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MrDoctor
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Quote: Originally posted by Waffles SS  |
Anyway I want to introduce another interesting method for synthesis carboxylic acid anhydride by electrolysis.
Electrolysis by graphite anode and steel cathode of mixture:
Carboxylic acid + acetonitrile + catalyst (potassium thiocyanate) make anhydride
[Edited on 18-8-2025 by Waffles SS] |
I would have eaten my desk out of pure rage, had that paper been published in like 1970 or something and yet again such a valuable piece of research
had been sat on for 50 years before we (amateur chemists) found out about it. But luckily it was published in 2022, so my desk remains largely bite
free.
I am currently in possession of some tetrabutylammonium bromide, and can easily concentrate my 90% weed killer grade acetic acid to glacial for the
occasion. I think i will try this and report back, though, since the tetraethylhalide electrolytes yielded nothing at all, i wonder if maybe i need to
change out the bromide for something else?
Im not particularly comfortable with trying to synthesize thiocyanate, since there doesnt really seem to be a way around it without using cyanide, and
i dont understand its chemistry at all and see that it can potentially hydrolyze back to cyanide, and, if the cost is just efficiency or anode
lifespan, then i already have what i need right now.
now that being said, i also have a bit of a silly postulation, since potassium cyanate was shown to work, but not tested on graphite, just boron doped
diamond which performed universally worse than graphite. what if i stuck cyanate onto TBA? potassium cyanate performed terrible, but it did perform,
also these results were all from butyric anhydride formation not acetic, so idk how that translates, and if even the values are a yield cap since all
tests were done with 1.1F, not run all the way to determine where they top out, aside from a general statement that 70% is as high as it goes
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clearly_not_atara
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Ha, what an amazing method to end up on the end of a page. Nice find, Waffles.
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Waffles SS
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Thanks,
I also know better and more exciting method for synthesis Ac2O!
Do you have access to vinyl acetate or acetylene gas?are you ready for introduce another interesting method?(my favorite method )
Chemistry = Chem + is + Try
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chempyre235
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Not sure what country you live in, but Scientific Polymer has vinyl acetate for 8-10 cents/gram, depending on the quantity purchased.
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Waffles SS
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Here the price of VA monomer is 2$ per kg
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chempyre235
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Who sells it? If they're US, I might add to my list of suppliers.
"However beautiful the strategy, you should occasionally look at the results." -Winston Churchill
"I weep at the sight of flaming acetic anhydride." -@Madscientist
"...the elements shall melt with fervent heat..." -2 Peter 3:10
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Waffles SS
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My Vinyl acetate monomer made by Shazand Petrochemical Company
[Edited on 20-8-2025 by Waffles SS]
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MrDoctor
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i have noticed here and there occasionally its mentioned acetic anhydride decomposes when boiled/distilled, could someone elaborate on this? im
currently distilling an AcOH/Ac2O mixture of unknown concentration and its kind of stuck at 123-125C, afaik the acid content should be dropping it
shouldnt be forming a stable constant boiling mixture, but it does have me concerned its somehow decomposing.
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clearly_not_atara
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I think there are other ways to separate them, like by crystallization. You could chill and mix with a light alkane or similar np. AcOH will ppt.
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MrDoctor
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it looks like ill have to try that. i think i finally managed to prepare a modest quantity of pure acetic anhydride to deliberately dilute and test
the feasibility of seperation from the acid. as for the odd behaviour i noted earlier, i believe thats just because where the curves meet in the
middle, a certain mixture of acid/anhydride is favored so it hangs around 125C for a long time.
I really want to see if its possible to isolate the acetic anhydride from around 500ml of 20% anhydride in acid. its the upper end of what glutaric
anhydride will get, or pessimistically what sulfobenzoic anhydride (made from saccharine) will get, and similarly, the lower end of what electrolysis
with thiocyanate in acetonitrile will give.
While on the subject, i dont recall if i read this in literature or if grok spewed it to me, but is there perhaps a salt that can be used to brine-out
the anhydride? the one recommended to me was anhydrous magnesium chloride. it seems logical that if you had a salt soluble in acetic acid and
specifically NOT soluble in acetic anhydride, that some amount would cause layering to occur. Or similarly allow for efficient seperation of acetic
acid/anydride from toluene since the 3 are miscible and form a ternary azeotrope of sorts.
