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njl
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Yes I believe in earlier pages of this thread. Sometimes a pain to read through, but I remember it being discussed. Also, 1000th post 
Reflux condenser?? I barely know her!
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Keras
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Wow. I swear I didn't even notice 
Besides, is it possible to get acetyl chloride by bubbling HCl into acetic anhydride? Just curious. Something I might attempt early next week.
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Metacelsus
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According to Wikipedia yes: https://en.wikipedia.org/wiki/Acetyl_chloride#Synthesis
You could separate the acetyl chloride by distillation.
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njl
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Keras, if you are going to try that would you perhaps also try the MeCN/HCl reaction for generating acetyl chloride? Assuming you have MeCN that is.
The procedure is quite similar to Ac2O/HCl.
Reflux condenser?? I barely know her!
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Keras
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Quote: Originally posted by njl  | | Keras, if you are going to try that would you perhaps also try the MeCN/HCl reaction for generating acetyl chloride? Assuming you have MeCN that is.
The procedure is quite similar to Ac2O/HCl. |
Yeah, I have acetonitrile. What I lack most is time, alas :/ Especially since I live one hour away from my lab.
The MeCN/HCl reaction you mention is described Chemplayer's video, right?
[Edited on 3-5-2021 by Keras]
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njl
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Yes it is, but experiments done by users on another forum showed that Chemplayer didn't use nearly enough HCl gas, or allow the reaction to run for
long enough. See my reply in this thread from 4/29/21 for more info.
Reflux condenser?? I barely know her!
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Keras
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| Quote: Originally posted by njl | | Yes it is, but experiments done by users on another forum showed that Chemplayer didn't use nearly enough HCl gas, or allow the reaction to run for
long enough. See my reply in this thread from 4/29/21 for more info. |
OK. I’ve dug out the original publication in the Comptes rendus de l'Académie des Sciences (being French helps for this once) – the mixing must
be done at 0°C and the solution saturated with HCl must be left standing for 24 h in a closed vial. The author claims to have obtained a large number
of acetamide chlorhydrate crystals and the corresponding amount of AcCl.
If you want to see it for yourself, it’s here.
[Edited on 3-5-2021 by Keras]
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S.C. Wack
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| Quote: Originally posted by Keras | | Besides, is it possible to get acetyl chloride by bubbling HCl into acetic anhydride? Just curious. Something I might attempt early next week.
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It's all been posted before.
https://www.sciencemadness.org/whisper/viewthread.php?tid=32...
https://www.sciencemadness.org/whisper/viewthread.php?tid=77...
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Keras
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| Quote: Originally posted by njl | | Yes it is, but experiments done by users on another forum showed that Chemplayer didn't use nearly enough HCl gas, or allow the reaction to run for
long enough. See my reply in this thread from 4/29/21 for more info. |
Wikipedia reports the yield of this reaction to be very low, typically under 40%.
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njl
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Well half of the acetonitrile is consumed as acetamide HCl. The advantage to this reaction isn't yield it's that the procedure is so simple, and
yields only the volatile product and a non volatile side product. If you really wanted to you could even recycle the acetamide back to acetonitrile.
Reflux condenser?? I barely know her!
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Keras
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| Quote: Originally posted by njl | | Well half of the acetonitrile is consumed as acetamide HCl. The advantage to this reaction isn't yield it's that the procedure is so simple, and
yields only the volatile product and a non volatile side product. If you really wanted to you could even recycle the acetamide back to acetonitrile.
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To be honest, I have a hard time figuring out a reasonable pathway for this reaction. Admitting the acid is transformed into the acyl chloride, as
seem to be the case, there is probably an H⁺ attack on the double-bound O, in which case OH⁻ would be the leaving group, (but that’s very
unlikely?).
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njl
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I think it works via addition of HCl to the nitrile to form an imidoyl chloride, this reacts with AcOH to give the mixed imidoyl/acetic anhydride,
addition of chloride to the acetyl group and elimination of the bridging oxygen to give acetyl chloride and an "imidic acid" which then tautomerizes
to the amide.
Edit: see the Pinner reaction for more details. Although it is conducted with a nitrile, acid, and alcohol, the mechanism is probably similar where
the alcohol is replaced with AcOH.
[Edited on 5-5-2021 by njl]
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Keras
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| Quote: Originally posted by njl | Edit: see the Pinner reaction for more details. Although it is conducted with a nitrile, acid, and alcohol, the mechanism is probably similar where
the alcohol is replaced with AcOH.
[Edited on 5-5-2021 by njl] |
Will have a look.
So, I decided to try this reaction today. The setup is in the first attached picture. Dropping funnel with ~ 100 mL of concentrated sulphuric acid,
250 mL two-neck RBF filled with 60 g NaCl, second neck leading to a CaCl₂ tube. The outlet is connected to a bent glass tube (that I made myself
using straight tubing, a glass cutter tool and my blowtorch, I’m pretty proud of that) running through a rubber cork plugged into the first outlet
of a Claisen adapter. The tube plunges into a small, 50 mL RBF containing 0.3 mole of each acetonitrile and glacial acetic acid (circa 15 mL each),
the RBF being immersed in an ice/salt bath. The second outlet of the Claisen adapter is connect to a second CaCl₂ tube.
