Prediction of nitrobenzene toxicity to the algae (Scenedesmus obliguus) by quantitative structure-toxicity relationship (QSTR) models with quantum chemical descriptors.

In this study, Quantitative structure-toxicity relationship (QSTR) models were developed to predict the toxicity of nitrobenzene to the algae (Scenedesmus obliguus). Quantum chemical descriptors computed by PM3 Hamiltonian were used as predictor variables. The cross-validated Q²(cum) value for the optimal QSTR models is 0.867, indicating good predictive capability. The toxicity of nitrobenzenes (pC) was found to be affected by the molecular structure, the heat of formation (ΔH(f)) and dipole moment (μ(z)). Contrary to the μ(z) values of nitrobenzenes, the ΔH(f) values increase with increase in pC values and the energy of the highest occupied molecular orbital. Increasing the largest positive atomic charge on a nitrogen atom and the most positive net atomic charge on a hydrogen atom of the nitrobenzene leads to decrease in pC values. Nitrobenzenes with larger absolute hardness tend to be more stable and less toxic to the algae.