Green Synthesis Of Pendimethalin

In the 21'st century the conflicts between population increase and foodsupplies are becoming serious. Moreover, plowland decreasing caused by cityexpanding and circumstance worsen made the situation being more serious. Toincrease the working efficiency and quantity of food supplies, large scaleemploying of pesticide in modern agriculture produce are necessarily. Sinceherbicide play a key role in pesticide, development and research of good herbicidearising attentions of pesticide company and research institutes. Pendimethalin, which was firstly developed by American CyanamiolCompany(now belonging to BASF), was a kind of aniline herbicide. Being themost widely used herbicide, Pendimethalin owns many good properties such ashigh efficiency, long period of validity, versatile appling methods, low toxicity tohuman and livestock, friendly to circumstance, etc. Consequently it was used formany crops and vegetables include cotton, potato and corns.Traditional synthesis route of Pendimethalin which used 3,4-dimethylanilineas starting material has many shortages includes low purity of product, high acidcontent of wasted water, large consumption of hydrochloric acid, high failurepercent for equipment and severe operating conditions. In this thesis, a greensynthesis route was determined.The green route is described as below: 4-nitrodimethylbenzene was used asstarting materials, which was converted to N-(1-ethylpropyl)-3,4-dimethylanilinevia hydrogen adding reaction, after another nitrating reaction pendimethalin wasobtained. This synthesis route has several advantage compared to the route using3,4-dimethylaniline: Firstly, the steps of reaction was compressed from three stepreactions to one step reaction ,the cost of raw materials was reduced. Nitrogencompounds are low toxic to catalyst then its service time was extended;Secondly,the feed resolving is easily because to 4-nitro-1,2-dimethylbenzene is diffluent in3-pentanone compared to 3,4-dimethylaniline which need an additional solvingstill;The solvent for nitrating was changed from trichloromethane todichloromthane then removal of solvent could be completed at normal pressure.The consumption of hydrochloric acid was reduced to 1/10 of those in the oldroute. The failure percent of equipment was depressed while the operatingconditions were improved. Post-treat was easily since all wash was performed inone still, however the old route need another two wash still one solvent-removalstill. The content of waste acid in waste water was decreased form 50% to 1%.Lastly, the purity of product could reach above 96% at same conversion rate.Additionally, the product could be washed after dissolving in xylol to obtainedlatex, consequently the cost was reduced compared to the old route sincepetroleum ether was saved.Generally, the route discovered in this thesis could made resources beingutilized enough and made waste product being decreased, while contribute toagriculture production and environment production.