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Keras
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[*] posted on 20-6-2021 at 08:26
Chloroform woes


Folks,

this might look as a newbie question, but here it is: some time ago, I made chloroform using the super-classical haloform reaction. Got around 50 ml. Stored it in a sealed bottle. When I turned back to it yesterday, there were two phases, the lower of which was red, so I supposed this might be unreacted acetone which 'polymerised' into mesityl oxide or something.

Anyways. I distilled that, collected the fraction around 62 °C, stopped maybe a tad late. As a matter of fact, the liquid I got was colourless but cloudy, with small bubbles floating atop what I considered being chloroform. The reminder, red, happened to be quite soluble in water and was easily washed away.

So I tried to redistill this. At some early point I realised that:

1. The liquid in the distilling flask was perfectly clear;
2. The bubbles had passed with the first drops of chloroform into the collecting flask (probably some sort of steam distillation phenomenon, but reversed).

So I stopped, changed my mind, took a sep funnel and, here we go, merged the lower layer with what was left in the distillation flask. Added some CaCl₂, swirled, got a very clumpy mess. Filtered that with a sintered funnel, more CaCl₂. Clear liquid, but still clumpy calcium chloride.

Took a sample of the liquid for density assess: 10 ml, 10.5g!

CCCRRRRIIINNNNGEEEEYYYY! :p

Is there any possibility that there's still some water, or is that just a LOT of unreacted acetone mixed with chloroform?

Also what is the solubility of water in chloroform?

Thanks!

[Edited on 20-6-2021 by Keras]
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S.C. Wack
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[*] posted on 20-6-2021 at 11:21


One could shake with a saturated solution of bisulfite and see what happens. The solubility of chloroform in water is rather higher than the solubility of water in chloroform. My chloroform also appeared to substantially wet CaCl2 prill in storage.



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[*] posted on 20-6-2021 at 11:30


Quote: Originally posted by S.C. Wack  
One could shake with a saturated solution of bisulfite and see what happens. The solubility of chloroform in water is rather higher than the solubility of water in chloroform. My chloroform also appeared to substantially wet CaCl2 prill in storage.


I was thinking about adding solid table salt, or a saturated saline solution to try and dry it. I wasn't expecting the chloroform to be that wet.
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[*] posted on 20-6-2021 at 11:32


About 10g/L chloroform dissolves in water according to wikipedia. On the other hand, chloroform should dissolve pretty low amounts of water. Acetone on the other hand can be miscible with quite a few materials, including water and chloroform. Due to large amount of water and small amount of chloroform, I'd assume acetone to be mostly in water phase when you're making it.

Low boiling point of about 62C and water solubility is a hint for acetone. Did you use excess (or at least surely enough) bleach? Did you mix them well?

I'd assume water (even with some dissolved acetone) should be easy to separate by decanting. The small cloudiness in chloroform (with some water) should normally clear up well when you add your drying agent (like MgSO4 or whatever).

[Edited on 20-6-2021 by Hoffit]
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[*] posted on 20-6-2021 at 11:51


Quote: Originally posted by Hoffit  

Low boiling point of about 62C and water solubility is a hint for acetone. Did you use excess (or at least surely enough) bleach? Did you mix them well?


I was warned about the difficulty of separating acetone from chloroform, so, yes, I did use an excess of bleach in order to react all the acetone. Might’ve not let the reaction properly reach its completion, though.

The chloroform is clear, there is no cloudiness at that point. But the density is way off base at 1.1 while it should be 1.5…

Is there a way to separate acetone from chloroform other than a very careful fractional distillation (56 °C/62 °C is really a small difference)? Maybe I should add more bleach… :p

[Edited on 20-6-2021 by Keras]
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paulll
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[*] posted on 20-6-2021 at 12:04


Quote:
Might’ve not let the reaction properly reach its completion, though.


Pretty plausible. Last time I did it I shook the jug a few times over a couple of hours, then put it aside at room temp. Nearly 24hrs later I gave it a shake and it went nuts, foamed up and immediately topped 40C... so I'm thinking it's not always as quick as is often suggested.
Unreacted acetone seems a better fit for the density discrepancy.
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[*] posted on 20-6-2021 at 12:46


Quote: Originally posted by paulll  
Quote:
Might’ve not let the reaction properly reach its completion, though.


Pretty plausible. Last time I did it I shook the jug a few times over a couple of hours, then put it aside at room temp. Nearly 24hrs later I gave it a shake and it went nuts, foamed up and immediately topped 40C... so I'm thinking it's not always as quick as is often suggested.
Unreacted acetone seems a better fit for the density discrepancy.


