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Author: Subject: Acetic anhydride preparation
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[*] posted on 7-5-2005 at 04:37


Relevant part of the second patent:

Crystalline sodium thiosulfate is made anhydrous by heating and then pulverized. 185 parts of this are mixed with 820 parts pulverised, anhydrous sodium acetate.
This mixture is reacted with chlorine at 40- 50°C. The chlorine addition is stopped when no more is absorbed. Approx. 285 parts are needed. Too much chlorine decreases the yield and the purity of the final product by chlorination of the carbon chain.
A high vacuum is applied to the reaction chamber and it is heated with pressurized steam of 7 bar pressure from the outside (oil bath should also work).
The acetic anhydride distills off.
With correct procedure, about 460 parts acetic anhydride are obtained (a 90% yield). A good yield is only obtained when water in any form is excluded from the reaction.


[Edited on 7-5-2005 by garage chemist]
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Mahlzahn
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[*] posted on 7-5-2005 at 06:45


Of interest are for instance the incursion:

4CH3COOH + 4NaBr ;) -->
4CH3COOBr + 4Na + 2H + 2e + H2

4CH3COOBr + O2 catalyst -->
2(CH3-CO)2O + 2Br2O

:o
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kmno4
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[*] posted on 1-6-2005 at 14:18


Quote:
Originally posted by CD-ROM-LAUFWERK
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)

I tried to do the same , but effects was strange...
First, I prepared 218g AcOH(wet) and 76g P2O5. I placed P2O5 in distillation flask eqiped with vertical condenser and added about 20cm3 AcOH through it. In ten seconds it started to get brown, then blac and I saw a little white fumes inside flask. I added the rest of acid in 1/2 hour, temperature inside reached about 80C.
The mixture was deep brown, almost black, but I tried to distill this. I collected about 160g liquid between 118-121C. I was afraid to colect more, because the residue in flask was looking like boiling tar. So I recovered 160g of pure acetic acid:( I took this acid, placed it in a bottle, and slowly added 46g P2O5 in portions. First portion added and... nothing happens !! Another one - still nothing.
After adding this 46g nothing special has happened. No heat, no traces of any reaction*. Then I tried to calculate heat of such reaction:
12AcOH+P4O10->4H3PO4+6Ac2O
Enthalpy(dH) this reaction is:+18kJ - not exothemic!
dG is:+38kJ - not possible:P:P!
Conclusions ?
At first time, wet(97%) AA was dried by P2O5, in small volume there was great evolving of heat and this caused exothermic charring of AA...
Propably H3PO4 is not formating in this reaction, maybe HPO3 and other phosphorus acids are. There must be used much more than 35gP2O5 per 100gAA to conver it (quantitiv)in Ac2O, at least I think so.
*in a bottle P2O5 started to get yellow(why?) and slowly disappears. I am wondering if it all is worth my job(P2O5 is cheap, about 10 dollars per 1kg:D)
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[*] posted on 2-6-2005 at 05:43


Quote:
I tried to do the same , but effects was strange...
First, I prepared 218g AcOH(wet) and 76g P2O5. I placed P2O5 in distillation flask eqiped with vertical condenser and added about 20cm3 AcOH through it. In ten seconds it started to get brown, then blac and I saw a little white fumes inside flask. I added the rest of acid in 1/2 hour, temperature inside reached about 80C.
The mixture was deep brown, almost black, but I tried to distill this. I collected about 160g liquid between 118-121C. I was afraid to colect more, because the residue in flask was looking like boiling tar. So I recovered 160g of pure acetic acid I took this acid, placed it in a bottle, and slowly added 46g P2O5 in portions. First portion added and... nothing happens !! Another one - still nothing.
After adding this 46g nothing special has happened. No heat, no traces of any reaction*.

u added the acetic acid to the P2O5????
ther must be keten formed, the anhydrid from acetic anhydrid (its a gas)
i dont think that u used clean P2O5 :P
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[*] posted on 2-6-2005 at 09:21


My preferred production method for Ac2O would be the production of acetyl chloride from benzalchloride or benzotrichloride (from toluene + chlorine) and acetic acid (ZnCl2 catalyst is required), then reaction of the acetyl chloride with sodium acetate.

