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Author: Subject: Acetic anhydride preparation
Marvin
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[*] posted on 30-4-2004 at 14:06


Umm more economical pyrosulphate methods!

What about,

Na2SO4 + H2SO4 => 2NaHSO4

Then at 300C or so as mentioned,

2NaHSO4 => Na2S2O7 + H2O.


Nice tip btw, Hjalmar, method for AA is completely new to me.
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BASF
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[*] posted on 3-5-2004 at 08:28


"What about,

Na2SO4 + H2SO4 => 2NaHSO4

Then at 300C or so as mentioned,

2NaHSO4 => Na2S2O7 + H2O. "

Rather 400°C than 300°C, no?

Heating also costs money. I like the method for Na2S2O7 using SO2-gas because it does not involve such excessive heating.

...although I have nothing at all against simplicity :P

[Edited on 3-5-2004 by BASF]
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Hjalmar_Poelzig
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[*] posted on 3-5-2004 at 08:55
the patent


It is in US patent 1430304

Also, I seem to remember that it is not possible to get a quantitative yield of the pyrosulfate, as at some point SO3 will start to form.

But considering the cheapness and easy availability of the reagents this should not be much a problem.

EDIT:
Your method using KOH, CuCl2 and SO2 in IPA seems *very* nice to me, BASF, thanks! :D

[Edited on 3-5-2004 by Hjalmar_Poelzig]
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frogfot
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[*] posted on 11-5-2004 at 13:38


Problem with NaHSO4 decomp is that Na2S2O7 decomposes to SO3 and Na2SO4 at 460*C. Although temp diffeence is about 100 degrees, it may be hard to control with just a gas burner..
But still, not like I have any cheap SO2 to go with the other route, this is worth to test.

Acetate + CO2 method sounds to good to be true.. :o If this really gives good results, I know where to apply CO2 from next (theoretical) wash batch :P (ofcaurse a big gas drying column should be made..)
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frogfot
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[*] posted on 16-7-2004 at 07:09


KHSO4 dehydration seems to work very nicely. I've heated some, it melted and started to boil vigorously. After, boiling slowed down to almost zero, there appeared white fumes. So everything seems to go as planned. (Btw, OT, how about this one as an SO3 source)

I then broke solid pyrosulfate to small pieces, mixed with about 1,6 parts dry sodium acetate and 100 ml ethyl acetate. Stuff has refluxed now for about 0,5h (and counting..) with a CaCl2 drying tube and pyrosulfate chunks seem to dissapear/react.. While reaction mix becomes a bit more mobile.

Is ethyl acetate a good choice of a solvent? It shouldn't consume any acetic anhydride.. or?
In the end of reaction I wanna filter off solid K2SO4, evap solvent to hopefully recover AA anhydride..

EDIT:
Duh, ethyl acetate didn't do a squat.. however I've added some dry acetic acid to the pyrosulfate/acetate, and it heated alot! Nice to know that something is happening :)

[Edited on 16-7-2004 by frogfot]

[Edited on 16-7-2004 by frogfot]
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Theoretic
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[*] posted on 1-10-2004 at 10:55


What about Ca(CH3COO)2 + NH4HCO3? Partial hydrolysis of HCO3- should give CO2 in a dissolved state, ammonium carbonate shouldn't be alkaline enough to cause rapid hydrolysis of Ac2O, while CaCO3 should precipitate and thus facilitate the reaction. I think this is better than the NaCH3COO + CO2 method.

A better method for quickly forcing the pyrosulfate route is dropping all your acetate into the molten pyrosulfate and condensing the fumes, the anhydryde might be affected by hot pyrosulfate or heat generally.




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neutrino
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[*] posted on 1-10-2004 at 13:30


What I don't understand is why only salts of acetic acid work in the pyrosulfate method and not the acid itself. The acid is, after all, the hydrogen salt. Pyrosulfates will dehydrate sulfuric acid to its anhydride, so why not acetic?
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[*] posted on 16-2-2005 at 04:05
Acetic anhydride- it's really that easy!


