I have this compound in a DMF/ aq. NaOH mixture. Does anyone know a good way of separating my compound from this mixture? Someone recommended using brine. Has anyone ever tried this?
It is a common prolem on uage DMF. It's solution is dependet of solubility of the target compound in water and hexane. If it is possible to pure the mixture in water (large volume) and exract your target compound by hexane problems are finished. DMF does not go from water to hexane. If not, you have to exract by ether. Some DMF goes from water to ether so you will have a problem with separation (fracnional distillation of target compound and DMF). Using brine in this case increases the concentration target compound, but DMF too, in organic phase. If you compond not soluble in ether but soluble in water.... it's a pity. You have to evacuate all DMF with water (as a rule in such case target compound is not volatile, else you really loose), and cryslallize the residue. It you explain me namelly what compound you have got in DMF/aq NaOH solution I'm give more informative comments may be from my own experience
Yes, I have done it many many times. If the substance is hydrophobic – no problem – add water (10 times more on volume) and extract the substance with some hydrophobic solvent (I usually use DCM and EtOAc with no sufficient co-extraction of DMF).
If your substance has COOH, you also have to to balance pH down to achieve pH = 2-4 prior to extraction.
After you have collected your organic phase, I have found it beneficial to wash it with either 10% CuSO4, or 10% LiCl solution to remove residual DMF, followed by brine. I use this when extracting with Et2O or EtOAc.
This site is very useful by the way: http://chem.chem.rochester.edu/~nvd/pages/solvents.php?page=solvent_workup
If the compound of interest is not volatile, you can use high vacuum to remove DMF (remember to neutralize NaOH prior to concentration - if necessary for the target compound).
By the way, I used DMF for co-evaporation of DMSO-d6 of NMR-samples in high-vac (probably it also worked at 5mbar in the rotovap as well, i can't remember anymore). That means that you could also use DMSO for co-evaporation of DMF.
If the target compound is water soluble you can try to strongly dilute (10x) the reaction and freeze-dry. Again, make sure to neutralize before concentration.
Separate a compound from DMF , carry out vacuum distillation to remove DMF and then neutralize aq. NaOH with HCl to get your compd.
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