Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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]
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
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.
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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.
|
|
|
Hoffit
Harmless
Posts: 21
Registered: 12-8-2019
Member Is Offline
Mood: Excited
|
|
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]
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
| 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]
|
|
|
paulll
Hazard to Others
Posts: 112
Registered: 1-5-2018
Member Is Offline
Mood: It's fine. Really.
|
|
| 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.
|
|
|
monolithic
Hazard to Others
Posts: 436
Registered: 5-3-2018
Member Is Offline
Mood: No Mood
|
|
| 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.
|
|
|
XeonTheMGPony
International Hazard
Posts: 1640
Registered: 5-1-2016
Member Is Offline
Mood: No Mood
|
|
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.
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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)
This file has been downloaded 270 times
|
|
|
BauArf56
Hazard to Self
Posts: 68
Registered: 22-8-2019
Location: between the moon and the sun
Member Is Offline
Mood: energetic
|
|
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?
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
| 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]
|
|
|
BauArf56
Hazard to Self
Posts: 68
Registered: 22-8-2019
Location: between the moon and the sun
Member Is Offline
Mood: energetic
|
|
Label says 2,2% NaClO
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
See my answer about (I edited my original message)
|
|
|
XeonTheMGPony
International Hazard
Posts: 1640
Registered: 5-1-2016
Member Is Offline
Mood: No Mood
|
|
My stuff was clear too, till I washed it in distilled water, usually by third wash I was left with a clear lower layer.
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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.
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
| 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.
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...
|
|
|
karlos³
International Hazard
Posts: 1520
Registered: 10-1-2011
Location: yes!
Member Is Offline
Mood: oxazolidinic 8)
|
|
| 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...
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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.
|
|
|
Amos
International Hazard
Posts: 1406
Registered: 25-3-2014
Location: Yes
Member Is Offline
Mood: No
|
|
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.
|
|
|
Hoffit
Harmless
Posts: 21
Registered: 12-8-2019
Member Is Offline
Mood: Excited
|
|
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]
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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 
|
|
|
S.C. Wack
bibliomaster
Posts: 2419
Registered: 7-5-2004
Location: Cornworld, Central USA
Member Is Offline
Mood: Enhanced
|
|
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.
Need video? OK...I Fought In A War
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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!
|
|
|
macckone
Dispenser of practical lab wisdom
Posts: 2168
Registered: 1-3-2013
Location: Over a mile high
Member Is Offline
Mood: Electrical
|
|
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.
|
|
|
Keras
National Hazard
Posts: 937
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
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?
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
