dome13
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Acetyl chloride with PCl5?
Hello guys! I did some research and it got my attention:
,,Most commonly acetyl chloride prepared by the action of phosphorus trichloride on acetic acid, since acetyl chloride boils at 51° C and it is
easily separated by simple distillation from the nonvolatile phosphorous acid. Phosphorus pentachloride reacts equally well, but in this case, the
second reaction product is phosphorus oxychloride, which boils at 107° C and the separation is not easily accomplished. However, acetyl chloride
prepared from phosphorus oxychloride is very pure with very constant boiling and does not become turbid on standing." - from PrepChem
I also found a method in "Practical organic chemistry - Julius B. Cohen", but it is for PCl3 too.
ChemPlayer has also got a video for a method wich not includes PCl3 or PCl5.
So, my main question is: Is it possible to synthetise acetyl chloride with PCl5? If yes, is there anybody, who has done this reaction?
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Loptr
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Yes, it is possible. It's one of the textbook examples of how to form an acyl chloride.
There are plenty examples on the web.
Do you have access to PCl5 or plan to use it, by any chance, or are you just asking for knowledge? It's quite reactive with moisture, and hard to keep
dry.
[Edited on 16-7-2019 by Loptr]
"Question everything generally thought to be obvious." - Dieter Rams
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chemplayer...
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We did it with PCl3 and it was pretty easy, but let's be clear - PCl3 isn't exactly easily available...
If POCl3 is a side-product of the PCl5 reaction, and POCl3 will react with acetic acid, why not just use PCl5 with a stoichiometric excess of acetic
acid and then distill off the acetyl chloride to separate?
Only catch might be if acetic acid and acetyl chloride formed an azeotrope together, but I have no idea how you would find this out other than by
trying it out. Could you live with acetyl chloride containing a small % of acetic acid for whatever your follow-up use is intended to be?
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Schleimsäure
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Using benzoyl chloride is probably one of the more cost efficent ways to obtain it, it's quite cheap and propably a bit better available than P or S
chlorides.
On the other hand acetyl chloride is available in Germany for private persons
without any restrictions:
https://shop.es-drei.de/chloride/1299/acetylchlorid-min.-98?...
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dome13
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Thanks for your replies!
Loptr: I have a possible acces to PCl5, I just have to contact the seller and I hope they sell it for an ordinary person...
chemplayer: I am planning to make acetic anhydride
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Chemi Pharma
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Quote: Originally posted by dome13  | Thanks for your replies!
Loptr: I have a possible acces to PCl5, I just have to contact the seller and I hope they sell it for an ordinary person...
chemplayer: I am planning to make acetic anhydride |
To make acid chlorides in an easier way, without the use of nasty and dangerous POCl3, PCl3, PCl5 or thionyl choride there was a thread where I've
discussed it suggesting the use of Cyanuric chloride, carboxilic acid in acetone and TEA (triethylamine) with stirring at room temperature, and
brought a research with an experimental section attached. Look at here:
http://www.sciencemadness.org/talk/viewthread.php?tid=80658&...
At the same thread @AvBaeyer Brought an interesting suggestion too, to make acid chlorides from TCCA and Triphenyl Phosphine, attaching papers too.
Look at here:
http://www.sciencemadness.org/talk/viewthread.php?tid=80658&...
@ChemPlayer also made a video on how to make acetyl chloride from acetonitrile, acetic acid and gaseous HCl that you can find here:
https://www.youtube.com/watch?v=ExDI9KUW-9Q
But if your final target is acetic anhydride, I sugest to you an easier variation, from GAA and sodium metaphosphate, like said in the Patent
attached.
Attachment: acetic anhydride from acetic acid and metaphosfate.pdf (603kB)
This file has been downloaded 445 times
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S.C. Wack
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Well then make the anhydride directly like the masterminds of yesteryear...7 parts PCl5 and 2 parts acetic acid gives acetyl chloride and POCl3, which
is then distilled with 20 parts of sodium acetate...perhaps with exotherm. It's fractionated afterwards, maybe over a little more acetate.
edit: with all due care of course...it's not clear what's the best way to mix with acetate, but as implied it would be unsurprising if things could
get out of hand.
[Edited on 19-7-2019 by S.C. Wack]
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chemplayer...
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With caution is good advice. We did do a small experiment to see if/how sodium acetate would react directly with PCl3. The temperature of the reaction
mixture on simply adding the two rose quickly to over 400C (result looked like sugar + sulfuric acid!).
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S.C. Wack
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With PCl3 and potassium acetate, over 150 years ago, the known process was 1 part dropwise to over 2 parts acetate. For POCl3, 8 parts to 10 parts
sodium acetate. It seems that they did not try to hold back the acetyl chloride that formed with a reflux condenser, but it might have been a good
idea. PCl5 and acetic acid was a recommended route to acetyl chloride for a time, says the Watts Dictionary. Here's Kekule talking about this in 1861:
https://archive.org/details/lehrbuchderorga00lacogoog/page/n...
I have not looked up the 1852 reference cited there, but either way, it's apparently not easy at all to free the anhydride from the acetate, so
there's a catch or three of course.
[Edited on 21-7-2019 by S.C. Wack]
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