阅读说明：本技术 一种二氯乙酰胺的合成方法 (Method for synthesizing dichloroacetamide ) 是由 伍雄飞 张复兴 许志峰 伍雄姿 刘梦琴 盛良兵 朱小明 刘明明 刘润 唐斌 罗园 于 2019-09-05 设计创作，主要内容包括：本发明涉及化学合成技术领域,具体为一种二氯乙酰胺的合成方法,主要采用以下步骤：向反应容器中加入二氯乙酸、二氯乙烷和固体酸,搅拌混合后对反应容器内反应液加热并通入氨气直至反应结束,反应液经处理后冷结晶获得二氯乙酰胺。本发明方法原料容易获取,步骤简单,易于操作,原料利用率高,并且不产生废弃物,反应过程中使用的有机溶剂可以循环利用。(The invention relates to the technical field of chemical synthesis, in particular to a method for synthesizing dichloroacetamide, which mainly comprises the following steps: adding dichloroacetic acid, dichloroethane and solid acid into a reaction vessel, stirring and mixing, heating reaction liquid in the reaction vessel, introducing ammonia gas until the reaction is finished, and carrying out cold crystallization on the reaction liquid after treatment to obtain dichloroacetamide. The method has the advantages of easily obtained raw materials, simple steps, easy operation, high utilization rate of the raw materials, no waste and cyclic utilization of the organic solvent used in the reaction process.)

1. A method for synthesizing dichloroacetamide comprises the following steps: firstly, adding dichloroacetic acid and solid acid into a reaction vessel, stirring and mixing, heating reaction liquid in the reaction vessel, introducing ammonia gas until the reaction is finished, and treating the reaction liquid and then carrying out cold crystallization to obtain dichloroacetamide.

2. The method for synthesizing dichloroacetamide according to claim 1, wherein: before the dichloroacetic acid and the solid acid are stirred and mixed, a low-boiling organic solvent is added in advance into the reaction vessel.

3. The process for the synthesis of dichloroacetamide according to claim 2, wherein: the low boiling point organic solvent is dichloroethane.

4. A process for the synthesis of dichloroacetamide according to any one of claims 1 to 3, wherein: the reaction vessel is a distillation still.

5. The method for synthesizing dichloroacetamide according to claim 1, wherein: the solid acid catalyst is boron-silicon series solid acid catalyst.

6. The process for the synthesis of dichloroacetamide according to claim 4, wherein: the molar mass ratio of the organic solvent to the dichloroacetic acid is 2: 1.

7. The method for synthesizing dichloroacetamide according to claim 6, wherein: the molar mass ratio of the dichloroacetic acid to the ammonia gas is 1: 1.01.

8. the method for synthesizing dichloroacetamide according to claim 7, wherein: the heating temperature of the reaction liquid is 60 degrees.

9. The method for synthesizing dichloroacetamide according to claim 8, wherein: under the condition of reduced pressure, steam generated after the reaction liquid is heated is condensed, then water is separated by using a water separator, and dichloroethane obtained after separation flows back to the reaction container to continue to serve as a solvent.

Technical Field

The invention relates to the technical field of chemical synthesis, in particular to a novel method for synthesizing dichloroacetamide.

Background

Dichloroacetamide is an essential intermediate for synthesizing dichloroacetonitrile, and the dichloroacetonitrile is an important intermediate of thiamphenicol and florfenicol.

