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Author: Subject: Acetic anhydride preparation
aliced25
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[*] posted on 21-4-2013 at 01:42


Quote: Originally posted by Sauron  
Yes, S.C> I figured that was what you meant. As it happens SiCl4 is rather easy to purchase, and not *too* expensive at $100 a kg. With a price like that I would not consider making it. After all I am paying a lot more for oxalyl chloride (a LOT more) and while I could make that, I don't bother.

The stoichiometry of SiCl4 in reaction with anhydrous NaOAc makes it attraactive, one mol SiCl4 plus 4 mols acetate giving theoretically 2 mols anhydride and in practice, 1.5 mols.

That helps compensate for the cost of reagent.

Si2OCl6 on the other hand seems to be unobtainium commercially.

Pity that SiCl4 is not more generally applicable to the preperation of acyl chlorides and anhydrides.

Anyway thanks for all the assistance.




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[*] posted on 10-7-2013 at 23:58


So far I've only read the first two pages of this thread, so forgive me if I'm bringing up something thats already been dealt with. While it seems the use of sulphuric acid as a dehydrant is unlikely to work when simply mixed with glacial acetic acid, is it possible that SO3, bubbled through the acetic acid could be more effective? Potassium peroxydisulphate, when mixed with conc. H2SO4 and heated strongly, decomposes and gives of SO3.
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[*] posted on 11-7-2013 at 01:18


I think sulfur dichloride could be used to dehydrate acetic acid.

4 AcOH + 2 SCl2 --> 2 Ac2O + SO2 + S + 4 HCl


It is common knowledge that PCl3 reacts with glacial acetic acid to form acetyl chloride, so I see no reason why SCl2 could not similarly dehydrate it much more easily. Sulfur dichloride can act as a fairly strong dehydrating agent, with water it vigorously reacts and disproportionates into elemental sulfur and sulfur dioxide.

[Edited on 11-7-2013 by AndersHoveland]
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[*] posted on 17-7-2013 at 23:35


Thanks, S2Cl2 is fairly strait forward to make isn't it?
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[*] posted on 13-8-2013 at 12:57


What about making acetyl chloride
from glacial acetic acid
and cyanuric chloride,
and then reacting acetyl chloride
with glacial acetic acid?




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[*] posted on 13-8-2013 at 13:59


From reading this thread, acetyl chloride is usually reacted with anhydrous sodium acetate, not acetic acid. I may be wrong, but I think this is because acetate is a better nucleophile than acetic acid, and the reaction goes by nucleophilic acyl substitution.



As below, so above.
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[*] posted on 13-8-2013 at 16:17


Yes, that's right. An added benefit is that sodium chloride is much easier to deal with than hydrogen chloride.
Sodium acetate is also much cheaper than glacial acetic acid.
You'd just have to stick the hydrate in the oven first to get the anhydrous salt.
You get the general idea though, and cyanuric chloride is pretty cheap.

One thing I'm not sure about, is if there are any restrictions on the purchase of cyanuric chloride in the United States.




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[*] posted on 13-8-2013 at 17:04


Quote: Originally posted by AndersHoveland  
I think sulfur dichloride could be used to dehydrate acetic acid.
Any references for that? Looks like a really weak idea.

Also, important to note that SO2 is really well soluble in AcOH and in Ac2O, so it would be a great task to get out the SO2 from this mixture. Another question: how would you get rid of the thioacetic acid what would form in high percent?

There is an article what describes the preparation of Ac2O from different acetate salts and thionyl chloride, but it's definitely not the same as AndersHoveland mentioned....
Patent DE275846
Fortschr. Teerfarbenfabr. Verw. Industriezweige, vol. 11, p. 1191




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[*] posted on 13-8-2013 at 18:10


There is a similar method to the sulfur dichloride method listed in this link.

It uses anhydrous sodium acetate and sulfur monochloride to form a sulfur linked molecule that decomposes when heated to give acetic anhydride.


