Structural And Molecular Changes Of Isonicotinylhydrazine Anti-Tubercular Drug In Alcohol Environment: An Intuition From Theory

Isonicotinylhydrazine (INH) also known as isoniazid was attached with alcohol active group at C1, C2, C4, C5 and N atoms to form INHOH1, INHOH2, INHOH4, INHOH5 and INHOHN molecules. From our result, we observed that absorption wavelength of INH was extended remarkably, 295 nm and 547 nm in INHOH2 and INHOHN respectively. C=C stretching vibrations was observed at 1604.88 cm-1, 1618.98 cm-1, 1601.69 cm-1, 1607.23 cm-1, 1621.00 cm-1 and 1652.89cm-1 for INH, INHOH1, INHOH2, INHOH4, INHOH5 and INHOHN respectively. NH2 bending vibrations was observed at 1686.55 cm-1, 1686.55 cm-1, 1683.04cm-1, 1688.49 cm-1, 1685.26 cm-1 and 1676.35 cm-1 for INH, INHOH1, INHOH2, INHOH4, INHOH5 and INHOHN respectively. C=O stretching vibrations for INH was observed at 1778 91 cm-1 while for INHOH1, INHOH2, INHOH4, INHOH5 and INHOHN it was observed at 1777.07 cm-1, 1732.58 cm-1, 1769.27 cm-1, 1781.81 cm-1, 1732.57 cm-1, respectively. Quantum chemical descriptors calculation shows that interaction of OH with INH lowered its energy gap in all molecules with the lowest energy gap (0.131 eV) observed for INHOHN which suggests high interaction and reactivity. Natural bond orbital (NBO) analysis reveals that transition from π*-π* had major contribution to electron transition. The positive binding energies calculated for the different molecules were 317. 988 Kcal/mol, 315.633 Kcal/mol, 321.002 Kcal/mol, 319.036 Kcal/mol and 2.0877 Kcal/mol for INH, INHOH1, INHOH2, INHOH4, INHOH5 and INHOHN respectively. The positive binding energies show that alcohol binding to isoniazid is less favourable.