Study On Chemical Behavior Of Chlorantraniliprole In Aqueous Environment

Chlorantraniliprole belongs to a broad-spectrum and new structure of insecticides known as bisamides/pyrazole class found and developed by Dupont Company. Due to little biological toxicity to non-target, more safety and wider spectrum in applying against insect, chlorantraniliprole has a good application prospects as an alternatives of highly toxic pesticides.At present, research information is very lack on chemical behaviors and biological effects of chlorantraniliprole in the environment. In order to evaluate correctly the environmental safety of chlorantraniliprole, hydrolysis kinetics, photolysis kinetics, photodegradation mechanisms, photodegradation pathways and photoproducts toxicity of chlorantraniliprole were investigated thoroughly, and the effects of aqueous environmental factors on photodegradation of chlorantraniliprole under simulated sunlight was studied in this paper. The results obtained from the experiments are helpful in assessing comprehensively the impact of chlorantraniliprole on the environment.The hydrolysis behavior and the hydrolysis kinetics of insecticide chlorantraniliprole were investigated in aqueous solutions by changing the pH value and temperature in this paper. The results were observed as follows:Hydrolysis of chlorantraniliprole can be described by the first-order kinetics equation. Chlorantraniliprole should be very stable in aqueous solution and the changes in pH and temperature would affect the hydrolysis process of chlorantraniliprole to some extent. Hydrolysis of chlorantraniliprole increased with the increasing pH value of the solution, arid its hydrolysis half-life in the buffer solutions of pH4, pH5,pH6,pH7,pH8,pH9 and pH10 was 141,100,81,66,75,78 and 47d, respectively, suggesting that the hydrolysis rate was faster in basic solution and neutral solution than in acidic solution. Hydrolysis of chlorantraniliprole in the neutral solution increased with the increasing temperature. Hydrolysis half-life was 85,66 and 36d at the temperature of 15℃, 25℃ and 35 ℃, and temperature effect coefficient (Q) was an average of 1.57. The average activation energy (Ea), enthalpy(⊿ H) and entropy (⊿ S) for hydrolysis of chlorantraniliprole was 31.58 kJ/mol,291.05kJ/mol and-182.51kJ/mol·K, respectively. It has no significant correlation between the activation energy and the temperature of hydrolysis reaction, and average activation energy and enthalpy are small. The absolute activation entropy increased with the increased temperature, showing a significant correlation and suggesting that hydrolysis of chlorantraniliprole in aqueous solution should be constrained by the activation entropy.Photodegradation mechanism of insecticide chlorantraniliprole in aqueous solutions was studied under the simulated sunlight in this paper. Quenching experiments demo nstrate that the photodegradation of chlorantraniliprole by simulated sunlight includes direct photolysis and self-sensitized photolysis in the aquatic environment (direct phot odegradation contributed to the main degradation of chlorantraniliprole). Toxicity expe riments showed that the generation of some more toxic products of chlorantraniliprole than chlorantraniliprole in the photolysis process. Five intermediates identified by UP LC/Q-TOF-MS are as follows:2-(2-Bromo-5-oxa-1,9,9b-triaza-cyclopenta[a]naphthalen-4-ylideneamino)-5-chloro-3,N-Dimethyl-benzamide or 2-[3-Bromo-1-(3-hydroxy-pyridin-2-y1)-1H-pyrazol-4-y1]-6-chloro-3,8-dimethyl-3H-quinazolin-4-ketone,3-bromo-1-(3-chlorop yridin-2-y1)-1H-pyrazole-5-carboxy1-ate, 3-bromo-1-(3-chloropyridin-2-y1)-1H-pyrazole-5-carbaldehyde, methyl 3-bromo-1-(3-chloropyridin-2-y1)-1H-pyrazole-5-carboxylate,3-brom o-N-(4-chloro-2-methylphenyl)-1-(3-chloropyridin-2-y1)-1H-pyrazole-5-carboxamide,3-bro mo-N-(2-carbamoyl-4-chloro-6-methylphenyl)-1-(3-chloropyridin-2-y1)-1H-pyrazole-5-carb oxamide. Moreover, we speculated degradation pathway for pure chlorantraniliprole un der simulated sunlight.This thesis was studied also about the effect of aquatic environmental coexisting substances on chlorantraniliprole photolysis under simulated sunlight irradiation. Results are as follows:The photolysis of chlorantraniliprole was in accord with the first order equation well. The rate constant has been gradually increasing and then decreased with pH value increased. Accordingly, the photolysis reaction of chlorantraniliprole was strongly inhibited in the acidic and basic conditions, and the photolysis reaction is easier to occur under neutral conditions. Environmental coexisting substances of NO3-, NO2-, NH4+ inhibits the photolysis of chlorantraniliprole. Form of inorganic nitrogen will transform with the pE value changes. Inhibition of different inorganic nitrogen forms coexisting in the aquatic environment on chlorantraniliprole had an obvious antagonistic action. The coexisting HCO3- can reduce the photolysis rate of chlorantraniliprole by reacting with hydroxyl radicals, and then inhibit the photolysis of chlorantraniliprole.Metal ions (Fe3+, Cu2+) inhibited the photodegradation of chlorantraniliprole due to light absorption competition with chlorantraniliprole. The photodegradation rate was found to decrease with increasing surfactant concentration. Acetone can accelerate the photolysis of chlorantraniliprole under the condition of low concentrations and inhibit under higher concentrations (1.0%, 2.0%). Humic acid inhibited the photodegradation of chlorantraniliprole. Formic acid and acetic acid restrained the photolysis of chlorantraniliprole due to the absorption wavelength overlaps the absorbance wavelength region of chlorantraniliprole and their strong acidity, which lead to light absorption competition with chlorantraniliprole. Propionic acid and butyric acid can promote reaction of the photodegradation of chlorantraniliprole by solubilizing effect.