In response to the question posed by white yeti, I worked with sulfur chlorides on the weekend so three days ago.
[Edited on 14-8-2013 by DrSchnufflez]

[Edited on 14-8-2013 by DrSchnufflez]




[Edited on 14-8-2013 by DrSchnufflez]




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[*] posted on 13-8-2013 at 18:41


why are all of you spending so much time asking whether or not something is possible?
The real question is whether or not it's worth doing.
Hiding behind references is just as counterproductive, even if such an absurd procedure worked, when was the last time any of you worked with SCl2 or S2Cl2?
I would guess that Anders has never worked with sulfur dichloride--being the armchair synthetic chemist that he is--and none of you would look forward to handling it, that is, if you could even buy it at all.

Don't bother considering procedures that are not even within your means. A methodical scientist will work with what he has, not what he doesn't have.




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[*] posted on 13-8-2013 at 21:37


Essigsäureanhydrid
Acetic Anhydride from S2Cl2(Include picture)
http://www.versuchschemie.de/topic,16159,-Essigs%E4ureanhydr...

[Edited on 14-8-2013 by Waffles SS]
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[*] posted on 30-9-2013 at 13:50


An unabashed necro-post, but this caught my attention when researching something completely unrelated.

I believe the 'pyrosulfate + acetate salt' dry distillation method has been brought up previously in this thread, but in case it hasn't, here is a relevant patent:

http://patentimages.storage.googleapis.com/pages/US1430304-0...

I recall one of the main reasons why this was seen as impractical was due to the toll it took on glassware, and the high temperatures required for the reaction to occur.

A procedure I recently came across to produce a somewhat manipulatable gaseous hydrochloric acid uses a microwave to heat sodium bisulfate and sodium chloride:

http://mattson.creighton.edu/MicrowaveMethod/ (Near the bottom)

I can't find any information regarding the molecular dipole moment of the pyrosulfate, but I assume it would not be so different from NaHSO4. It should therefore be fairly easy to use the method from the patent, using a modified microwave, to quite easily generate assorted anhydrides from their salts.



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[*] posted on 3-11-2013 at 14:40


someone tried that russian patent(from acetamide)? All I got was glacial acetic acid, and acetamide left in reaction flask. I tried freezing out to check if there is even a little bit of Ac2O but all of it froze :/ (aa should stay liquid) (and there was like no fraction near 139, it just started running from 120 up, and milkish smoke appeared(probably acetamide), so I stopped distillation)
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[*] posted on 3-11-2013 at 20:44


That Russian patent is bullshit!
I tried it many times and got no Ac2O
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[*] posted on 14-11-2013 at 17:20


I apologize if this has been posted before, but this is a rather long thread I had to UTFSE for a bit to find surprisingly.(EDIT: first sticky in orgranic should have been obvious :P)
Anyway...This was found @ http://web.mit.edu/semenko/Public/Military%20Manuals/RogueSc...
Not really the most journalistic site :)

(QUOTE FROM SITE)
Synthesis: Acetic anhydride is a very handy organic compound that has fallen into ill repute thanks to the drug dealers. It is technically a watched chemical, but you will only have to answer questions at gunpoint if you buy over 250 gallons. Even so, you will most likely be put on The List if you buy any, and you will have to come up with a bunch of explanations as to what you are going to do with it. Acetic anhydride is very corrosive and must be kept away from moisture, as it will decompose into acetic acid.

