Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: Juaqui on June 16, 2019, 12:01:21 PM
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Hello!
What could be the reasons for which DMF (as a solvent) cannot be avoided in a particular synthesis?
Thanks!
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Boiling point
Reactions
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solubility?
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Usually solubility. It can also be a reagent, like in Vilsmeier-Haack
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" Into a 3 L round bottomed flask compound (XIX)
from step-III (40 g) and dimethyl formamide (200 ml) were
charged. Potassium carbonate (96.9 g) and isobutyl bromide
(48.3 g) were added and the reaction mass was heated to
80-85° C. Reaction mass was maintained at the same tem
perature for five hours and brought to room temperature.
Water (2 L) was charged to reaction mass and stirred for one
hour. Reaction mass was filtered and washed with water
(2x500 ml). The wet compound was dissolved in Ethyl
acetate (1000 ml) and ethyl acetate layer was washed with
water (400 mlx3). Ethyl acetate layer was dried over sodium
sulphate and distilled off completely under vacuum. Metha
nol (240ml) was added to the residue and heated to 50–55°C.
and maintained at the same temperature for 15 minutes. Reac
tion mass was brought to room temperature and maintained
for one hour. The compound (XX) was filtered and dried at
50-60° C. "
Here, de reaction is a nucleophilic sustitution from a phenol to an Br-bencene (one step to the formation of febuxostat). DMF is hardazous, that is the reason that makes me wonder it...
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DMF is very low on my list of hazardous things. Just don't drink it.
But the fact that you are trying to synthesize this, but think DMF is hazardous does give me pause over whether you know what you're doing. I very much hope you are not planning to ingest this material.
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The phenol and bromide is much more toxic than DMF.
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DMF is very low on my list of hazardous things. Just don't drink it.
But the fact that you are trying to synthesize this, but think DMF is hazardous does give me pause over whether you know what you're doing. I very much hope you are not planning to ingest this material.
No, I'm trying to think about it because it is a possible question from my teachers to me.
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Oh. Well there is a well-known alternative to DMF that has similar properties. Do you know what it is?
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You can probably find the LD50 in rats for DMF in Merckś index
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Oh. Well there is a well-known alternative to DMF that has similar properties. Do you know what it is?
DMSO, maybe?
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Yep! DMSO is a common alternative that is friendlier to life. However DMSO is more reactive, so it can't be used in all situations.
I think in the case of the Williamson Ether synthesis you are describing it would work fine. Potassium carbonate has better solubility in DMF I think, so it is still a better choice all other things equal.
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I think a alkyl halide can react with DMSO if heated, this is a way of making aldehydes if I remember correctly, you can find this reaction in Marchś adv org. Chem.
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Oy! Kornblum oxidation, my apologies. Can't use DMSO in this reaction!
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Thanks for your answers!!