Color of the reaction mixture is a good indicator. If it's still yellow/green like unreacted bleach, it's definitely not finished. If it's clear then it's most likely finished.
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XeonTheMGPony
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[*] posted on 20-6-2021 at 13:00


I washed several times with cold water, then separated the layers, The crude was then dried over calcium chloride,

This was then distilled over fresh chloride in to a bottle to 500ml was added 2 millilitres of ethanol.

I found washing till it was no longer cloudy removed the unreacted acetone as I had the same issue with one batch.

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[*] posted on 21-6-2021 at 00:38


Quote: Originally posted by XeonTheMGPony  
I washed several times with cold water, then separated the layers, The crude was then dried over calcium chloride.


TBH, now that I think about it in hindsight, I think I began to collect the distillate around 57 °C. It seemed strange at first, but I was so certain there was nothing but chloroform therein I didn't even bother to check the BP of acetone. That 57 °C should’ve rung a bell, but I just couldn't be bothered. What an idiot I am!

I might try a new distillation, discarding everything that passes under 61 °C. Also, I did use my short apparatus, which is pretty handy to minimise losses, but doesn’t give good separation. Next time I’ll use my Vigreux column.

The reaction mixture was pretty clear when I separated it. The green tinge of bleach had pretty much disappeared. So I assume the reaction was almost driven to completion. Also, IIRC, the bleach has been stored a whole night in the freezer.

Anyways, just for information, I attach a picture of the flask in its current state.

Thanks to anyone for answering.

Attachment: phpwlTmEW (157kB)
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[*] posted on 21-6-2021 at 02:38


I had a problem with chloroform. I yesterday tried to make it with 30 ml of bleach (it was precooled, but not frozen) and 10 ml of acetone. Left it overnight but nothing happened. No separated layer. What could went wrong?
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[*] posted on 21-6-2021 at 02:49


Quote: Originally posted by BauArf56  
I had a problem with chloroform. I yesterday tried to make it with 30 ml of bleach (it was precooled, but not frozen) and 10 ml of acetone. Left it overnight but nothing happened. No separated layer. What could went wrong?


That’s wayyyy to much acetone. What is your bleach concentration? 2 or 10%?

10 ml of acetone is about 7.8 g or 0.135 mol. To get chloroform, you need three times that amount of NaClO, or 0.4 mol. That’s 30 g of pure NaClO, which, if you use a 2.7% bleach, amounts to circa 1.1 L.

Given the reaction is complete, you get 0.135 mol of chloroform, or 16 g, that is circa 10 ml. More or less the same amount of acetone you put into the bleach, except that since chloroform is soluble in water at about 8 g/L at 25 °C, you will only get half of it sunken under the water, the other half being dissolved in your litre of (former) bleach. Very low yield.

To increase the yield, you'd have to use 10% bleach, for example. You can even increase the concentration well above 10%, but then you have to modify the process completely. You can’t add the acetone all at once, because that would cause everything to boil. You have to drip it and cool everything in an ice bath.

[Edited on 21-6-2021 by Keras]
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[*] posted on 21-6-2021 at 03:07


Label says 2,2% NaClO
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[*] posted on 21-6-2021 at 03:22


See my answer about (I edited my original message)
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[*] posted on 21-6-2021 at 08:26


My stuff was clear too, till I washed it in distilled water, usually by third wash I was left with a clear lower layer.

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[*] posted on 21-6-2021 at 08:38


Quote: Originally posted by XeonTheMGPony  
My stuff was clear too, till I washed it in distilled water, usually by third wash I was left with a clear lower layer.

Ok, I’ll try that.

Also I was thinking about a dry ice bath. The chloroform should solidify, and if there is any acetone, it would remain liquid.
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[*] posted on 21-6-2021 at 14:29


Quote: Originally posted by Keras  
I was thinking about adding solid table salt, or a saturated saline solution to try and dry it. I wasn't expecting the chloroform to be that wet.


I was of course talking about confirming the presence of acetone.

Quote: Originally posted by Keras  
Next time I’ll use my Vigreux column.


It would surprise me if acetone and chloroform can be separated with a Vigreux; it should do better with removing chloroform from water.

BTW trivia...chloroform was in the US news last week...one Zack Lee (why not Steev or Jarruld?) Smith of Bronson IA abducted a woman and was apparently successful in deploying the homemade substance against her. We know this only because she was later able to escape her imprisonment...I have to wonder where he learned to make enough of it to use (the "internet" obviously)...such unsavory stories bother me greatly...




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[*] posted on 21-6-2021 at 14:59


Quote: Originally posted by S.C. Wack  

BTW trivia...chloroform was in the US news last week...one Zack Lee (why not Steev or Jarruld?) Smith of Bronson IA abducted a woman and was apparently successful in deploying the homemade substance against her. We know this only because she was later able to escape her imprisonment...I have to wonder where he learned to make enough of it to use (the "internet" obviously)...such unsavory stories bother me greatly...

