Possible reaction pathways of the acetamiprid molecule according to the DFT calculation method

Abstract

Acetamiprid, the major active ingredient of some pesticides, is a subclass of the neonicotinoid group and is used especially against whitefly, aphididae, leaf bugs, potato bugs which affect products such as cotton, tobacco, potato, tomato, nut, citrus, planted in greenhouses and fields. Quantum chemical calculations of density functional theory (DFT) were used to investigate the structural and physical characteristics of acetamiprid. The analysis was made on the probable reaction path of acetamiprid molecule with OH radicals. The calculation of the optimized geometry and the geometric optimization for determination of the lowest energy status were made by the Gauss View 5 and the Gaussian 09 program. Activation energy for the probable reaction paths was calculated and its most stable states from the thermodynamic perspective were determined for the different phases. The aim of this study is to estimate the degradation mechanism of acetamiprid molecule in gaseous phase, in ethanol and water as polar solvents, and in chloroform as a partially polar solvent, all of which were analysed through the conductor-like screening solvation model (COSMO) as the solvation model. The probable reaction path of the activation energy was calculated, and its most stable state in the thermodynamic frame was determined for these phases. © 2018 Bulgarian Academy of Sciences, Union of Chemists in Bulgaria.