Acetic anhydride from sodium acetate, using S2Cl2

Translated from russian by Antoncho

Prepare 100g freshly fused NaOAc and 65g S2Cl2. A small quantity of NaOAc is placed in a thin-walled glass cooled in an ice bath. To this is added some sulfur chloride, the mixtr is vigorously stirred w/a wooden spatula, not allowing the temp to rise. Then some NaOAc is added again, and the process is repeated several times until all is mixed in. The semi-liquid mass is transferred into a 1 liter RBF. The previous operation is repeated 4 times, so that 400g NaOAc and 260 g S2Cl2 total are taken into work. The RBF is then equipped w/a reflux condenser and gently heated on a water bath to ~80-85°C. As soon as the rxn starts, the heating is removed, and in case the rxn gets too vigorous it's cooled w/cold water. After 20-30 min SO2 evolution ceases and the mixture is heated for 10 more min's on a boiling water bath. The rxn product is then distilled off under vacuum, then fractionally re-distilled at ordinary pressure, collecting the fraction boiling between 132-142°C.

For further purification it's distilled with 2-3% KMnO4 or K2Cr2O7 for breakage of sulfurous contaminants (test for their presence: 1 ml of the distillate upon neutralization w/pure NH3 mustn't give a dark precipitate on treatment with Pb(AcO)2) The yield is ~90% based on S2Cl2.

(From Rhodium's site)


I am surprised that nobody here works with sulfur chlorides. They are easy to make!
As I wanted to tell everyone in the "disulfur dichloride" thread, you can produce S2Cl2 by the liter when you have a ground- glass still.
Sulfur and chlorine are most easy to get.
Just insert a gas inlet tube into the thermometer adapter down into the boiling flask, exactly as you would do with a boiling capillary for vacuum distillation.
The chlorine doesn't even have to be dry!

I have 20ml of S2Cl2 sitting around, I only didn't make more because I didn't know of its usefulness to produce acetic anhydride until now.
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[*] posted on 16-2-2005 at 05:46


On this thread somewhere were stated the half-lives of acetic anhydride at different temperatures. At rtp what is the half life of acetic anhydride? Could it be possibly as low as stated previously (a few minutes IIRC!!!)? At what temperature should it be preferably stored then to slow down this decomposition, and at such temp. what would be the half life?

I have searched around the net but found not references to the half life ot ethanoic anhydride. Any information about it's half life would be awesome! Thanks.




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[*] posted on 16-2-2005 at 06:38


We use litres of acetic anhydride for peptide synthesis, and the stuff is kept in a normal glass bottle in the dark, for months/years. I don't think it decomposes, because else it'd 1) say on the bottle, and 2) be useless for the synthesis.

Hangon - halflife - to what is it supposed to decay to?




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Esplosivo
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[*] posted on 16-2-2005 at 08:51


Right now I noticed that I had a mistake, Hermes was refering to the 'half-life' of acetic anhydride in water. I still don't like the term half-life though, but it makes more sense like that.

Thank you for your help, since at least now I know that acetic anhydride 'does not' decompose on storage.




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[*] posted on 16-2-2005 at 12:48


I've read that the downside of using sulfur chlorides as reagents is that the reaction products often have sulfur compounds as contamination. This is the case with preparation of ethylene chlorohydrin from ethylene glycol with S2Cl2, for example. This is not to say that the method is useless, but in some cases it is going to give trouble. One notorious example is hydrogenation catalyst poisoning.
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[*] posted on 23-2-2005 at 12:14


Would passing acetone (propanone) vapour through a thin (approx 5mm in diameter) copper tube heated with 4 bunsen burners of the LP type (fueled with butane/natural gas) be enough for the pyrolysis of acetone to ketene to occur? I am very interested in such a method of production, and will probably try it out next summer. Thanks for the help.



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alchemie
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[*] posted on 23-2-2005 at 13:24


Quote:
Originally posted by Esplosivo
Right now I noticed that I had a mistake, Hermes was refering to the 'half-life' of acetic anhydride in water. I still don't like the term half-life though, but it makes more sense like that.



I'm sure what is meant is: "the half-life of the reaction of acetic anhydride with water".

The half-life of a reaction is just the amount of time that it takes for the consumption of half of the limiting reactant.

