Structural, electronic, thermodynamical and charge transfer properties of Chloramphenicol Palmitate using vibrational spectroscopy and DFT calculations

The global problem of advancing bacterial resistance to newer drugs has led to renewed interest in the use of Chloramphenicol Palmitate (C27H42Cl2N2O6) [Palmitic acid alpha ester with d-threo-(-),2-dichloro-N-(beta-hydroxy-alpha-(hydroxymethyl)-p-nitrophenethyl)acetamide also known as Detereopal]. The characterization of the three polymorphic forms of Chloramphenicol Palmitate (CPP) was done spectroscopically by employing FT-IR and FT-Raman techniques. The equilibrium geometry, various bonding features, and harmonic wavenumbers have been investigated for most stable form A with the help of DFT calculations and a good correlation was found between experimental data and theoretical values. Electronic properties have been analyzed employing TD-DFT for both gaseous and solvent phase. The theoretical calculation of thermodynamical properties along with NBO analysis has also been performed to have a deep insight into the molecule for further applications.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three polymorphic forms of CPP have been analyzed by FT-IR and FT-Raman spectra. ► Theoretical computations were performed only for form A and compared with experimental. ► The TD-DFT/6-31G method along with IEF-PCM employed for assignment of electronic excitations. ► Molecular electrostatic potential mapping was used to explain the chemical reactivity. ► NBO analysis was performed to elucidate the charge transfer properties.