The Synthesis Of The Herbicides Of Diquat

Diquat is a non-selective contact herbicide and desiccant, developed by ICI Plant Protection Division (now Zeneca Agrochemicals).This paper mainly discusses the synthesis of diquat and its intermediates 2,2'-bipyridyls, thus obtaining its better technology in our experiments. The structures of diquat and its intermediates are characterized on IR,1H-NMR and MS.According to concerned papers ,we have chosen the way in which diquat dibromide is synthesized from 2,2'-bipyridyls and ethylene dibromide. This paper makes further research into its technology, thus obtaining better synthesizing conditions. The better reaction conditions for the way are as follows: The ratio of 2,2'-bipyridyls to ethylene dibromide(molar ratio)is 1:1.2; Reaction temperature is 211 ;Reaction time is 2 hours. Its yield is up to 73.5%.Our study gives the synthesis of 2,2'-bipyridyls by using pyridine in contact with hot Raney nickel catalyst. The way has advantages of low material cost and high yield. According to concerned papers, we have designed a special apparatus which is suitable for this reaction, and gives better results, therefore it has laid good foundations in industrial producetion. What is more, the way to preparation and regeneration of Raney nickel catalyst is studied tentatively.Our work to, develop diquat is mainly given in this paper. We hope that we can do our best in the development and production of diquat in our country.