Molecular structure, vibrational spectroscopic, NBO, HOMO–LUMO and Mulliken analysis of 4-methyl-3-nitro benzyl chloride

The FT-IR and FT-Raman spectra of 4-methyl-3-nitro benzyl chloride (MNBC) molecule have been recorded in the range of 4000–400 cm−1 and 3500–50 cm−1 respectively. The molecular geometry and vibrational frequencies in the ground state are calculated using the DFT/B3LYP method with 6-311+G (d, p) and 6-311++G (d, p) basis sets. The computed values of frequencies are scaled using a suitable scale factor to yield good coherence with the observed values. Most of the modes have wavenumbers in the expected range. The calculated HOMO–LUMO energy gap shows that charge transfer occur within the molecule. NBO analysis has been performed in order to elucidate charge transfers or conjugative interaction, the intra-molecule rehybridization and delocalization of electron density within the molecule. From the result of Mulliken population analysis, it is clear that the substitution of CH2Cl atoms in the aromatic ring leads to a redistribution of electron density. The total energy distribution (TED) has also been calculated for each mode of the vibration of the molecule.

► The vibrational frequencies of the title compound were discussed.
► HOMO and LUMO energy gap explains the eventual charge transfer interaction taking place within the molecule.
► The NBO analysis confirms the ICT formed by the orbital overlap between the orbitals.
► The result of Mulliken population analysis are tabulated.