ADAMA Makhteshim Ltd.

The kinetics and thermodn. of a Wittig-Horner reaction was investigated, together with side reactions such as the hydrolysis of benzyl phosphonate.It was found that the water content in the reaction mass has a crucial effect on the rates both of the unwanted hydrolysis of the phosphonate and of the main reaction.The reaction was found to be fourth-order.That means that the reaction is very fast at the start but tails off towards the end.On the basis of the kinetic and thermodn. parameters, a simulation of the whole process was made, including the expected concentrations of the product under the required conditions (temperature, reactor characteristics, etc.).The exptl. values of the concentrations were obtained from spectra collected via a rapid reaction mode in the ReactIR (a spectrum was collected every ∼3 s).Exact agreement between exptl. and theor. values confirms the correctness of the math. model and enables right planning of the industrial process.

Phase solubility analysis (PSA) was used to establish purities of 3 organochlorine fungicides—chlorothalonil, captan, and folpet. Each ground sample was added to an equal amount of solvent. All vials were mixed at identical constant temperature, equal aliquots of liquid phase were removed and weighed, and concentration of dissolved material was determined by weighing the residue after evaporation to a constant weight. Solvent systems were chosen such that solubility of the fungicides was minimal. Data were analyzed by the leastsquares method with a resulting correlation coefficient of better than 0.94. Spiking experiments were also performed. Analysis of chlorothalonil by differential scanning colorimetry and of captan and folpet by liquid chromatography was in accord with PSA results.

A liquid chromatographic (LC) method for the determination of ditalimfos, 0,0-diethyI phthalimidophosphonothioate, is described. Bonded phase high precision LC using a mixture of n-hexane and chloroform as eluant afforded a capacity factor (k') of 2.3 for the analyte. Ditalimfos could be detected at 0.5 ppm (signal to noise ratio > 3) using ultraviolet detection at 254 nm. The detector afforded a linear response from 0.2 to 10.9 mg/mL when 10 μL of solution was injected and the coefficient of variation was ±0.5%. Structurally related fungicides and several common insecticides were successfully separated from the analyte under the chromatographic conditions of analysis.