peppovsky
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HCl solution in Diethyl-Ether
Apparently Sigma-Aldrich and other chemical companies sell HCl solution in diethyl-ether (normally 1 or 2 N). It makes sense, since HCl is somewhat
soluble in diethyl-ether. How is it made? Do they bubble dry HCl gas through the ether? It's probably not just mixing concentrated HCl and ether,
since this might hydrolyze the ether to ethanol and ethyl-chloride (although Cl- is a weak nucleophile - anyway I know this is usually done with
H2SO4).
More practical - I was thinking, If I had ether and conc. HCl (the usual 32%/12M), I would dry the ether with excess CaCl2, and add conc. HCl
solution (while everything is kept cold to avoid as much hydrolysis as possible), thus generating HCl gas in-situ, that will dissolve to some extent
in the ether (and all the CaCl2 that is already in and is still dry, will effectively dry the remaining organic+HCl solution...).
Does this sound plausible?
(I prefer consulting the forum before trying it with perhaps bad results and/or generating ethanol+ethyl chloride...)
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Lambda-Eyde
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This has been discussed before. See the attached files.
Attachment: HCl in ether prep.pdf (486kB)
This file has been downloaded 2680 times
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peppovsky
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I see. I honestly haven't noticed this topic while searching, so I'll try a better search next time.
Some final questions though - Should I expect heat liberation when mixing the conc. HCl and the ether (that is - before adding the right amount of
MgSO4)? What about liberation of dry HCl gas? Should I mix them on an ice bath?
Anyway, Thanks a lot for those files!
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Nicodem
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Mixing approximately equal volumes of conc. HCl(aq) and diethyl ether forms a clear monophasic solution and the mixing is not particularly exothermic.
On dilution or neutralisation the solution again separates into two phases.
On the other hand, dissolving HCl in diethyl ether is very exothermic and cooling with ice must be used. The heat capacity of diethyl ether is low so
the heat released rapidly increases the temperature to the already low boiling point. It takes a long time to saturate the solution as HCl is very
well soluble in ether. When I needed such a solution I put a stir bar in a 2/3 full 1L diethyl ether bottle, immersed it in a bucket of ice and kept
slowly introducing HCl with a tube while stirring intensively. You figure out when it is saturated when fumes of HCl start escaping the bottle (in a
fume hood obviously!). Monitoring the proper rate of dissolution with a thermometer is obviously a good idea. It should be slow enough so that the
bubbles don't even reach fully the surface, but fast enough so that you don't get suck backs. You can then titrate to determine the concentration and
store it in a refrigerator. Commercial HCl/Et2O is irrationally expensive, so where I work we never buy it and I never heard of anybody who does.
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smuv
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The easiest way to make an appreciably dry solution of HCl in ether, is to take 4 parts ether and mix it with 1 part conc HCl in a container that can
be sealed quickly and withstand some positive pressure. Cool everything on an ice bath for a while. Then add a large excess of MgSO4 and seal the
container. Shake the container (so the MgSO4 doesn't clump on the bottom) periodically for a few minutes. Next decant the Ether from the bulk of the
MgSO4. Add MgSO4 to the decanted product and let it sit a while in the cold. Then Filter the solution through a plug of cotton to obtain ether dry
enough to precipitate amines as freely flowing salts.
CaCl2 does not work well for this, there are always 2 layers.
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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peppovsky
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Nicodem - what do you mean by "slowly introducing HCl with a tube"? I was thinking about doing so in an open Erlenmeyer flask (with magnetic stirring
of course), and adding the conc. HCl via a pipette (everything on an ice bath, obviously). Then shake it with enough MgSO4.
What is the glassware setup you recommend?
[Edited on 27-5-2010 by peppovsky]
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stygian
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HCl is a gas.
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peppovsky
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oh, he meant bubbling HCl into the solution. I see. I thought he was still talking about the conc. acid
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zed
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On the other hand, if you just need that "Dry" HCl for something simple, like forming the dry HCl salts of amines....You can do the whole thing in one
flask or beaker.
Simply dissolve your amine in Et2O or Methanol etc., and bubble dry HCl gas through your solution (use a trap to prevent suck-back). Continue, until
no further Amine HCl precipitates. While free Amine remains in the solution, very little HCl gas can escape.....Once the Amine is salted out, and
the solution is saturated with HCl, excess HCl gas will escape from the solution. If you lack a good fume hood, a large inverted funnel attached to
a water-aspirator, will whisk away excess that HCl, and flush it down your drain.
