Studies On The Hydrolysis And Photolysis Of Dinotefuran

Dinotefuran, chemical name:(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furylmethyl)guanidine, is thethird generation of neonicotinoid insecticide developed by Mitsui Chemicals and first registered in Japan.The hydrolysis of nitenpyram under the different pH value and temperatures, and its photolysis in water ororganic solvents were studied in this paper.The impacts of different temperatures (15℃,25℃,35℃,50℃) and different pH valus (5,7,8,9,10) on the hydrolysis of dinotefuran were researched. The results showed that the hydrolysis rate ofdinotefuran could be characterized by first-order kinetics. The hydrolytic rate of dinotefuran was slow inthe aci-dic and neuter solution, but fast in basic solution. The hydrolytic rate of dinotefuran increased withthe increasing temperature，and the average temperature coefficient was2.22. The activation entropyshowed a significantly negative correlation with the temperature, but no obvious correlations between theactivation energy or activation enthalpy to temperature were observed.The results showed that the photolysis rate of dinotefuran could be characterized by first-order kineticsin four organic solvents under UV lamp. The photolysis rate of dinotefuran in four organicsolvents followed the sequence: ethyl acetate> methanol> ethanol> acetone, the photolysis half1ife ofdinotefuran in ethyl acetate, methanol, ethanol and acetone was3.39h,4.83h,5.05h and9.23h, respectively.The results showed that the photolysis rate of dinotefuran could be characterized by first-order kineticsin aqueous solution. The photolytic rate showed negative correclation with the initial concentration ofdinotefuran. In buffer solutions, the photolytic rate increased gradually with the increasing of pH values.The photolytic half-life of dinotefuran in pH5, pH7, pH8and pH9was12.42h,12.06h,10.84and8.45h,respectively. Fe3+and NO3-could enhance photolysis of dinotefuran in aqueous solutions and the reactionrare increased obviously with enhancing the concentration of Iron ions. HA showed optical quenchingeffect on the photolysis of dinotefuran and the optical quenching effect increased with the concentrationenhanced. When the HA concentration was1mg/L,5mg/L and10mg/L, the photolytic half-life ofdinotefuran was10.65h,11.18h and12.43h, and the optical quenching was17.31%,20.48%and34.54%, respectively. Under UV lamp, three surfactants (SDS, CTAB, TBAB) had optical quenching effect on thephotolysis of dinotefuran and the optical quenching effect increased with the concentration enhanced. Incomparison, the optical quenching effect of TBAB and SDS was stronger than CTAB on dinotefuranphptplysis. Besides, in the sunlight and ultraviolet light, the photolysis of dinotefuran in pure water andnatural water were studied. It indicated that in the four water samples, the order of the reaction rate was:groundwater> pure water> pond water> river water.Finally, the hydrolysis and photolysis products of dinotefuran were analysed by using HPLC-MS, andconcluded that the part of the degradation mechanism of dinotefuran.