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Alkoholvergiftung
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Why do you have an acid mix? Did you use the thermal cracking methode of glacial acetic acid. coincidence i searched patents of acetic acid anhydrid
and i found some patents on cracking glacial acetic acid vaposrs on silica gel catalyst at 700C and they wrote an yield of 54% anhydrid and the rest
is glacial acetic acid. If used80% acetic acid temperature for the cracking is 750C and yield is only 48%. Also an mix with acetic acid. If you can
separet them without problems maybe an interesting methode of making AcO.
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bnull
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| Quote: Originally posted by clearly_not_atara | | I think there are other ways to separate them, like by crystallization. You could chill and mix with a light alkane or similar np. AcOH will ppt.
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This, I believe:
Attachment: US1941951.pdf (347kB)
This file has been downloaded 75 times
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Waffles SS
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| Quote: Originally posted by MrDoctor | it looks like ill have to try that. i think i finally managed to prepare a modest quantity of pure acetic anhydride to deliberately dilute and test
the feasibility of seperation from the acid. as for the odd behaviour i noted earlier, i believe thats just because where the curves meet in the
middle, a certain mixture of acid/anhydride is favored so it hangs around 125C for a long time.
I really want to see if its possible to isolate the acetic anhydride from around 500ml of 20% anhydride in acid. its the upper end of what glutaric
anhydride will get, or pessimistically what sulfobenzoic anhydride (made from saccharine) will get, and similarly, the lower end of what electrolysis
with thiocyanate in acetonitrile will give.
While on the subject, i dont recall if i read this in literature or if grok spewed it to me, but is there perhaps a salt that can be used to brine-out
the anhydride? the one recommended to me was anhydrous magnesium chloride. it seems logical that if you had a salt soluble in acetic acid and
specifically NOT soluble in acetic anhydride, that some amount would cause layering to occur. Or similarly allow for efficient seperation of acetic
acid/anydride from toluene since the 3 are miscible and form a ternary azeotrope of sorts.
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I was successful in separation of Ac2O from AcOH by fraction distallation but you should have good column and repeat it tree times at last but if you
can provide <-50c then separation will be easier(i reach this temp by homemade dry ice).
If you are serious in making AC2O i suggest Vinyl acetate route (or better isopropenyl acetate) that is easier and good yield method.
[Edited on 14-11-2025 by Waffles SS]
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MrDoctor
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| Quote: Originally posted by Waffles SS |
If you are serious in making AC2O i suggest Vinyl acetate route (or better isopropenyl acetate) that is easier and good yield method.
[Edited on 14-11-2025 by Waffles SS] |
How is that done? i tried searching it up but all i found was you saying you tried a certain reaction and it didnt work. Or did you mean indirectly
using it as an acetaldehyde source?
Ultimately i wound up getting some pure acetic anhydride but im curious as to what method could be used.
also turns out what i was distilling in the 120s was just a contaminant, distilling these mixtures seems not too unlike distilling ethanol and is
vastly simpler to make pure if the starting conc is high, so instead im just going to test out some methods of salt/brining the anhydride out, one
thing i never considered either was the possibility of just saturating the acid with glutaric anhydride and seeing what happens when i have a known
quantity of anhydride present, and not presumed based on a patent.
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Waffles SS
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| Quote: Originally posted by MrDoctor |
How is that done? i tried searching it up but all i found was you saying you tried a certain reaction and it didnt work. Or did you mean indirectly
using it as an acetaldehyde source?
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VA +ACOH -catalyst->acetaldehyde +Ac2O
Search this topic .(i posted details before.)
| Quote: |
Example 7
In a copper kettle with an attached fractionation column, a mixture of 860 parts vinyl acetate, 600 parts acetic acid, 1.0 part sulfuric acid, and 2.0
parts phosphoric acid was boiled. The resulting aldehyde was distilled off in a nitrogen stream of 20 volume units per hour. The distillation of the
aldehyde proceeded more smoothly than without a gas stream. The residue remaining in the kettle contained 75% acetic anhydride, which, during
fractionation under vacuum, was largely obtained directly as a 98% pure product. The material yield was almost quantitative. The resin produced
amounted to only 0.37% of the feedstock.
DE503131
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Attachment: DE503131C.pdf (244kB)
This file has been downloaded 58 times
This is my setup for this reaction and separation(there are glass marble in column )
[Edited on 14-11-2025 by Waffles SS]
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Radiums Lab
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Ketene can be prepared by heting CH3COOH in Fe tubes. I know ketene is toxic but...
Water is dangerous if you don't know how to handle it, elemental fluorine (F₂) on the other hand is pretty tame if you know what you are doing.
