Comparison Study of HOMO-LUMO Energy Gaps for Tautomerism of Triazoles in Different Solvents Using Theoretical Calculations

Abstract

The phenomena of the tautomerism forms of the substituted triazoles compounds which are named [1-A] (5-phenyl-1H-1,2,4-triazol-3-amine), [1-B] (3-phenyl-1H-1,2,4-triazol-5-amine), [2-A] (5-(pyridin-2-yl)-1H-1,2,4-triazol-3-amine), [2-B] (3-(pyridin-2-yl)-1H-1,2,4-triazol-5-amine), [3-A] (5-(pyridin-3-yl)-1H-1,2,4-triazol-3-amine), [3-B] (3-(pyridin-3-yl)-1H-1,2,4-triazol-5-amine), [4-A] (5-(pyridin-4-yl)-1H-1,2,4-triazol-3-amine) and [4-B] (3-(pyridin-4-yl)-1H-1,2,4-triazol-5-amine) have been evaluated by Hartree-Fock (HF) method at the basis set (6-31G) in the both gas phase and at different type of solvents. This study of solvents effect was containing polar and non-polar solvent like water, acetone, acetonitrile, benzene and CCl4. The physico-chemical data's were evaluated for eigenvalues at different kinds of energy levels (HOMO, HOMO-1, HOMO-2, HOMO-3, LUMO, LUMO+1, LUMO+2 and LUMO+3). The difference of the energy gap (LUMO-HOMO) values for structures showed that the forms (1A, 2A, 3A and 4A) are more stable compare with (1B, 2B, 3B and 4B). From the results, we can showed that there is a difference between the two forms depends on the parameters. So, the imino form is not stable compare with the other structure.