Method for electrochemically preparing 3-methyl-3-butenoic acid in SC-CO2 system

Abstract

The invention discloses a method for electrochemically preparing 3-methyl-3-butenoic acid in an SC-CO2 system. The method comprises the following steps that carbon dioxide fluid and 3-chlorine-2-methyl-1-propylene are used as raw materials, ionic liquid-butyl-3-methyl imidazolium tetrafluoroborate is used as electrolyte, the raw materials and the electrolyte are subjected to constant-current electrolysis in an electrolytic tank after being mixed, the mixed product after electrolyzing is decompressed to recover carbon dioxide, and then is pressed into a micro-pore filter to be filtered by using residual pressure, filtrate is reused as the raw material, filter residue is acidified by hydrochloric acid to generate acidification liquid to be heated and evaporated, evaporated gas is cooled and crystallized to obtain the 3-methyl-3-butenoic acid, magnesium chloride is recovered from evaporation residual liquid by using an MVR technology through the residual heat of the evaporation residual liquid. According to the method, the electrochemical synthesis technology is adopted, the operation is convenient, the cost is low, and the yield is high; and only the hydrochloric acid is needed to be added in the electrolysate for acidification to generate the product, no solvent and extraction agent are added; and energy conservation and environmental protection are achieved, the carbon dioxide gas which can cause the greenhouse effect cam be effectively utilized, so that the method has great significance on environmental protection.

Description

technical field [0001] The invention relates to the technical field of organic chemical synthesis, in particular to a SC-CO 2 A method for electrochemically preparing 3-methyl-3-butenoic acid in a system. Background technique [0002] 3-methyl-3-butenoic acid is an important chemical raw material and organic synthesis intermediate, the English name is 3-methyl-3-butenoic acid, and the molecular formula is C 5 h 8 0 2 , it is a colorless flaky crystal with a melting point of 21.8°C and a spicy taste, soluble in alcohol and ether, easily soluble in hot water, volatile with water vapor, and hardly soluble in cold water. It is widely used in various aspects such as synthetic drugs, resins, fungicides, surface coatings and plasticizers. [0003] There are the following methods for the preparation of 3-methyl-3-butenoic acid abroad: [0004] 1. Amos B.Smith et al. used 3-methyl-3-butenol as raw material in J.Am. Chem. Soc., 1981, 103: 1996-2008, adding Jones reagent Cr 2 o ...

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Problems solved by technology

[0004] 1. Amos B.Smith et al. used 3-methyl-3-butenol as raw material in J.Am. Chem. Soc., 1981, 103: 1996-2008, adding Jones reagent Cr 2 o 3 , oxidation gives 3-methyl-3-butenoic acid, but due to Cr 2 o 3 The use of the three wastes is not easy to deal with, causing serious environmental pollution and does not meet the requirements of green chemistry

[0005] 2. Scholte, Andrew A, etc. carried out a multi-step reaction in Organic & Biomolecular Chemistry, 2006, 4:730-742. First, at room temperature, THF was used as a solvent and 3-chloro-2-methylpropene was used as a raw material. Add Mg powder to prepare the Grignard reagent; secondly, at -78°C, in the synthesized Grignard reagent, under the condition of iodine simple substance as the catalyst, pass CO 2 Synthesis of 3-methyl-3-butenoic acid with a yield of 39%. The Grignard reagent preparation conditions are harsh and the reaction reagents are used more and the reaction steps are cumbersome, and the conditions at -78°C are harsh and difficult to operate

[0006] 3. In J. Org. Chem., 2000, 65: 7475-7478, Mohamed Abarbri synthesized 3-methyl-3-butenoic acid by reacting the corresponding alkenoic acid or alkynoic acid halide with Grignard reagent, but All obtain the mixture of 3-methyl-2-butenoic acid and 3-methyl-3-butenoic acid, which is not easy to separate, and the yield is less than 60%, and catalyst and Grignard reagent are used in the reaction process

[0007] 4. In Org. Chem., 2000, 65:7475-7478, Mohamed Abarbri also reacted epoxy enone with Grignard reagent to obtain 3-methyl-3-butenoic acid. The preparation conditions of Grignard reagent were also harsh and The disadvantage of its own instability

[0008] 5. Aveya. Morto et al. first formatted pentane at -10°C to -15°C on Cambridge Mass, 1945, 67: 2224-2228, and then generated formatted reagents reacted with butene, and introduced CO 2 Obtain 3-methyl-3-butenoic acid, but the conditions for the preparation of Grignard reagent by this reaction are relatively harsh, difficult to operate, and the generated intermediate is unstable and easy to deteriorate

This preparation method has the following disadvantages: the electrolyte uses a very volatile acetonitrile solvent, and when the subsequent electrolyte is acidified, the acetonitrile solvent will be recovered by distillation; the acid-treated electrolyte will also be extracted three times with ether, and the ether in the extract will be combined. layer, and then wash the combined extract ether layer with deionized water once, remove the moisture in the extract with anhydrous magnesium sulfate, filter to remove anhydrous magnesium sulfate, and rotate the filtrate under reduced pressure at a certain temperature by a rotary evaporator to remove The product can only be obtained after the ether is removed by analysis. The post-treatment purification process is too complicated and the production cost is high.

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