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Alkoholvergiftung
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waffle ss i ve found an swiss patent where they use acetaldehyd and glacial acetic acid whith an cobalt or copperacetat catalyst. It forms acetic
anhydride too. Maybe so you can use your acetaldehyd waste. 
Attachment: AcO.Acetaldehyd_all_pages.pdf (140kB)
This file has been downloaded 59 times
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Waffles SS
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| Quote: Originally posted by Alkoholvergiftung | | waffle ss i ve found an swiss patent where they use acetaldehyd and glacial acetic acid whith an cobalt or copperacetat catalyst. It forms acetic
anhydride too. Maybe so you can use your acetaldehyd waste.
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Acetic anhydride from acetaldehyde and cobalt catalyst mentioned before in this topic.
This method is not feasible and need special equipment that is not available for most of amateur chemists.
There are interesting methods for synthesis acetic anhydride, but this method is not one of them.
Do you want I introduce one of that interesting method?
[Edited on 14-11-2025 by Waffles SS]
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Alkoholvergiftung
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Yes Sensei, teach. Only found the direct methode of 8mol of Sodiumacetat 1
mol sulfur and than chlorine. So no sulfurdichloride must be made.
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Waffles SS
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One of easiest and fastest method for synthesis Ac2O is Dehydrating AcOH by DCC(N,N'-Dicyclohexylcarbodiimide)
Add acetic acid to same volume of dichloromethane and then add calculated amount of DCC,Stir for 30 minutes at 30-40c filter insoluble material and
evaporate solvent and done,You will get good yield of Ac2O.
DCC is available in most of organic lab and i think is not illegal in your country (but careful about toxicity )
[Edited on 14-11-2025 by Waffles SS]
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MaeBorowski
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Two old Soviet patents claim that AA can be made from acetamide, acetic acid, and a strong acid (H2SO4 or HCl in these cases).
SU17216: 2AcNH2 + 2AcOH + H2SO4 = 2Ac2O + (NH4)2SO4
A mixture of acetic acid, acetamide, and sulfuric acid taken in the corresponding ratio (2:2:1 moles) is heated in a flask, and the forming AA is
distilled off with a Vigreux column. The distillate is purified by fractional distillation, yielding a product containing 85 to 93% of AA (that's not
the yield!!).
SU19625: AcNH2 + AcOH + HCl = Ac2O + NH4Cl
Hydrogen chloride is passed into a mixture of acetamide and glacial acetic acid (1:1 moles). The formed acetic anhydride is distilled with a Vigreux
column. The fraction boiling between 130 and 142 C is redistilled, giving a product with up to 96% AA (again, it's not the yield. the patent doesn't
say anything about the temperature that should be maintained during the saturation, but it could get pretty hot without external cooling)
What has been will be again, what has been done will be done again; there is nothing new under the sun. Eccl. 1:9
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Waffles SS
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| Quote: Originally posted by MaeBorowski | Two old Soviet patents claim that AA can be made from acetamide, acetic acid, and a strong acid (H2SO4 or HCl in these cases).
SU17216: 2AcNH2 + 2AcOH + H2SO4 = 2Ac2O + (NH4)2SO4
A mixture of acetic acid, acetamide, and sulfuric acid taken in the corresponding ratio (2:2:1 moles) is heated in a flask, and the forming AA is
distilled off with a Vigreux column. The distillate is purified by fractional distillation, yielding a product containing 85 to 93% of AA (that's not
the yield!!).
SU19625: AcNH2 + AcOH + HCl = Ac2O + NH4Cl
Hydrogen chloride is passed into a mixture of acetamide and glacial acetic acid (1:1 moles). The formed acetic anhydride is distilled with a Vigreux
column. The fraction boiling between 130 and 142 C is redistilled, giving a product with up to 96% AA (again, it's not the yield. the patent doesn't
say anything about the temperature that should be maintained during the saturation, but it could get pretty hot without external cooling)
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Many years ago i tried this method and i have to say another bullshit method.
dont waste your time and money !
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MaeBorowski
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It appeared quite obscure and hadn't been mentioned here, or at least I wasn't able to find any methods involving acetamide  Sorry for relaying false data.
Do you remember any details of your experiments?
What has been will be again, what has been done will be done again; there is nothing new under the sun. Eccl. 1:9
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Waffles SS
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I did this experiment 10 years ago and i dont remember details.but i remember this patent was/is bullshit.
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Alkoholvergiftung
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Waffles. Could Polyvinylacetat also be used? It is sold as Glue it could be bought in 5l containers.
[Edited on 28-12-2025 by Alkoholvergiftung]
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