How to prevent the solute from precipitating during the removal of the solvent by distillation?
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I’m conducting an experiment, and the intermediate product is a compound that tends to polymerize, especially at high temperatures with little solvent present. During the preparation process, this compound exists in an aqueous solution, but the final product is used in an alcohol-based solvent system. The method I used was to add an alcohol and then remove the water through vacuum distillation. However, as the amount of solvent decreases during the distillation process, the solute adhering to the walls of the flask aggregates and precipitates rapidly due to the reduced solvent level. Moreover, since distillation is carried out in an oil bath, the residual material on the flask walls experiences rapid heat transfer, resulting in relatively high temperatures that further accelerate the process of aggregation and precipitation. Reflection: Since at the end of the experiment, solute precipitation mainly occurred only on the wall of the flask (above the liquid surface), with very little precipitation below the liquid surface (possibly due to the boiling process carrying precipitates from the flask wall into that area), it is initially believed that product polymerization was caused by the reasons mentioned above. I hope those who have encountered this problem can suggest a solution to help resolve it. I came up with a method of my own: during the distillation process, add the components of the solution before distillation (the compound + water + alcohol) drop by drop, so as to ensure that water is distilled off while the liquid level remains constant, and the entire system gradually approaches the alcohol-based system I want. But regarding the specific procedures, since it involves vacuum distillation, I would appreciate it if friends could give some advice on how to carry out these operations! Friends, please share your thoughts! Moreover, this method can only approach the alcohol-soluble system I want; it is unable to achieve the system I require in the end. So if there are other ways to achieve the goal, those can also be tried! Finally, let me say thank you first
1. Can the temperature be controlled properly, so that it’s not too high (to prevent the solution from splashing too high and causing precipitation)?； 2. Can a simple device be added to continuously supply the alcohol solvent, in order to maintain a stable temperature (preventing excessive boiling) while also keeping the liquid level constant? ；
It is recommended to use an appropriate extractant to extract the solute； Or direct two-phase reaction extraction. Many alcohols are insoluble in water.
I think you’re beating around the bush. Do you really mean to remove the water from your intermediate and turn it into an alcohol solution? With vacuum distillation at 50 mmHg pressure, water can be completely removed; there’s no need to turn on the heating function of the magnetic stirrer. . . . This post was last edited by vivasun851228 on 2009-4-14 13:52.]
Just find an alcohol solution and perform multiple extractions. Isn’t that fine? Also, leaving aside the operational issues for now. . Tell me what you do; just respond to any questions related to organic synthesis. . . Let’s discuss it. . . . . If it is a polymer. 、。 There’s nothing that can be done…… What is the substrate? What are the reactants? . . . . What type of reaction? . . Let’s start by discussing the mechanism. This post was last edited by vivasun851228 on 2009-4-14 13:54.]
It seems you are using simple distillation; you might try rotary distillation. Additionally, you can determine the polymerization temperature of this compound to avoid blind pressure reduction and heating.
The friend upstairs is right; it’s actually a process of solvent substitution, turning an aqueous solution into an alcoholic solution. Extraction certainly won’t work; the alcohol I use is ethylene glycol, which is miscible with water. At first, I thought that simply distilling off the water component using vacuum distillation would be sufficient. But the problem is that as the liquid level drops during distillation, the solutes remaining on the walls of the flask will precipitate as the amount of solvent decreases; they stick to the walls of the flask and then aggregate further, no longer being what I wanted! Also, due to the bubbling that occurs during vacuum distillation, the portion that splashes onto the walls of the flask will eventually precipitate as well. The suggestions for the second floor are good; I’ll give them a try first!
I achieved my goal by adding the solution of the same composition while distilling, and thanks to everyone for their suggestions!