The confusion here is with the decai of radiactive nuclei, where "half-life" is the time necessary for the half of the original nuclei to decay.
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[*] posted on 10-3-2005 at 19:51
anhydrides


hi hoffman i persume you want the anhydride for p2p production
i have used it before its not fun
as far as for making it tou will need a distillation of your anhydride
I WOULD NOT LIKE TO BE AROUND FOR THAT there is betta way to use phenylacetic acid after the making of p2p you have to disstill down the anhydride not fun
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S.C. Wack
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[*] posted on 10-3-2005 at 20:57


Hermes never reported back. The best patent wasn't mentioned, GB486964, an addendum to Consalvo's other patent, the aforementioned GB480953. (There are also FR versions of these two, FR47873E and the earlier FR809731)
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SAM4CH
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[*] posted on 24-3-2005 at 10:43
Acetic anhydride from acetate


Can I get acetic anhydride from molten sodium acetate by reaction with Cl2 gas?!
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[*] posted on 4-5-2005 at 16:55


Sorry to bring this topic up again, but an alternative route is described, where an alkali salt of acetic acid is not used, just plain ol' KNO3:
Quote:

Acetyl Chloride (40gms) is mixed with KNO3 (7gms) in a flask attached to an upright condenser, which is closed by a calcium chloride tube.
A vigorous reaction is accompanied by the evolution of chlorine and nitrosyl chloride, and after standing for half an hour, the mixture is heated on a waterbath and gradually raised to boiling temperature, at which it is maintained for two hours. The colourless liquid mass is the extracted with ether to remove the KCl, and the ethereal extract fractionally distilled.
Yield 15-20gms; bp., 138°C


Ref. The synthetic use of metals in organic chemistry by Arthur J. Hale p. 125
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[*] posted on 4-5-2005 at 17:04


Too bad acetyl chloride is just as hard/harder to get than the acetic anhydride :(. most methods I have seen involve the use of phosphorous or obscure reageants.

Very interesting if you do have access to the compund though.




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neutrino
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[*] posted on 4-5-2005 at 17:07


We're trying to make this stuff from readily available chemicals, not exotic ones like acetyl chloride.
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[*] posted on 4-5-2005 at 17:18


Indeed you are right Painkilla (edit: and neutrino), but luckily, not all countries has banned phosphorous from the surface of earth, thus the route via PCl3 seems a little "easier" to come by.

[Edited on 5-5-2005 by Phel]
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[*] posted on 5-5-2005 at 06:34


Is it easy prepare acetic anhydride from
CH3COOH and the method correct ?
First buy some dilute vingar in a food store and than the vingar is concetrated by distillation (<118 gegree celsius) to concetrated CH3COOH.
(first the water is boiled out).

The oxidation (dehydration) of CH3COOH
with a homemade desillation equipment
are difficultly.
(Desillation bridge with a electrolytic catalyst-grid)

Examble: ;)
4CH3COOH + O2 [catalyst] -->
2(CH3-CO)2O + 2H2O

Other methods walking fine too.



[Edited on 5-5-2005 by Mahlzahn]
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S.C. Wack
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[*] posted on 5-5-2005 at 23:57


I don't remember seeing these anywhere before, so here are some interesting variations on known routes.

US1926087 is unusually detailed for a Dreyfus patent. Sodium metaphosphate and acetate are used here.

DE283163 uses chlorine and acetate as usual, but more conveniently uses thiosulfate instead of S or SO2.
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[*] posted on 6-5-2005 at 00:17


The first one is surely a very interesting patent, the second I can't read because its in german. Can anyone at least give a quick translation of the most relevant part - shouldn't take more than a couple of minutes for a german speaking guy right? Please.... Thanks.



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[*] posted on 7-5-2005 at 04:09


i slowly mixed 35g P2O5 to 100g of acetic acid (under a strange reaktion, much heat)
i think that over 95% of the acetic acid reacted to the anhydrid, after destillation the stuff dont frezze at temperaturs around -20°C!
per 2 mol. of P2O5 u can use 16 mol. of acetic acid, that will give u 8 mol. acetic anhydrid (per 30g P2O5 use 100g acetic acid)
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