Optimization Of The Synthesis Process Of 2,4-dichlorophenoxyacetic Acid And Its Esters

2,4-dichlorobenzene oxygen ethanoic acid(2,4-D for short)and its ester are kinds of phenoxy acetic acid herbicide which is widely used in preventing and killing off broadleaf weeds.Otherwise,they are used as plant growth regulator to stimulate crop growth and precocity.In this paper,the green synthesis process of 2,4-D and its ester were researched in detail,in order to overcome the serious environmental pollution because the industrial wastewater with the phenol of high content is difficult to deal with.First,the synthetic route of 2,4-D was determined.(2,4-Dichlorophenyloxyacetic)acid was prepared from the high purity of 2,4-dichlorophenol and methyl chloroacetate by one-pot reaction of eondensation,hydrolysis and acidification.Ultimately,the optimum condition was determined by single factor and orthogonal experiments in an overall yield of 96.8%and purity of 98.8%.The percent conversion of 2,4-dichlorophenol was 99.9%and the phenol content in the wastewater was below 50 ppm.The technology has several advantages,which are simple operation,recycled solvent,low content of free phenol in wastewater and green environmental protection.Second,the synthetic route of 2,4-D esters were determined.2,4-D esters were prepared from the high purity of 2,4-dichlorophenol and corresponding chloroacetates by condensation.Ultimately,the optimum condition was determined by single factor and orthogonal experiments in an overall yield of 95%and purity of 95%.The percent conversion of 2,4-dichlorophenol was 99.9%and the free phenol existed in product was below 0.1%.The technology has the advantages of simple operation,recycled solvent,green environmental protection,no wastewater,high yield and purity product.In addition,a quantitative analysis method for determination of isooctyl 2,4-D and related substances were established by HPLC,and the precision and the accuracy of this analysis method were good.The products of 2,4-D methyl ester,2,4-D butyl ester,isobutyl 2,4-D ester and isooctyl 2,4-D ester were analysed by GC-MS,and the impurity potential sources were determined which laid a foundation for process improvement.