TLDR; Actual Syn

Into a 200-mL Florence flask, add 70 g of finely pulverized, anhydrous sodium acetate. Set the flask up for simple distillation, instead of a thermometer in the top of the flask use an addition funnel. Slowly add, by dropwise addition, 45.5 mL of acetyl chloride from the addition funnel. After half of the acetyl chloride has been added, stop the addition and stir the reaction mix with a glass stirring rod. Afterwards, continue the addition the rest of the way. If at any point during the addition some material should distill over, pour it back into the reaction flask and decrease the rate of addition to prevent this. After the addition is complete, remove the addition funnel, stop up the flask, and distill with flame or hot plate. The crude acetic anhydride thus obtained needs to be purified by distillation. Set up for a simple distillation, add 3 g of finely pulverized, anhydrous sodium acetate to the reaction flask, and then pour in the crude acetic anhydride. The sodium acetate will convert any remaining acetyl chloride into the anhydride. The receiving flask should be under a water shower for cooling. Place a large funnel (a cheap plastic one will work fine) under the flask with a tube leading to the sink, pour cold water over the top of the receiving flask. The receiving flask can also be held directly under the faucet in the sink. Commence the distillation; the yield should be about 50 g of pure acetic anhydride.
(END QUOTE)

If anyone tries this I would be curious. I don't have any acetyl chloride ATM, and I don't have time with classes to work it out theoretically, but thought I would post it in case it hadn't previously been mentioned.
If this is redundant, my apologies.

[Edited on 15-11-2013 by zenosx]




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[*] posted on 14-11-2013 at 18:50


Yes, that method (anhydride from acetate and acetyl chloride) has been discussed to death. It has also been repeatedly pointed out that unless the anhydride is needed specifically (like as a solvent or something) it is pretty pointless to make acetic anhydride from the chloride, as the latter is already a more convenient and atom efficient acetylation agent.

Apology accepted :P
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[*] posted on 17-12-2013 at 14:04


Can I just do acetic acid + P2O5 ?

I have no idea how to separate acetic anhydride and phosphoric acid though, are they miscible ?
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[*] posted on 17-12-2013 at 14:11


Quote: Originally posted by DubaiAmateurRocketry  
Can I just do acetic acid + P2O5 ?

I have no idea how to separate acetic anhydride and phosphoric acid though, are they miscible ?

I don't know if that would work, but if it did, acetic anhydride is surely a lot more volatile than phosphoric acid. It would be a high temperature distillation (about 140 C), but possible.

[Edited on 17-12-2013 by DraconicAcid]




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[*] posted on 17-12-2013 at 17:54


This may have been asked already, but this thread is so long, I can't find it.
Can acetic anhydride be synthesized by dehydration of acetic acid with CrO3?




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[*] posted on 17-12-2013 at 18:06


If I recall correctly, attempts failed using phosphorus pentoxide, which just gave char. Not sure if chromium trioxide was ever mentioned.
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[*] posted on 18-12-2013 at 02:19


Quote: Originally posted by Crowfjord  
If I recall correctly, attempts failed using phosphorus pentoxide, which just gave char. Not sure if chromium trioxide was ever mentioned.


umm why did it fail using P2O5 ?
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[*] posted on 18-12-2013 at 05:03


Try reading through the thread.



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[*] posted on 18-12-2013 at 05:26


If the Chromium Trioxide method works, I think the reaction would be 2 C2H4O2 + CrO3 ⇒ (C2H3O)2O + H2CrO4
I am worried that the Chromic Acid would decompose back into Chromium Trioxide and Water and the Water could react with the Acetic Anhydride to form Acetic Acid again.
Is this a valid method?




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[*] posted on 28-12-2013 at 00:27


Quote: Originally posted by TheChemiKid  
If the Chromium Trioxide method works, I think the reaction would be 2 C2H4O2 + CrO3 ⇒ (C2H3O)2O + H2CrO4
I am worried that the Chromic Acid would decompose back into Chromium Trioxide and Water and the Water could react with the Acetic Anhydride to form Acetic Acid again.
Is this a valid method?

What kind of a question is that? You ask and make claims at the same time, but give no reference. First give the reference for this preparation (which to me makes no sense chemically), so that we can read the article or patent and make sense of it.




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[*] posted on 29-12-2013 at 04:14


I was asking whether anyone knew IF that worked, not that it did. I was speculating about the problems with it, but saying these would or would not happen. By now, I have done as much research as I have been able to, and it seems this will not work.
This is because chromium trioxide is used as an oxidant in a solution of acetic acid. Here is a link.

[Edited on 12-29-2013 by TheChemiKid]




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