Spectroscopic (FT-IR, FT-Raman and UV-vis) investigation and frontier molecular orbitals analysis on 3-methyl-2-nitrophenol using hybrid computational calculations.

In the present study, the FT-IR and FT-Raman spectra of 3-methyl-2-nitrophenol (C(7)H(7)O(3)N) (3M2NP) have been recorded in the range of 4000-100 cm(-1). The fundamental modes of vibrational frequencies of 3M2NP are assigned. All the geometrical parameters have been calculated by HF and DFT (LSDA and B3LYP) methods with 6-31G(d,p) and 6-311G(d,p) basis sets. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values for phenol and some substituted phenol. The harmonic and anharmonic vibrational wave numbers, IR intensities and Raman activities are calculated at the same theory levels used in geometry optimization. The calculated frequencies are scaled and compared with experimental values. The scaled vibrational frequencies at LSDA/B3LYP/6-311G(d,p) seem to coincide with the experimentally observed values with acceptable deviations. The impact of substitutions on the benzene structure is investigated. The molecular interactions between the substitutions (OH, CH(3) and NO(2)) are also analyzed. A detailed interpretation of the infrared spectra of was also reported more precisely. Charge transfer occurring in the molecule between HOMO and LUMO energies, frontier energy gap are calculated and presented. On the basis of the thermodynamic properties of the title compound at different temperatures have been calculated, revealing the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H) and temperatures.