A Study of the Effect of Light on the Structural and Electronic Properties of Propylene Glycol.

In this study, the structural, electronic, optical, and spectroscopic properties of propylene glycol in its liquid state were investigated by using ethanol as a solvent. The analysis was conducted through Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT), employing the B3LYP functional in combination with the 6-311+G-(d,p) basis set. Calculations were performed using Gaussian 09 and GaussView 6.0 software, chosen for their high reliability and accuracy in molecular modeling. Optimized geometries of propylene glycol in both the ground state (prior to light exposure) and the excited state (following light exposure) were obtained to identify structural changes induced by photoexcitation, including variations in bond lengths and bond angles. The electronic properties were subsequently calculated to assess the chemical reactivity of the molecule. Furthermore, infrared (IR) and ultraviolet-visible (UV-Vis) spectra were simulated and compared with the experimental data. The strong agreement between theoretical and experimental results confirms the validity and reliability of the computational approach employed.