Sulaiman
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Can I expect good separation of haloform products?
I intend to try making chloroform by a few methods;
- calcium hypochlorite + acetone
- calcium hypochlorite + ethanol
- TCCA + acetone
- TCCA + ethanol
I'm expecting mainly
CH2Cl2 (b.p. 39.6),
CHCl3 (b.p. 61.2)
CCl4 (b.p. 76.7),
acetone (b.p. 56)* or ethanol (b.p. 78. 2)*
and H2O
* plus higher b.p. due to water?
I have a still that has 5 to 6 theoretical plates.
Can I expect a good separation of products?
If not then any suggestions?
[Edited on 13-7-2021 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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Amos
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I don't think you should expect anything other than chloroform, to be honest, if you use excess hypochlorite. The reaction exhaustively chlorinates
the terminal methyl group adjacent to a carbonyl carbon, and this then leaves as a trichloromethyl group to form chloroform. If it were to stop at
only two chlorinations, you'd end up with something like dichloroacetone or dichloroacetaldehyde, which none of us have ever seen evidence of.
Certainly not any carbon tetrachloride; it's not even a possible product.
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karlos³
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If you react acetone with aqueous calcium hypochlorite... expect a very vigorous and exothermic reaction.
It can be used though, with appropriate cooling, while dropping the acetone into, to distill the (acetone contaminated) chloroform right off of the
reaction mixture.
This way you still get a better yield than with the aqueous preparation where you separate it off in the end.
You need to wash and redistill though, but it works pretty well and much faster than the NaOCl methods, a few hours after you can already put the TCM
to good use.
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Oxy
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I also don't think you would get anything other than chloroform.
You will not get DCM as HCCl2- anion will not leave the adjacent carbonyl group easily.
CCl3- anion will do that easily as it is an excellent leaving group and very quickly will undergo a protonation by taking a hydrogen from nearby
water molecule. There is really low possibility that it would form CCl4 so I wouldn't expect any reasonable quantity.
Quote: Originally posted by Amos  | | If it were to stop at only two chlorinations, you'd end up with something like dichloroacetone or dichloroacetaldehyde, which none of us have ever
seen evidence of. |
Each halogenation of alpha-carbon makes it more acidic and more reactive. So it's not really possible to stop it after one or two substitutions in
basic conditions by using stoichiometric amount of chlorinating agent.
[Edited on 13-7-2021 by Oxy]
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Mateo_swe
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Is there no risk of phosgene if doing the acetone with aqueous calcium hypochlorite distillation preparation of chloroform?
I did a quick search on this method and found a rhodium preparation where they warn about phosgene.
A fumehood probably is good for this one, just chloroform vapours can make you pass out.
But i like the suggested preparation of chloroform, i might try it later if i need chloroform.
https://erowid.org/archive/rhodium/chemistry/chloroform.html
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Oxy
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No, there is no risk of phosgene formation during reaction. However, chloroform can itself decompose to phosgene so it should be stabilized before
putting on the shelf for storage.
Fume hood is always a good to have. When reaction is performed in closed system with fumes absorber on the end (or just extractor) it is quite safe.
The situation is totally different when using not air-tight system without any absorber or extraction. The fumes are toxic and should be avoided.
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Sulaiman
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This video shows chlorine bubbling through chloroform producing carbon tetrachloride.
https://www.youtube.com/watch?v=YdSoTBHEU0A
Should I not expect this as a side reaction ?
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Oxy
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I don't think so.
If you bubble chlorine gas through chloroform then the reaction conditions are definitely different than when you use water solutions of hypochlorite
and acetone with continuos distillation.
Chlorination of chloroform you posted looks like a radical reaction which obviously will not happen when performing haloform.
When you perform the reaction in water remember that the concentration of water (which is about 55.56 moles/dm3) is a tough competitor. It is much
more likely for a compound to react with water than other things (if is water -reactive).
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SWIM
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I'm skeptical about that reaction in the link.
I don't think that works without UV
Also, Len1 and Magpie both used UVC to do this reaction, and I'd be surprised if both of them went to the trouble of making UVC sources for this
reaction if it was unnecessary.
And even more surprised that nobody pointed that out when Magpie posted that thread.
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Sulaiman
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OK... I think I get it... thanks.
I've got all required reactants, just cleaning and drying everything and looking for an affordable pressure-equalising addition funnel.
(I have some at home in UK, new ones seem to have significantly increased in price,
as has most glassware - and most other items.)
(The cost of food has risen significantly)
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Oxy
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| Quote: Originally posted by SWIM | I'm skeptical about that reaction in the link.
I don't think that works without UV
Also, Len1 and Magpie both used UVC to do this reaction, and I'd be surprised if both of them went to the trouble of making UVC sources for this
reaction if it was unnecessary
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Strong light is enough to initiate it. Not enough to keep it going at high rate but for simple demonstration can be just ok. For synthetic purposes
the more energy, the better.
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