Oncorhynchus
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Successful Chloroform Synthesis
Although this forum is no stranger to the preparation of CHCl3 from acetone and bleach, I figured I'd share my recent success with a
small-ish scale synthesis and contribute to the archives.
As it was the first experiment in my new abode, I figured I'd start with something simple. Using pool chlorinator (bottle said 7-12% NaClO, I assumed
7) and Klean Strip acetone straight from the can, I managed a higher than expected 79% yield of crude product that I will eventually purify through
distillation.
Briefly, my procedure went as follows:
Added 800 mL of the pool chlorinator to a 1 L glass media bottle and chilled to approximately -13 C (it actually got fairly slushy). Once chilled, a
stir bar was added and the bottle was placed in a salt/ice bath that remained between -2 and 2 C throughout the reaction. After a few minutes of
magnetic stirring, 9 mL of cold acetone was added, the bottle was lightly capped, and the reaction was allowed to proceed for about 10 minutes. Once
the temperature stabilized at around 1 C, the second 9 mL portion of acetone was added and the reaction was allowed to proceed until the green color
had dissipated. After the temperature peaked at 16 C and began to drop, the reaction was removed from stirring and allowed to settle.
Once settled, the aqueous layer was transferred to a waste container and the remaining water and CHCl3 were transferred to a separatory
funnel. The CHCl3 layer was drained directly into another separatory funnel and washed once with saturated NaHCO3 solution
(could've used NaCl, but meh). The product was transferred to a preweighed bottle for storage and the crude yield was found to be 23.76 g (79% based
on acetone). To slow decomposition, a few drops of >95% EtOH were added and the bottle was wrapped in aluminum foil.
Anyone have any thoughts on what I did well/poorly/etc based on the brief writeup?
[Edited on 27-9-2022 by Oncorhynchus]
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j_sum1
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Seems like you did well here. You kept the temperature nice and low. And you separated your product quickly so as to not get degradation with NaOH
present.
It is remarkable how accessible this particular reaction is. And always satisfying to accomplish.
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Fery
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Well done! Your yield is very nice!
I would try to recover some extra small quantity of chloroform from the water phase, but maybe it wouldn't be worth it...
Maybe by distilling small amount of water+chloroform mixture from the water phase.
Maybe by salting out the water phase.
Solubility of chloroform in pure water is: 10.62 g/L (0 °C) 8.09 g/L (20 °C).
But you had some salts present in water phase so you certainly had much less of chloroform in water phase than the solubility in pure water.
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Mateo_swe
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Can this simple preparation be done with Calcium hypochlorite and acetone also?
I have a box of solid Calcium hypochlorite for use in pools.
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j_sum1
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Quote: Originally posted by Mateo_swe  | Can this simple preparation be done with Calcium hypochlorite and acetone also?
I have a box of solid Calcium hypochlorite for use in pools.
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Yes. But separation is more difficult. IIRC, it is possible to get even higher yield with Ca(OCl)2. But I remember that I was not particularly
successful last time I tried and I went back to supermarket bleach.
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Mateo_swe
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Maybe mix calcium hypochlorite and water, chill, add acetone and when reaction seem complete as temp goes down, then distill out the chloroform from
the reaction mixture.
Could this work and is there any danger to try this idea?
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Fery
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Mateo_swe - interesting idea. Ca hypochlorite is quite cheap and widely available. Easier to transport as it is solid while Na hypochlorite is only as
a solution in water. Some sellers in my country do not send solution of Na hypochlorite by curriers (you have to visit them personally) but send solid
Ca hypochlorite without any problem. Maybe Ca hypochlorite is even more stable than Na hypochlorite which must be stored in cold (so older solutions
have lower concentrations).
I would neutralize the final mixture before distillation as the Ca hypochlorite contains excess of hydroxide - with acetic acid? citric acid? or cheap
HCl under control of indicator or pH meter? Also insoluble calcium salts tend to fall to the bottom so maybe magnetically stirring the content in a
distillation flask?
[Edited on 13-10-2022 by Fery]
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Keras
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I've tried that. This is a mess. Calcium acetate is little to not soluble in water, adsorbs about all the chloroform. The work-up is impossible to
carry out.
Best way if you want to increase the yield is to make your own sodium hypochlorite, by bubbling Cl₂ into a NaOH solution. But then again, be careful
because the haloform reaction is highly exothermic, and acetone should be dripped into the resulting concentrated NaClO solution.
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Mateo_swe
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Maybe its better to use Sodium hypochlorite (bleach in the stores) then.
Sad that Ca hypochlorite cant be used easily as its so avaliable in the form of pool chlorinating powder.
I guess one could make the Sodium hypochlorite as Keras suggestion.
If larger amounts of chloroform is needed this might be the best economical option.
A simple sodium chloride solution with 2 electrodes from a power supply makes chlorine gas at one of the electrodes if i remember correctly.
But maybe there is better ways of generating chlorine gas.
[Edited on 2022-10-14 by Mateo_swe]
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j_sum1
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Yes. Yhrre are better ways of making chlorine. Electrolysis of anything is a slow process. Unless you operate at ridiculous currents.
Ca(OCl)2 and HCl make an acceptable cjlorine generator. Of course you need an addition funnel to control the rate of production. Ans a fumd hood. And
all other appropriate safety measures for working with chlorine. (Breathing Cl2 is not fun.)
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Tsjerk
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http://www.sciencemadness.org/talk/viewthread.php?tid=65712
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unionised
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| Quote: Originally posted by Keras |
I've tried that. This is a mess. Calcium acetate is little to not soluble in water, adsorbs about all the chloroform. The work-up is impossible to
carry out.
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The solubility of calcium acetate is nearly twice that of the hypochlorite.
The reaction using "bleaching powder" is well established.
eg
https://pubs.acs.org/doi/abs/10.1021/ie50042a005
https://qsstudy.com/laboratory-preparation-chloroform/
I think you probably need to distil the product as it's formed.
Whether that's easier for you than making chlorine is another matter.
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Mateo_swe
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See this reference, it contains relevant info in note1 & 2.
Organic Syntheses, Coll. Vol. 2, p.428 (1943) - β-NAPHTHOIC ACID
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Keras
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The solubility of calcium acetate decreases with rising temperature.
The problem is that you never get pure calcium hypochlorite. The purest form I found contains only 60% of it. You have to filter the solution, which
contains a significant amount of other things, like calcium chloride, etc.
To generate chlorine, just use TCCA and HCl. It’s very simple, and you get a lot of chlorine (The three of the TCCA + that of HCl). Alternatively,
drop HCl into bleach.
[Edited on 14-10-2022 by Keras]
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Junk_Enginerd
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| Quote: Originally posted by unionised |
I think you probably need to distil the product as it's formed.
Whether that's easier for you than making chlorine is another matter. |
I've tried that way and it worked great. Rather than bothering with chilling everything etc, I used a minimal amount of water to make basically a
slush of calcium hypochlorite. Then I just added the acetone dropwise and let the temperature go as high as it wanted. After a while, the chloroform
was boiling off simply from the heat of adding acetone, and could be easily collected with a condenser.
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Fery
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Junk_Enginerd - cool and clever method! Was it necessary to stir the reaction? I suppose also some part of acetone distilled out, how did you separate
it from chloroform - washing with water?
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