My compound is soluble in THF ,DCM and Toluene .I am doing small scale crystallization in 5 ml vial taking 10 -20 mg of solid compound in each vial. I have already tried THF, THF/Pentane, DCM, DCM/Pentane, Toluene, Toluene/ Pentane combinations. In case of Toluene, I am getting ppt. In case of THF and DCM, even after 2nd and 3rd pentane layering I am not getting anything, not even ppt. Now what could be the solution ?What are the things that I should try ? I will highly value each of your suggestions.
Hello.
I don't know what is your solute, but there are some rules for solventing -out crystallization sometimes named two solvents crystallization:
1)The first solvent should dissolve your product very well .
2) The second solvent should NOT dissolve the product AND IT SHOULD BE COMPLETELY MISCIBLE IN THE FIRST SOLVENT.
Have you checked:
1) is the second solvent a non solvent for your product?
Are the pair of solvents miscible?
If you have already tried several solvent combinations for your small-scale crystallization and have not been successful, there are a few additional things you can try.
Firstly, you can try adjusting the temperature during the crystallization process. Lowering the temperature can sometimes help induce crystallization. You can also try adding a small amount of seed crystal to the solution to encourage crystallization.
Secondly, you can try a two-solvent crystallization method. This involves dissolving the compound in a solvent that is a good solvent at a high temperature but a poor solvent at a lower temperature (such as THF) and then adding a second solvent that is a poor solvent for the compound at all temperatures (such as hexane or heptane). By slowly cooling the solution, the good solvent will gradually become less effective at dissolving the compound, which will start to precipitate out of the solution due to the presence of the poor solvent. You can then filter the crystals and wash them with the poor solvent to remove any remaining impurities.
Finally, you can try a different technique such as slow evaporation or anti-solvent precipitation. Slow evaporation involves allowing the solvent to slowly evaporate over time, which can sometimes induce crystallization. Anti-solvent precipitation involves adding a poor solvent to the solution to induce precipitation of the compound.
It is important to note that the best method for crystallization will depend on the specific compound and its properties, so it may require some experimentation to find the most effective approach. Additionally, it may be helpful to consult with colleagues or experts in the field for additional guidance and suggestions.
Thank you Raghd Muhi Al-Deen Jassim and SILAS DERENZO for your kind responses. Raghd Muhi Al-Deen Jassim As you mentioned that it might require some experiment, but in my case I think I did a lot of experiments. Low temp, RT, One solvent, two-solvent . May be I need to try more, but I just wanted to ask if there is any simple and straightforward point that I am constantly missing. Thank you again.
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