The ability of herbicides to be adsorbed by the soil and their tendency to be desorbed are some of the most important factors affecting soil and water contamination. Therefore, a sorption and desorption study were conducted to evaluate the adsorption‐desorption of cyhalofop‐butyl, in the sandy clay loam and at different depths using a batch equilibrium method. The adsorption of cyhalofop‐butyl was found positively related with the clay and organic carbon content. The kinetic profiles occurred in three steps. With an initial rapid adsorption in the early hours followed by slow adsorption and then it was constant during the rest of the range studied. Adsorption data conformed well to the Freundlich isotherm, whit increasing of adsorption with increasing of organic matter of the soil of different depth. The desorption process showed an important hysteresis phenomenon. The adsorption isotherm suggested a relatively higher affinity of cyhalofop‐butyl to the adsorption sites at low equilibrium concentrations. The low value of the soil organic carbon partition coefficient (Koc) of cyhalofop‐butyl in the sandy loam soil suggested its weaker adsorption in soil and thus increased its risk of mobility into water sources.

The thermal decomposition reaction of benzaldehyde diperoxide (DFT; 0.001 mol L-1) in nitromethane solution studied in the temperature range of 130.0-166.0 °C, follows a first-order kinetic law up to at least 60% DFT conversion. The organic products observed were benzaldheyde and benzoic acid. A stepwise mechanism of decomposition was proposed where the first step is the homolytic unimolecular rupture of the O-O bond. The activation enthalpy and activation entropy for DFT in nitromethane were calculated (DH# = 106.3 ± 1.0 kJ mol-1 and DS# = -58.6 ± 1.1 J mol-1K-1) and compared with those obtained in other solvents to evaluate the solvent effect.

The thermal decomposition of Cyclic Diperoxide of Benzaldehyde 3,6-diphenyl-1,2,4,5-tetroxane, (DFT) in chlorobenzene solution in the studied temperature range (130˚C-166˚C) satisfactorily satisfies a first order law up to 60% conversions of diperoxide. DFT would decompose through a mechanism in stages and initiated by the homolytic breakdown of one of the peroxidic bonds of the molecule, with the formation of the corresponding intermediate biradical. The concentration studied was very low, so that the effects of secondary reactions of decomposition induced by free radicals originated in the reaction medium can be considered minimal or negligible. The activation parameters for the unimolecular thermal decomposition reaction of the DFT are ΔH# = 30.52 ± 0.3 kcal•mol −1 and ΔS# = −6.38 ± 0.6 cal•mol −1 K −1. The support for a step-by-step mechanism instead of a process concerted is made by comparison with the theoretically calculated activation energy for the thermal decomposition of 1,2,4,5-tetroxane.

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