Molecular Structural, Spectral and HOMO-LUMO Analysis of Acemetacin in Aqueous Phases: A Density Functional Theory Study

Polar and non-polar solvents like water (ε = 78.5), ethanol (ε = 24.852), acetone (ε = 20.493) and diethyl ether (ε = 4.24) were employed to study the solubility of acemetacin, which is a non-steroidal anti-inflammatory drug (NSAID) through quantum density functional theoretical studies using B3LYP/6-31G(d) level. In present study, acemetacin was optimized in the gaseous phase and further explored in the solution phase environments. The characteristic parameters of acemetacin such as bond lengths, bond angles, total energy, dipole moment, thermal energies, specific heat, entropy and zero point vibrational energy in gaseous and solution phases were computed. The energy difference between most stable [acemetacin in water (AMN-W)] and the least stable structure [acemetacin in diethyl ether (AMN-D)] was found to be 3.76 Kcal/mol. The zero point vibrational energy of acemetacin in gas phase is found to be 225.05 Kcal/mol. The fundamental vibrational frequency analysis of acemetacin has been done by using B3LYP/6-31G(d) level and compared with the harmonic vibrational frequencies. The HOMO-LUMO analysis of acemetacin has also been investigated. The molecular electrostatic potential (MEP) map was applied to study the distribution of charge density and the location of the chemical reactivity of acemetacin.