Method for preparing p-fluoro anisole

Abstract

The invention discloses a method for preparing p-fluoro anisole, which comprises the following steps of: adding bromofluorobenzene, a solvent DMF (Dimethyl Formamide), liquid sodium methoxide and a catalyst into a reactor sequentially; heating the reaction system with stirring to perform the reaction of generating the p-fluoro anisole; performing the reaction for 10 to 15 hours continuously in the heating process; after completing the reaction, filtering a reaction mixture material to remove the catalyst; adding a liquid mixture material obtained after filtering into a distillation flask witha Nernst water separator, and then filling distilled water or water vapor into the distillation flask; heating the distillation flask to firstly evaporate out methanol, continuously heating the distillation flask until p-fluoro anisole and water are evaporated out in an azeotropic mode; with the continuous evaporation of p-fluoro anisole, collecting an organic phase at the lower layer of the Nernst water separator and ensuring a water phase to flow back into the distillation flask through the water separator; and feeding the organic phase collected from the Nernst water separator into a rectification device to be rectified so as to obtain a p-fluoro anisole finished product.

Description

technical field [0001] The invention relates to a preparation method of p-fluoroanisole, in particular to a preparation method for producing high-purity p-fluoroanisole. Background technique [0002] p-Fluoroanisole (p-Fluoroanisole, CAS: 459-60-9) is an important intermediate of medicine, pesticide and liquid crystal material, widely used; p-Fluoroanisole is a colorless to slightly yellow liquid, The boiling point is 157°C and the specific gravity is 1.114. [0003] At present, the production process of p-fluoroanisole has the following route: first react fluorobenzene with concentrated nitric acid to generate p-fluoronitrobenzene and m-fluoronitrobenzene, and then separate p-fluoronitrobenzene and m-fluoronitrobenzene to remove m-fluoronitrobenzene, reducing the obtained p-fluoronitrobenzene to obtain p-aminofluorobenzene, then adding sodium nitrite and p-aminofluorobenzene for diazotization reaction to form a diazonium compound, and then hydrolyzing the diazonium compoun...

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Problems solved by technology

[0006] But when we tested according to the method disclosed in the above-mentioned patent documents, we found that sodium hydroxide (or potassium hydroxide), methyl alcohol, and p-bromofluorobenzene could not carry out the condensation reaction under the catalysis of copper oxide (or cuprous oxide) as reactants, and also That is, p-fluoroanisole cannot be obtained according to the technical scheme, and p-bromofluorobenzene is replaced by p-chlorofluorobenzene for testing, but the reaction still cannot be carried out

[0007] In addition, even if the reaction can be carried out according to the above-mentioned scheme, from the examples of the description of the document, it is also proposed that the conversion rate of the reactant into p-fluoroanisole is 90% to 99%, if the conversion rate of p-fluoroanisole Below 95%, then after the reaction finishes, unreacted p-bromofluorobenzene also needs to be separated from product p-fluoroanisole, and the solubility properties of p-fluoroanisole and p-bromofluorobenzene are very close, and to The boiling point of fluoroanisole is 157°C, the boiling point of p-bromofluorobenzene is 153°C, and the volatility is also very close. According to the conventional intermittent rectification separation method, a rectification column with 40 theoretical plates is used, and then 10 : 1 reflux ratio, if the purity of the collected p-fluoroanisole is to reach 99.5%, then the yield of p-fluoroanisole after rectification can only reach about 20%, so it is not easy and not easy according to the conventional separation method Economical; if N,N-dimethylformamide is selected as the solvent during the reaction, its solubility properties are close to those of the above-mentioned p-fluoroanisole and p-bromofluorobenzene, and the boiling point of N,N-dimethylformamide is 152.8°C , the separation of the three substances is more difficult

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