Spectroscopic (FT-IR and FT-Raman) studies, NBO, HOMO–LUMO, NMR analyses and thermodynamics functions of 5-bromo-2-methoxybenzaldehyde

Abstract

The (FT-IR and FT-Raman) spectral properties of 5-bromo-2-methoxybenzaldehyde (BMB) are studied using density functional theory (DFT) employing B3LYP/6-311++G (d) and B3LYP/6-311++G (d,p) levels of theory. There are four conformers, C1, C2, C3, and C4 for this molecule. The computational results diagnose the most stable conformer of BMB as the C1 form. The optimized geometrical parameters obtained by B3LYP/6-311++G (d,p) method show good agreement with experimental X-ray data. A study on the electronic properties, such as HOMO and LUMO energies, is performed. The isotropic chemical shift computed by 1H and 13C nuclear magnetic resonance (NMR) chemical shifts of the BMB calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations. The MEP surface reflects the chemical reactivity of a molecule. The thermodynamic functions (heat capacity, internal heat energy, Gibbs energy and entropy) from spectroscopic data by statistical methods were obtained for the range of temperature 100–1000K. The energetic behavior of the compound in different solvent medium (water, ethanol, and methanol) was examined by applying polarizable continuum model (PCM). The complete molecular orbital simulations and theoretical UV–visible spectra carried out in this study yield better understanding of charge delocalization pattern and stability of the title molecules to a greater extent.