Synthetic routes and vibrational analysis of 5-(4-Chlorophenyl) -3H-pyrazol-3-one molecule: Raman, Infrared and DFT calculations

•A reaction mechanism has been suggested for synthesis of 5-(4-chlorophenyl) -3H-pyrazol-3-one (CPP) based on molecular orbitals interactions.•IR and Raman spectra of 5-(4-chlorophenyl) -3H-pyrazol-3-one (CPP) recorded.•DFT at B3LYP/6–31G(d) level, (FMO), (MEP) and (NBO) analysis were carried out.•Confident vibrational interpretations were given based on NCA and global reactivity descriptors were also calculated.