Nidaa A Jasim , Tahrir G Mjeed

Department of Chemistry, General Directorate of Education, Karbala 56001, Iraq;

For correspondence:-  Nidaa Jasim   Email: nedaa.aljbory@gmail.com

Received: 2 August 2026        Accepted: 16 September 2026        Published: 30 September 2026

Citation: Jasim NA, Mjeed TG. Comparative DFT analysis of sulphadiazine and sulphathiazole: A quantum chemical study of sulphonamide derivatives. Trop J Pharm Res 2026; 25(9):1257-1266 doi: 10.4314/tjpr.v25i9.9

© 2026 The authors.
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Abstract

Purpose: To model the molecular structure and electronic properties of two sulphonamide derivatives, sulphadiazine (SDZ) and sulphathiazole (STZ), using quantum mechanics based on Density Function Theory (DFT) in order to provide theoretical evidence of differences in reactivity and biological activity of the two compounds.

Methods: Quantum mechanics calculations based on DFT were applied to SDZ and STZ. Charge distribution and electron density were calculated using the Kohn-Sham equations. Bond lengths and angles were calculated, and the energy gap was determined by calculating the energy of the two orbitals: the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO). The thermodynamic properties of both drugs, as well as their infrared vibrational frequencies, were also predicted.

Results: The DFT study showed the concentration of electron density around the sulphonyl oxygen of SDZ and STZ, as well as the nitrogen atoms of the pyrimidine ring of SDZ. However, STZ showed higher polarization due to the sulphur- and nitrogen-containing thiazole ring. STZ showed a lower energy gap, indicating higher reactivity and better biological activity than SDZ. STZ also showed lower thermodynamic values than SDZ. The key infrared vibrations showed a high level of similarity for both compounds, although SDZ displayed slightly higher values than STZ.

Conclusion: The findings from this study have provided theoretical evidence in support of the observed differences in the reactivity and effectiveness of SDZ and STZ. The data obtained have laid a strong theoretical foundation for the design of safer and more effective drugs

Keywords: Density Function Theory, Quantum Mechanics, Sulphonamide derivatives, Sulphadiazine, Sulphathiazole

Impact Factor
Thompson Reuters (ISI): 0.6 (2023)
H-5 index (Google Scholar): 49 (2023)