Structural, spectral analysis of ambroxol using DFT methods

The FT-IR and FT-Raman spectra of Ambroxol are recorded in the region 4000-450 cm−1 and 4000-50 cm−1 respectively. Theoretical calculations were performed by density functional theory (DFT) method using 6-31G(2d,3p) basis set. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to the simulated spectra of the title compound, which show excellent agreement with the observed spectra. The frontier orbital energy gap and dipole moment, illustrates the high reactivity of the title molecule. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analysed using natural bond orbital (NBO) analysis. Molecular electrostatic potential (MEP), the electronic properties were performed by time-dependent DFT (TD-DFT) approach, and HOMO-LUMO energy levels are also constructed.