The standard method for generating HCl gas, is by dripping Concentrated Sulfuric Acid onto Rock Salt. Works very well. Cheap and easy.
If it works out that you don't actually need to use Ether...All the better. When I can alternately use some other solvent, I generally do. Ether
isn't really terrible, but it's fussy. It's a low boiler, it forms explosive mixtures with air, and it has a penchant (if neglected) to form
explosive peroxides.
[Edited on 29-5-2010 by zed]
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peppovsky
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Actualy, I'm interested in the HCl-in-Ether method because bubbling dry HCl gas is awfully dangerous. Furthermore, you forgot to mention the face that
between the trap and the beaker to which you bubble your HCl into, you should place a CaCl2 tube, otherwise the gas is wet (When I did it, it was
using the HCl-CaCl2 method, so I'm not sure about your suggestion... and I'm not to excited about dealing with conc. H2SO4 either  ).
Any way, I tried the HCl-in-Ether method and found it to be working, although one thing is extremely annoying (and it was the same when I used the dry
gas bubbling method) - the Amine-salts tend to stick to the bottom of the glassware, and be generally gooey. I've tried washing it with some dry ether
(without HCl in it), and it helped only a bit. I should note in the HCl-in-Ether solution preparation I made sure the thing is damn dry (I've dried it
three times with MgSO4).
p.s. I'm well aware of the dangers of ethers, and I'm planning to purchase a starch-iodine paper and some FeSO4 to make sure these never form.
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zed
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Bubbling dry HCl gas through a solvent is not very dangerous. Nor is working with concentrated H2SO4. A simple water aspirator vacuum pump,
attached to an inverted funnel, will whisk away any stray HCl gas. Though working in a fume hood
is better.
100% H2SO4 can burn the living crap out of you, so it should be treated with great respect. But, on the list of chemist's fears....Sulfuric Acid
doesn't rank very high. Wear a face shield, gloves, labcoat, and have a safety shower nearby. Should be no problem
Also, since Concentrated(100%) Sulfuric Acid contains no water, and Rock salt contains no water, HCl gas generated by their reaction....contains no
water! It does not need to be dried.
Gooey products? Either your Amines are wet or contaminated, or your Ether is wet. It has become a commonplace practice to re-cycle ether. It's
none-to-easy to get it thoroughly dry. There is a thread on that subject somewhere here.
Dry methanol is cheap, and fairly easy to work with. I can recall reacting Amines with dry HCl gas in cold methanol. Came right out of
solution....Clean and dry.
Might be suitable for the material you are working with, or it might not.
As always, I suggest seeking out someone with greater lab experience as a mentor, if you are concerned about using some particular chemical or
procedure. A trip to the local college chemistry dept., can be helpful.
[Edited on 30-5-2010 by zed]
[Edited on 30-5-2010 by zed]
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peppovsky
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First of all, I'm a year from getting my undergraduate degree in chemistry from the local college, and I've done organic chemistry labs (just calming
my ego  ).
The problem with seeking people there with more experience then I have, is that I don't think they'll be too keen on helping someone with his Amines
experiments
So, unfortunately, all my learning in this subject will have to be done by myself...
In the college labs I used the inverted-funnel method a few times, when HCl (or even HBr at one time) came out of the solution. But when I did it, it
was attached to the top of a condenser that was on-top of a RBF that was doing some reaction that produced HCl/HBr. I'm not really sure, with your
suggestion, what does the aspirator has to do with the funnel, and how do I connect everything: say, I have a gas-generating flask, connected to a
trap, connected to the flask I wish to bubble the gas into, which itself is open to the inverted-funnel using a tube, and the air via a CaCl2 tube.
Where is the aspirator located in all that?...
btw, my big problem with conc. H2SO4 is actually keeping the bottle. It's just doesn't seem too much safe.
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smuv
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To avoid gooey amines from coming out of solution, add an excess of HCl in ether to a solution of the amine in a halogenated solvent (DCM, CHCL3
C2Cl4, etc). Make sure there is enough halo solvent so the amine HCl does not precipitate (amine HCl's are pretty soluble in these solvents). Then
with a dropping funnel or other thing you can use to slowly add solvent, add ether dropwise over a long span of time. The amine salt should come out
crystalline without goo (at least in my experience).
