Vibrational spectra and theoretical calculations (dimerization, UV-Vis, multinuclear NMR and pes analyses) of 3,4-dimethylbenzamide and 3,4,5-trihydroxybenzamide.

The FT-IR and FT-Raman spectra of 3,4-dimethyl benzamide (DMBA) and 3,4,5-trihydroxy benzamide (THBA) have been measured in the regions 400-4000 and 50-3500 cm(-1), respectively. Utilizing the observed FT-IR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the title compounds were carried out. The vibrational frequencies which were determined experimentally are compared with those theoretical frequencies from force field calculation based on B3LYP/6-311++G(d,p) methods. Stability of the compound arising from hyperconjugative interactions and charge delocalization have been analyzed using natural bond orbital analysis. UV-Vis analysis of the title compounds has also been done using TD-DFT method. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the compounds were calculated by the gauge independent atomic orbital (GIAO) method and compared with experimental results. HOMO-LUMO and MEP analyses have been done for the title compounds.