Theoretical Studies On The Hydrolysis Mechanism Of Dinotefuran

As the third generation of neonicotinoid,dinotefuran has made a significant contribution for modern agriculture,such as the extremely broad insectical spectrum,strong absorption effect,efficient insecticidal activity and unique biochemical properties.Due to its frequent and extensive usage,dinotefuran accumulated in crops and water will lead potential risk to human and animals health,such as chronic poisoning and undermine the normal growth of the crop.Dinotefuran do not contain chlorine atoms and aromatic rings,which is very different from other exist pesticides,therefore,in order to ensure its security,we should pay special attention to the degradation mechanism of dinotefuran in the environment.Some reports indicate that the dinotefuran can be dissolved in organic solvents such as methanol and toluene,and its solubility is even up to 37 g / L.Hydrolysis is one of the primary degradation way of dinotefuran in environment.As far as we know,some experimental studies about the hydrolysis of dinotefuran have been reported in recent years,however,there is no theoretical study on it has been reported and the detailed hydrolysis of dinotefuran still unclear,therefore,it is necessary to study the hydrolysis mechanism of the dinotefuran.The acidity is one of the important factor involving the hydrolysis reaction.In the whole article,we studied the hydrolysis mechanism of the dinotefuran under alkaline,neutral and acidic conditions.We mainly used M06-2X and B3 LYP methods combined with 6-311++G(d,p)basis set and MP2 method combined with 6-311+G(d,p)basis set to calculate.In the gas phase,the geometries structures of the reaction complexes(RC),transition state(TS),intermediate(INT)and product complexes(PC)in all the pathways were fully optimized by M06-2X and B3 LYP methods,respectively.Furthermore,by analyzing the virtual frequency to ensure the authenticity of transition state.In addition,the actual reaction was carried out in aqueous solution,so we should considered the influence of solvation effect on reaction.Therefore,we use conductor-like polarized continuum model(CPCM)reoptimized all the structures in theaqueous solution.The results of computation show that the hydrolysis reaction of dinotefuran under alkaline conditions with the lowest activation energy barrier either in the gas phase or in the aqueous solution.The calculation results show that the hydrolysis of dinotefuran easy to carry out under alkaline conditions in the gas phase or in aqueous solution,the hydrolysis of dinotefuran is alkaline hydrolysis.The optimal path of the hydrolysis is the Path A under alkaline conditions,that is the H6 atoms in the hydroxyl groups of dinotefuran anions migrate to the N2 atom.This study provides a detailed description for the dinotefuran hydrolysis process as well as a further prediction for the further experiments of the dinotefuran,thereby improving the ability and efficiency of the experiment.Our work can provide more reference value for the same type of hydrolysis reaction.