"Titanium tetrachloride…You sly temptress." --Walter Bishop
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watson.fawkes
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Quote: Originally posted by zed  | | Also, since Concentrated(100%) Sulfuric Acid contains no water, and Rock salt contains no water, HCl gas generated by their reaction....contains no
water! It does not need to be dried. |
While 100% H2SO4 is certainly available, the more common concentrated
product is 98.5%, as that's the typical target concentration for the absorption tower in the contact process for manufacture of the acid. In addition,
pure H2SO4 is very hygroscopic (itself used as a drying medium, where appropriate) and so will pick up atmospheric moisture unless proper
dry-atmosphere techniques are used. Furthermore, as the H2SO4 + NaCl reaction proceeds, the ratio of H2O to H2SO4 increases, and so the product gas
becomes wetter over time.
For all these reasons, it's just easier to use a drying stage for the output gas. The alternate is to react with oleum, which can scavenge residual
water, but building and operating a drying chain is cheaper than buying oleum for this purpose.
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peppovsky
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| Quote: Originally posted by watson.fawkes | [...]Furthermore, as the H2SO4 + NaCl reaction proceeds, the ratio of H2O to H2SO4 increases, and so the product gas becomes wetter over time.
For all these reasons, it's just easier to use a drying stage for the output gas. The alternate is to react with oleum, which can scavenge residual
water, but building and operating a drying chain is cheaper than buying oleum for this purpose. |
And anyway, even if it was dry when first reacting, there's a lot of moist air in between the reaction vessel and the solvent vessel, where it can
absorb moisture...
This is why I believe a CaCl2 tube is a must.
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zed
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Use a CaCl2 drying tube if you wish to. I've never found it necessary.
98.5% H2SO4 is dry enough.
Use Ether if you wish to. I wouldn't, but I am me, and you are you.
Think of the glassware set-up as being two separate set-ups. They are not mechanically connected.
One set-up to generate HCl gas, and One set-up to scavenge any excess gas that escapes your Amine solution.
The inverted funnel and the aspirator...remove excess HCl gas. A trap isn't a bad idea. In the event, that something goes wrong with the aspirator,
the trap will catch any water that initially may backup through your funnel line.
Equally critical, is a trap between your H2SO4/NaCl and your gassing tube.
Without a trap, if gas generation slows, and you are inattentive, your HCl hungry Amine solution, can back-up into into the flask where your H2SO4 and
NaCl are reacting. Also, your reacting H2SO4 and NaCl, could "foam up" and the foam could reach your CaCl2 tube, or even your Amine solution. You
don't want that.
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Chemi Pharma
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I have bubbled HCL gas into an Diethyl ether solution with an amine and I got the amine hydrochloride precipitated at the bottom, but also two layers
too, instead the expected one layer with HCL dissolved in Diethyl ether.
What can it be? I separate the layers in a separate funnel and tested the lower layer. This react with carbonate with bubbles as an acid and burn with
a flame like Diethyl ether.
I don't know what the two layers could be. I suppose the higher layer is diethyl ether satured with HCL cause the fumes, but I still don't know what
the bottom layer is. I only know that fumes HCL, react with carbonate like HCL and burn like diethyl ether.
Someone could help me to solve this mistery?
[Edited on 29-10-2018 by Chemi Pharma]
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Assured Fish
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Necropost much.
Nevertheless, what was the source of your ether, could the component be ethanol?
Maybe some kind of ether/water/HCl mixture.
If i were you i would attempt to discern the boiling point of your mystery component in a test tube, if it doesn't decompose violently then perhaps a
small scale distillation to follow.
Sufficiently advanced science is indistinguishable from madness.
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Chemi Pharma
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Hi @Assured Fish,
I used an extra purified and anhydrous comercial diethyl ether and an extra full calcium chloride tube to filtrate the HCL gas generated by an
reaction between sulfuric acid and anhydrous sodium chloride. No aquous HCL was used, and the silicone tubes were completely destroyed after a day
from the reaction. I had to change all the silicone tubes envolved by thick rubber tubes, cause PU tubes I also tried were destroyed too by the
anhydrous HCL gas.
Then, I think no water pass to react with the diethyl ether tube. I was thinking about an SN1 reaction, giving Ethyl alcohol and ethyl chloride, that
probably escapes cause it's lower boiling point (I worked with room temperature all time). This way, I probably have ethyl alcohol riched with HCL as
the bottom layer, and cause this, the bottom layer burns with a yellow/blue flame like diethyl ether, I guess.
But it's a good idea try to measure the boiling point of the bottom layer mixture, like you've said, trying to identificate what it is. Thank you for
your reply.
[Edited on 31-10-2018 by Chemi Pharma]
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