Structure and Spectroscopy of o -anisidine Investigated by Density Functional Theory in Comparison with Experiments

The molecular structures, vibrational spectra (IR and Raman), UV-Vis electronic absorption spectra, and NMR spectra (13C and 1H) of o-anisidine have been investigated in terms of density functional theory by using B3LYP as a density functional and 6-311++G** as a basis set. Two stable and virtually degenerate conformers arising from non-planarity of the amino group of o-anisidine have been located at the room temperature. All normal modes of o-anisidine have been assigned in terms of percent contributions of the internal motions. All main electronic transitions in the UV-Vis spectrum of o-anisidine have been assigned. Solution that increases ionization potential of o-anisidine but decreases its electron affinity has been shown to affect the unoccupied orbitals of o -anisidine drastically, which shift all electronic absorption bands to longer wavelengths. The frontier molecular orbital, molecular electrostatic potential map, and atomic charge (Mulliken, ESP, and NBO) analyses have been shown useful in estimating both global and atom-in- molecule characteristics of o -anisidine. The present chemical shift calculations allow certain assignments of the experimental 13 C and 1 H NMR signals of o -anisidine. The high correlations between the experimental and the present computational spectral data indicate that the computational route presented in this study can be extended for the spectroscopic calculations of analogous compounds.