Thiamphenicol is named as Thiamphenicol and thiamphenicol, is white crystalline powder, is odorless, is easy to dissolve in dimethylformamide, is slightly soluble in absolute ethyl alcohol and is slightly soluble in water, and the melting point is 163-167 ℃. Thiamphenicol is a congener of chloramphenicol, has similar antibacterial spectrum and antibacterial effect to chloramphenicol, has broad-spectrum antimicrobial effect, and comprises aerobic gram-negative bacteria, gram-positive bacteria, anaerobic bacteria, rickettsia, spirochaete and chlamydia. Thiamphenicol has bactericidal effects on the following bacteria: haemophilus influenzae, streptococcus pneumoniae, and neisseria meningitidis. Has bacteriostatic action only on the following bacteria: staphylococcus aureus, Streptococcus pyogenes, Streptococcus viridis, group B hemolyticus, Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Salmonella typhi, Salmonella paratyphi, Shigella, Bacteroides fragilis, etc. The following bacteria are generally resistant to chloramphenicol: pseudomonas aeruginosa, Acinetobacter, Enterobacter, Serratia marcescens, Indolapplication-positive Proteobacter, methicillin-resistant Staphylococcus, and enterococcus.

Thiamphenicol is a bacteriostatic agent, reversibly binds to 50S subunit of bacterial ribosome, prevents peptide chain growth (probably because of inhibiting transpeptidase action), and thus inhibits peptide chain formation, thereby preventing protein synthesis and showing complete cross drug resistance with chloramphenicol. Because thiamphenicol is not combined with glucuronic acid in the liver, the antibacterial activity in vivo is higher. The product has stronger immunosuppressive action, which is about 6 times stronger than chloramphenicol.

The traditional method for synthesizing dichloroacetamide is to react methyl dichloroacetate with liquid ammonia, then concentrate part of methanol and water, and then carry out freezing crystallization, and the method can generate a large amount of COD wastewater, and the residual methyl dichloroacetate can generate decomposition reaction in the concentration process to generate other impurities, so that the purity of dichloroacetamide after freezing crystallization is caused, and the yield of dichloroacetonitrile and the quality of dichloroacetonitrile can be reduced during the later-stage production of dichloroacetonitrile.

Disclosure of Invention

The invention aims to provide a novel method for synthesizing dichloroacetamide, which is simple and convenient, is easy to operate, has high utilization rate of raw materials, and does not generate waste.

A method for synthesizing dichloroacetamide mainly comprises the following steps: adding dichloroacetic acid and solid acid into a reaction vessel, stirring and mixing, heating reaction liquid in the reaction vessel, introducing ammonia gas until the reaction is finished, and treating the reaction liquid and then carrying out cold crystallization to obtain the dichloroacetamide.

Further, before the dichloroacetic acid and the solid acid are mixed with stirring, an organic solvent is further added to the reaction vessel.

Preferably, the organic solvent is a low boiling point organic solvent.

Further preferably, the organic solvent is dichloroethane.

Preferably, the reaction vessel is a distillation still.

Preferably, the solid acid catalyst is a boron-silicon series solid acid catalyst.

Preferably, the molar mass ratio of the organic solvent to the dichloroacetic acid is 2: 1.

Preferably, the molar mass ratio of the dichloroacetic acid to the ammonia gas is 1: 1.01.

preferably, the reaction solution is heated at a temperature of 60 ℃.

Preferably, under reduced pressure, steam generated by heating the reaction solution is condensed and then water is separated by using a water separator, and dichloroethane obtained after separation is refluxed into the reaction vessel.

In the above steps, the low boiling point organic solvent (such as dichloroethane) can be recycled, and the solvent acts as a water carrying agent, the water generated by the dehydration reaction of ammonia gas and dichloroacetic acid is continuously carried out from the reaction system under the condition that the dichloroethane is boiling, and the reaction product dichloroacetamide is supersaturated and exists in the reaction liquid, thereby creating conditions for the subsequent cooling crystallization to separate out dichloroacetamide crystals.

Advantageous effects

The traditional process uses methyl dichloroacetate to react with liquid ammonia to prepare dichloroacetamide, the product yield is low, the low-concentration methanol aqueous solution generated by the reaction can not be recycled, a large amount of waste water containing COD is generated, and the waste water can be discharged after post-treatment. The method has the advantages of easily obtained raw materials, simple steps, easy operation, high utilization rate of the raw materials, no waste and cyclic utilization of the organic solvent used in the reaction process.

Detailed Description

The process of the present invention is further illustrated below with reference to specific examples.