I calculated the HCl generator for a 2 mol output, way more than the stoichiometric amount (0.6 mol).
A gentle current of argon was bubbled into the solution while the HCl generator was starting, to clear residual moisture (the weather was rainy).
At no point during the HCl bubbling did the temperature rise over -15 °C (see second picture).
But the HCl gas generator turned out to be pretty unreliable. I had a very slow stream of HCl out. Even when the addition of all the sulphuric acid
was over, I got the feeling that very little had run into the small RBF. I dismantled the apparatus, transferred the contents of the RBF into a vial
that I stored in the freezer. So far, (about 6 hours later), I still have nothing apparent. There was a lot of unreacted acid in the HCl generator,
which took a while to neutralise properly with both lye and sodium bicarbonate. I didn't heat the HCl generating flask, and I’m sure that was a
mistake, because the reaction didn't generate a lot of heat, was slow, and I had to open the generator every so often to break up the mass of ?sodium
bisulfate? that formed and swirl the flask to get it run more vigorously.
I won’t be able to return to my lab before next Tuesday, but in the meanwhile the flask with the reactants is secured in the freezer. I probably can
pick up where I left, assuming I can assemble a more efficient HCl generator. If anyone had a recipe for a good, reliable HCl generator, I’m all
ears
[Edited on 11-5-2021 by Keras]
[Edited on 11-5-2021 by Keras]
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Keras
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EDIT: I was told that the flask is now full of crystals. I suppose it takes a while for the reaction to progress at -18 °C. I wonder, btw, if the
reaction starts with the bubbling at all. Probably the bubbling gets HCl dissolved in the mixture, and it’s only after the bubbling is complete that
the reaction picks up. If this is true, then it’s important to keep the flask cooled in order to avoid losing HCl.
By the way, I got no HCl escaping from the second CaCl₂ moisture trap, so I guess everything I generated got dissolved.
I’ll check what I get next Tuesday.
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clearly_not_atara
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What kind of HCl generator makes sodium bisulfate?
There are two HCl generation methodologies I know about; both involve adding azeotropic hydrochloric acid to something. "Something" is either
concentrated sulfuric acid or anhydrous calcium chloride. The latter technique is significantly cheaper, but can give an unreliable gas generation
rate, so H2SO4 is preferred when possible.
I also wonder if you could use a slurry of CaCl2 and 85% H3PO4, or if this would give undesirable side-reactions, or condense into an intractable
solid mass.
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Keras
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NaCl + H₂SO₄ → NaHSO₄ + HCl
| Quote: Originally posted by clearly_not_atara | | I also wonder if you could use a slurry of CaCl2 and 85% H3PO4, or if this would give undesirable side-reactions, or condense into an intractable
solid mass. |
Never tried that. Don’t have enough CaCl₂ at present to give it a go.
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Keras
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OKKKKKKK. So, I went back to my lab, and checked on the acetic acid/acetonitrile/HCl process. The bottle I'd left the mixture in was indeed full of
crystals (as a reminder, it stayed a full week in the freezer at -18 °C). I prepared it for vacuum filtration but before I could do anything my
vacuum tube, which is unnecessarily unwieldy, made the Erlenmeyer flask trip and the funnel broke :/ I will have to buy another.
That was not a huge problem, apart from the outlay of 40 euros just for being clumsy, since I was able to directly decant the liquid from the crystals
(and thus spared my other grade-4 Büchner funnel in the process). I washed the bottle and the crystals with a bit of cold ether, collected everything
into a small Erlenmeyer flask, and set up for distillation. The collected liquid fumed strongly, but I was not able to tell whether it was because of
diluted HCl that was being released as the mixture warmed, or because of acetyl chloride in the mix.
Distillation was very slow (one drop every three or four seconds). The first drops were collected around 30 °C, which was expected (ether). That
'head' also fumed, so I suppose ether carried away a bit of HCl. After like 5 ml of ether had passed, and I was already ¾ hour into it, the temp
began to rise steadily, but it was really a pain. I switched the hotplate I used for a heating mantle and carried on. Unfortunately, the temp here
jumped all the way from 30-35 °C to 80-82 °C, the boiling point of acetonitrile. There was absolutely no pause at 51, the b.p. of acetyl chloride.
Just to be certain, I continued collecting the fraction at 82, and when it died out I was left with a flask visibly full of acetic acid, with a slight
brownish tinge.
So, the yield was zilch. Traces, maybe, of acetyl chloride, but nothing I could separate from the starting materials. I dripped a few drops of the 30
°C fraction into water, and there was a slight haze of HCl emitted. As a clincher, I added a few drops of n-butanol, waited a bit, and tried to smell
the result. There was definitely the characteristic aroma of butyl acetate, but it was very faint.
Yet, there were crystals of acetamide-hydrochloride. A few grams, maybe (I didn't even bother to weigh them).
