Synthesis Of Several Herbicides

In recent years, the development of chemical herbicide was extremely prompt, that there were more than200kinds of chemical herbicide in the market. The history of our chemical herbicide development has been over half a century, unfortunately, with a low speed. That the rate of chemical herbicide usage in developed country was over70%while the domestic one still being very poor, brought a tremendous meaning to the researches on the synthesis technology of well-employed chemical herbicide domestically.Bentazon,2,4-D, benthiocard and cyhalofop-butyl were broad-spectrumed chemical herbicides with great domestic consumptions. These years, the manufacture of these herbicides were realized cosmically, but the large-scale employment of chemical herbicide in agricultural produce was baffled by their shortages of low-rate production, bad selectivity, lack-developed technology, serious pollution and so on. Thus, through innovation or improvement of operation conditions, developing synthesis routes which are both easy and environmental-friendly, and applying these new synthesis methods to industry manufacture will bring great economic profit and promote the usage of chemical herbicide in agriculture.A serial of synthesis methods were established focused on bentazon,2,4-D, benthiocard and cyhalofop-butyl. Bentazon was prepared by the popular method of isatin anhydride, via investigation on the influence of solvent, temperature, concentration and catalyst, the yield of ammonolysis reaction reached to94%, the total yield of bentazon was over81%;2,4-D was prepared by later-chloridized method, while the influences of chlorination temperature, chlorine dosage and catalyst were observed. The target product yield was95%proceeding reported level by the chlorination method of adding a small quantity of catalyst into dichloromethane and inputting chlorine gas directly. On the base of synthesis method of benthiocard reported lately, the influences of different solvent and catalyst were studied further. The preparation method of benthiocard was determined as inputting carbon monoxide directly into the mixed solvent of diethylamine and sulfur, with the ending point of reaction detected, adding corresponding amount of p-chlorobenzylchloride into the system, the yield of benthiocard reached100%; tetrabutylammonium hydrogen sulfate was applied as catalyst based on patent, by a one-stepped method, the total yield of cyhalofop-butyl was94%with a optic purity of98%.