Molecular structure, vibrational spectra, NBO analysis and molecular packing prediction of 3-nitroacetanilide by ab initio HF and density functional theory

Abstract

Quantum chemical calculations of geometries and vibrational wavenumbers of 3-nitroacetanilide (C8H8N2O3) in the ground state were carried out by using ab initio HF and density functional theory (DFT/B3LYP) methods with 6-31+G* basis set. The -311++G** basis set is also used for B3LYP level. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. Theoretical vibrational spectra of the title compound were interpreted by means of potential energies distributions (PEDs) using MOLVIB program. The theoretical spectrograms for IR spectra of the title compound have been constructed. The shortening of CH bond length and the elongation of NH bond length suggest the existence of weak CH⋯O and NH⋯O hydrogen bonds, which is confirmed by the natural bond orbital analysis. In addition, the crystal structure obtained by molecular mechanics belongs to the P21 space group, with lattice parameters Z=4, a=14.9989Å, b=4.0367Å, c=12.9913Å, ρ=0.998gcm−3.