The weather is quite bad over here in Western Europe these days, but I doubt that even that high level of atmospheric moisture could’ve turned all
the acetyl chloride back into acetic acid and hydrogen chloride. I had, however, difficulties with my HCl generator, so I suspect the quantity of HCl
that was actually bubbled into the initial mixture was way beyond what I hoped.
I don’t think ether reacts with acetyl chloride.
I’m going to redo the experiment, but this time I plan to warm the HCl generator so as to push the reaction between sulphuric acid and salt as far
as I can.
[Edited on 18-5-2021 by Keras]
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clearly_not_atara
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I don't think that dripping concentrated sulfuric acid onto table salt is a very good HCl gas generator. It would probably be better to use one of the
other two methods with a drying tube. I can't really speak from experience as I've never done it that way. Warmer will help, of course.
It appears there is AcCl entrained in your ether. Probably not a lot, but if you want to isolate it, you could try stirring the ether fraction with
some anhydrous potassium or sodium acetate (the former is easier to dry) and re-distilling; the much larger bp difference with Ac2O will surely
separate the two.
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S.C. Wack
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Can you think of a reason for why this might be; while technically may not be true?
[hint: it's obvious]
The quality of clan lab chemistry has really fallen (along with Rome) in the past 20 years...I was mistaken to believe that someone might read the books I
scanned...C.W. Scheele would be even more disappointed with this...BTW the UK Alkali Act of 1863 was the first legal control of chemical emissions
(target: hydrogen chloride from salt and sulfuric acid)
[Edited on 18-5-2021 by S.C. Wack]
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clearly_not_atara
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When you are dehydrating muriatic acid, the residue in the rxn flask can be heated to regenerate... more H2SO4 (unpleasant, to be fair) or more CaCl2
(easy). But if you are reacting H2SO4 with salt, you lose your reagent. See the difference? And conc. H2SO4 is a thing to come by these days --
granted dehydrating it is no fun, but at least you aren't starting from 15%.
I am of course aware of the reaction, I just wasn't aware that someone would choose it.
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Keras
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So there are several possibilities: the first one is kinetics: since the mix was 'created' and left at -18 °C circa, it is possible that at this
temperature the reaction is crawling.
Next, insufficient HCl being bubbled into the mix, or water vapour that made its way even though I set up a CaCl₂ trap, which did not appear to
catch any water whatsoever (the pellets were still very dry when I dismantled it).
Finally, the distillation might’ve gone awry because of an azeotrope Et₂O/AcCl. Separation between the two theoretical b.p. was fair (35 °C for
Et₂O, 52 °C for AcCl), I should've got both, even without using a Vigreux column.
Beyond that, apart from bad reagent quality or something of the same ilk, I’m at a loss.
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Keras
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| Quote: Originally posted by clearly_not_atara | | When you are dehydrating muriatic acid, the residue in the rxn flask can be heated to regenerate... more H2SO4 (unpleasant, to be fair) or more CaCl2
(easy). But if you are reacting H2SO4 with salt, you lose your reagent. See the difference? And conc. H2SO4 is a thing to come by these days --
granted dehydrating it is no fun, but at least you aren't starting from 15%. |
I agree that sulphuric acid is going to be a dainty in a few months. However, I still have 9 L left of it, and I recently bought from my local
hardware store a couple of leftover bottles of drain cleaner (~70% concentration) from which I should be able to generate more than one L of
concentrated stuff (or use directly in a generator), as well as 3 bottles of 37% grade, that I could use to, say, make azeotropic hydrobromic acid.
I’m not sure using sulphuric acid to dehydrate 36% HCl is very efficient. You’re right in that it doesn’t waste the sulphuric acid, however.
Yet, reacting sulphuric acid with salt generates sodium bisulphate, from which you can regenerate SO₃ by heating, which you can feed into c.
sulphuric acid to form more.
2 NaHSO₄ → Na₂SO₄ + SO₃ + H₂O
So you lose acid, but half of what you expected, provided you collect the residue. Besides, sodium bisulphate is cheap and easy to acquire, so as long
as you have some sulphuric acid left, you can easily generate oleum that you dilute to get more sulphuric acid.
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clearly_not_atara
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Right, but you're comparing all of these distillations to heating a jar on a hot plate for a few hours.
| Quote: | | I’m not sure using sulphuric acid to dehydrate 36% HCl is very efficient. |
It is the standard HCl gas generation methodology. It works at low temperature and gives a consistent flow rate. What more
could you ask for? See e.g.:
https://www.sciencemadness.org/whisper/viewthread.php?tid=90...
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Keras
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In my case, I have only 23 % azeotropic HCl, so I'd have to concentrate it, meaning I'd have to generate HCl to then generate HCl :p
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S.C. Wack
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Can acetyl chloride be distilled from a mixture with acetic acid?
There are a few lab manuals that mention salt with conc. HCl (Fieser, the Organikum) and of course it is standard for cookbooks (Uncle Fester,
Strike), but the majority of directions either do not use HCl or it is mentioned as one possibility; when it appears it's often in a more complicated
setup not using salt. (e.g. Vogel, who also has the oft-mentioned ammonium chloride)
[Edited on 19-5-2021 by S.C. Wack]
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