Preparation Of Dimethyl 2-fluoromalonate Using N,N-diethyl-2,3,3,3-tetrafluoropropionamide

Fluorochemicals have been widely used in many fields,such as coatings,lubricants,films,electrical materials,optical materials,refrigerants,medical equipment and pharmaceuticals.As important fluorinated compounds,2,3,3,3-tetrafluoropropionate methyl ester(MTFPN)and dimethyl 2-fluoromalonate(DFMN)have high application value in the fields of medicine,pesticides,etc.However,there are few reports on their synthetic research.The fluorinated antibiotic flufenicol is a fluorinated derivative of chloramphenicol and methanesulfomycin,which has an inhibitory effect on many bacteria.At present,the domestic production of florfenicol has exceeded 2000 tons/year,and each ton of production will produce about 1 ton of by-product N,N-diethyl-2,3,3,3-tetrafluoropropionamide((NDFPA),the mixed discharge of the by-products and sewage will have a serious impact on the environment.The cost of harmless treatment is high,and there are no reports of direct application of NDFPA.Therefore,it is imminent to seek a method for the resource utilization of NDFPA and conduct in-depth research on it.In this experiment,NDFPA was used as the raw material to generate 2,3,3,3-tetrafluoropropionic acid(TFPA)through acidic hydrolysis.MTFPN was prepared by esterification of TFPA with methanol.MTFPN was defluorinated,extracted,and acidified to obtain DFMN.The utilization of NDFPA,a by-product of florfenicol,was realized.The specific research contents and results are as follows:(1)TFPA was prepared by hydrolysis with NDFPA as raw material under acidic conditions,and the effects of hydrolysis temperature,sulfuric acid concentration,and NDFPA concentration on the effect of hydrolysis reaction were investigated.In the temperature range of 130?-150?,the conversion rate of NDFPA increases with increasing temperatureand finally remains stable.When the reaction temperature was 145?,the conversion rate of NDFPA reaches the maximum.The conversion rate of NDFPA increased with the increase of sulfuric acid concentration,and remained unchanged at last.When the sulfuric acid concentration was 5.91 mol/L,the conversion rate of NDFPA reached the maximum.With the increase of the initial concentration of NDFPA,the conversion rate of NDFPA increased first and then decreased.When the initial concentration of NDFPA was 3.41 mol/L,the conversion rate of NDFPA reached the maximum.Under the optimal conditions,the hydrolysis conversion rate of NDFPA reached 98.82%.(2)MTFPN was prepared by esterification of TFPA with methanol under acidic conditions,and the effects of esterification temperature,reaction time,and initial methanol concentration on the effect of the esterification reaction were investigated.In the temperature range of 70?-85?,the content of the reaction product MTFPN increased first and then decreased with the increase of temperature.When the temperature was 80?,the content of MTFPN was highest.The content of MTFPN first increased and then decreased with the increase of the reaction time.The optimal reaction time was 8 hours.The content of MTFPN first increased and then decreased with the increase of initial methanol concentration.When the initial methanol concentration was 4.64 mol/L,the content of MTFPN was the highest.Under the optimal conditions,the yield of MTFPN reached 98.42%.(3)The hydrolysis kinetics of NDFPA was studied.When the hydrolysis temperature is130?-150?,the initial concentration of sulfuric acid is 4.06 mol/L-6.69 mol/L,and the initial concentration of NDFPA is 3.1 mol/L-4.07 mol/L,the hydrolysis reaction of NDFPA accords with first-order kinetics,and its activation energy Ea is-100525 J/mol.The NDFPA hydrolysis model is:(?)(4)The defluorination reaction of MTFPN was studied,and the effects of defluorination temperature and reaction time on the defluorination effect were investigated.In the range of30?-60?,the content of the defluorinated product increases first and then decreases with increasing temperature.When the defluorination reaction temperature reaches 50?,the content of defluorinated products was the highest.The content of the defluorinated product increased first and then decreased with the increase of the reaction time.The optimal reaction time is 4 hours.(5)The extraction effect of four extractants on defluorinated products was studied,and the results showed that methyl tert-butyl ether had the best extraction effect.(6)GC-MS analysis was used to identify the intermediate products of the MTPPN defluorination reaction.Thirteen intermediate products(including the final product)were isolated and identified,and the mechanism of the MTFPN defluorination reaction was analyzed accordingly.