Quantum chemical reactivity indices for sulfonamides by density functional theory (DFT)

Antibiotics have been mostly used in human, livestock and agriculture. Sulfonamides (SA) are important class of antibiotics in the world because of their properties such as low cost, low toxicity and effective against bacterias that are the source of many diseases. SAs are used in therapeutic agents against specific bacterias which cause some diseases like urinary, skin and respiratory track infections. As a consequence of extensive usage most of the SAs and their metabolites released into into the environment. SA residues are frequently detected in water due to the their water soluable property. As a result, the presence of SAs in the environment, threatens human health. So, it is important to calculate some of chemical indices in order to predict toxicity of these compounds. In this study, 22 SA molecules were modeled for both gas and aqueous phases. Conformational analyses and geometry optimizations of all the structures were performed to determine the most stable structures. Modeling of the molecules was performed with DFT at B3LYP/6-311++G(d,p) level. The solvation effects were calculated by using CPCM as the solvation model. As a result of quantum chemical calculations, the quantum chemical indices of SA molecules were calculated. The quantitative structure activity relationships, (QSAR's) expressing the toxicity value in terms of the quantum chemical indices were derived by using linear regression for SA molecules.The correlations between the experimental toxicity values and the calculated quantum chemical indices were examined.