Uhm... I have to admit I might have picked up a book from dean koontz at the public library...
And the figure in that book made, in a motel bathroom, chloroform from "chlorinated lime" from a hardware store and "acetone from an artist shop", and I actually felt soiled after reading this and put the book away.
Shame on me!

But it appears to be quite common knowledge in the meantime?
Even though, the use of it is still fictional, with immediate knockout effects and so on...
I wouldn't be surprised if this encourages some sick people to try it out themselves.
I know of such a case from germany, really hardcore and evil, resulting in a dead (minor) victim...
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[*] posted on 22-6-2021 at 01:12


I mean, as far as Wikipedia says, it takes about 5 minutes of continuous inhalation to trigger the anaesthetic effect, and then the supply must be continuous in order to sustain it. It seems that the use of chloroform to perform abduction is really cumbersome. Unless you have access to medical hardware.
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[*] posted on 22-6-2021 at 08:47


Quote: Originally posted by BauArf56  
Label says 2,2% NaClO


This would produce at most 0.35mL of chloroform; why are you even surprised? You used 50 times as much acetone as you needed as well, and there's also so much water present that your product would never separate.

Keras, my advice to you on your next attempt is to use frozen bleach, add molar equivalent (taking into account that you need 3 moles of hypochlorite per mole of acetone of course) or a slightly lower amount of acetone, then close and fully invert the container once or twice as soon as the entire bleach mass is liquid, and then allow it to sit for 12-16 hours. Wash the chloroform with brine, distill, and you're done. If you don't want to distill it, at least allow it to sit atop the brine for a few hours until total separation is noted.
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[*] posted on 22-6-2021 at 08:56


Separating something that has a 5-6C difference in boiling points is not easy by distillation. Even if you discard everything below say 61C, you'll get a huge loss (considerable vapor pressure for chloroform below boiling point). Also at 61C you'll still get some acetone in it. (your purity requirements may accept low amount). Similar to say distilling alcohol, even at 90C you still get some alcohol distilled and a lot of water in it. Mixtures do not start to vaporize at boiling points of components.

If you happen to have a reflux distill head and a packed column that could be done. It could be a nice exercise. Most people do not have such distill heads and they seem difficult to find for a reasonable price. I've been looking for one quite some time.

Bisulphite adduct is a lot easier way to remove acetone, especially if the volume is not too large.

[Edited on 22-6-2021 by Hoffit]
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[*] posted on 22-6-2021 at 10:29


I have a surprisingly good Vigreux column, but I can easily pack it by using glass wool and filling it with small glass beads.

What do you exactly mean by ‘reflux still head’?

I know that I would get some chloroform in the acetone, but I figured most of the acetone would have been boiled away before reaching 62 °C.

In any case, it’s probably worth trying, but unfortunately I won’t be able to do that before mid-July :(
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[*] posted on 22-6-2021 at 15:39


Having done this reaction (and many others) every which way, I suggest sticking to the script written in lab manuals; their directions were not chosen for inconvenience, it turns out. One may find fractional distillation theory also, and even illustrative quotes such as this from Vogel:

An ordinary 1-cm tube 1 metre long might be equivalent to only one theoretical plate, while the same tube filled with a suitable packing can give the equivalent of twenty of more theoretical plates. A column with twelve theoretical plates is satisfactory for the practical separation of a mixture of benzene and toluene (30C); where the two components of a mixture differ in b.p. by only about 3C, a column with approximately 100 theoretical plates would be required.

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[*] posted on 23-6-2021 at 02:31


Lol. I’m aware of that.

But that doesn’t forbid doing a fractional distillation to remove as much acetone as possible, then use bisulphite to remove what's left of it!

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[*] posted on 23-6-2021 at 09:27


Noone mentioned this but water and chloroform produce an azeotrope that is 97% chloroform and 3% water.
It boils at 53.3C. If you are using 2% bleach, you probably want to recover the portion in the water as it will be substantially all of the product (10+g/L). Salting it out using sodium chloride is the usual method but distilling is also possible.

A packed column with 10:1 reflux would be good for the fractional distillation.
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[*] posted on 24-6-2021 at 07:21


I don’t think water will be a problem here. But yes, thanks for mentioning this, especially since it involves so little water.

I used 10% bleach.

I wonder if I couldn't use concentrated homebrewed bleach made by bubbling chlorine gas into a sodium hydroxide solution (lye). However, I’m afraid the heat produced by the reaction would instantly boil everything off.

10:1 reflux? You mean 10 plates?
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