Parakeet
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DCM vs. Chloroform for Extractions
I am planning to buy chloroform in the near future for extractions and organic synthesis, but I am not sure if I should also buy DCM. I can buy both
of them for almost the same price.
Is there any cases that chloroform cannot be used but DCM can?
Do you use both?
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crow6283
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I use both also use DCE sometimes DCM is nice and can be removed more quickly but also more prone to emulsions.
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Mush
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Chloroform is suspected to be a human carcinogen and is known to be carcinogenic to animals.
"There are two main reasons for choosing DCM (dichloromethane, CH2Cl2) vs. chloroform (trichloromethane, CHCl3) as the extraction solvent.
Boiling point of CH2Cl2 (~ 42 deg. C) is much lower than that of Chloroform (~ 62 deg. C). Removal of solvent extract is made much easier for
CH2Cl2 as compared to CHCl3.
HS&E (health, safety and environment) impact of CHCl3 is much higher than that of CH2Cl2. Chloroform is more toxic and has a much greater
environmental impact on destruction of the ozone layer. If you have to choose between these two solvents, CH2Cl2 is always the safer choice.
reference: http://file:///C:/Users/Watchout1/Downloads/30203-Article%20Text-56638-3-10-20190824.pdf"
https://www.quora.com/What-is-the-difference-between-chlorof...
[Edited on 4-3-2023 by Mush]
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SplendidAcylation
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DCM is approximately twice as soluble as chloroform in water, at room temperature, so you lose a bit more when you are washing aqueous stuff with it.
DCM is a lot safer than chloroform, it doesn't form phosgene so readily... But DCM is also toxic and since it is more volatile it is more liable to be
inhaled without proper ventilation, I suppose.
Don't treat it like a relatively harmless solvent such as ether, DCM is almost odourless too so it is easy to overlook high concentrations in the air.
As for specific differences, chloroform is a good solvent for hexamine, whereas DCM isn't, so you need chloroform for the Delepine reaction! 
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Texium
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Putting aside the health hazards for now, I think chloroform is generally a better solvent to work with than DCM, as far as ease of extractions (less
water soluble, higher density, cleaner layer separation) and just usually dissolving organic substances faster and in greater concentration than DCM
will. Most of the time, I prefer chloroform for extractions, although I generally avoid halogentated solvents entirely and use ethyl acetate whenever
possible.
One drawback of chloroform though that hasn't been pointed out yet is that it is significantly more acidic than DCM or other aprotic solvents. In the
presence of strong bases, it can be deprotonated to form trichloromethyl anion, which can lead to unwanted side reactions (see chlorobutanol synthesis
for an intentional use of this property). This makes chloroform unsuitable for extracting compounds from a strongly basic aqueous solution, or for
using as a solvent for a reaction involving a strong base. Additionally, there can be HCl present in chloroform due to decomposition, which I have
witnessed ruin acid-sensitive reactions. If necessary, it can be neutralized with potassium carbonate or calcium carbonate prior to use.
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Texium
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Thread Moved
4-3-2023 at 14:52 |
Parakeet
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Thank you for your advice.
I think I will first get some chloroform and see how it works. Most of the alkaloids I want to extract seems to be okay. If it dosn't go well, I'll
consider buying DCM.
The toxicity is a bit of concern, so I will be careful not to breath in too much.
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Fantasma4500
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DCM for sure, chloroform you can make yourself- DCM, well good luck.
not to mention the vast solubility difference. DCM however can cause a limb to die if you inject yourself with it, cases are known where just very
small amounts, residue of DCM causes necrosis of - was it, a whole hand?
DCM can also be used to extract concentrated nitric acid and i believe also elemental bromine
once again- chloroform can be made
DCM has 1.5 xlogp3 polarity
chloroform is 2.3
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