1,2-proton shift in the ring [31]. Therefore, the main aim of the current project is to theoretically model the transition states for 1,2-proton transfer assisted by 1-4 water molecules for fully representative series of azoles: pyrazole, 1,2,4-triazole, 1,2,3-triazole, tetrazole and pentazole in gas phase and in water solution.…”