Or you could directly use the acetyl chloride in place of acetic anhydride, they are both powerful acetylating agents.
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[*] posted on 2-6-2005 at 10:38


Has anyone tested the method in US1926087?

2NaPO3 + 4CH3COOH -> 2NaH2PO4 + 2(CH3CO)2O

That seems just too easy. Distill off the anhydride (or filter, then distill), possibly with a column, and heat the orthophosphate to +300C (?) for few hours to convert it back to the metaphosphate.
This really should be tested IMO.
Phosphates and acetic acid are both OTC in their pure forms.

EDIT:
Ok, this seems to be similar to the experiments kmno4 and CD-ROM-LAUFWERK did. Maybe using a phosphate salt doesn't dehydrate it so strongly as P2O5 does and results in a purer product?
Sodium orthophosphate decomposes to pyrophosphate at 240C according to Patnaik.
Haven't found any other info on pyrophosphate than the MSDS, which just said that it decomposes to sodium and phosphorus oxides on heating.
I'll try to make some sodium metaphosphate from phosphoric acid and sodium carbonate tomorrow.

[Edited on 2.6.2005 by IPN]

[Edited on 2.6.2005 by IPN]
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[*] posted on 4-6-2005 at 09:06
ketene lamp


I still don't understand why the ketene lamp method is so unpopular. Vogel has a rather descriptive diagram of the setup and explaination on page 373. If it could be done in 1948, it shouldn't be that hard to repeat.

Obviously there is the toxicity to deal with, but this is not so bad since ketene is supposed to have a characteristic odor (anyone know what it smells like?) The other problem is just how reactive/corrosive ketene is to various types of tubing. Vogel's device is made entirely from pyrex glass, but why couldn't say copper tubing be used? The electrical connections for the NiChrome grid he uses is supported by platinum, nickel, and brass terminals which would be directly exposed to the newly formed ketene.

Due to the reactivity of ketene towards organic materials, I could see that most plastics are probably unsuitable, but what about PTFE plastic? Anyways, I also dont see the need for two condensors as Vogel's setup has either. All one would really need is a very effecient condenser in a reflux configuration to recondense the unreacted acetone, while the newly formed ketene and other gas byproducts would flow out of the reactor.

I do not feel the need to so quickly discount this method. After all, once the equipment is dealt with, acetone is very cheap, and even if 30% molar yeilds are realized (conservative estimate from Orgsyn) one could obtain 15g of AA from 58g acetone without that much work (aside fromt the equipment setup again).

I'd really like to know more about what materials ketene is compatable with and what it will degrade (specifically plastics).
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[*] posted on 4-6-2005 at 10:24


On the topic of ketene lamps, what would happen if you used MEK in a ketene lamp instead of acetone. Would you get methyl-ketene?
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[*] posted on 6-6-2005 at 09:41


I neutralized 50ml of phosphoric acid with sodium carbonate and heated the viscous paste in a steel crucible over a propane burner for few hours. I should now have at least sodium pyrophosphate.
According to the Handbook of Preparative Inorganic Chemistry, metaphosphate requires temperatures over 1000C. Can this be correct? If so then this doesn't seem that good method after all..
Maybe it would work with just the pyrophosphate?
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[*] posted on 26-8-2005 at 05:17
Acetic Anhydride


Hi, I just like to know why all that interest in making AA. I think organic chemistry has a lot more interesting subjects than this one...

Regards,
Alfredo
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[*] posted on 26-8-2005 at 15:57


This answer applies to just about every synthesis on this board: it's a useful chemical that can't be easily bought.
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[*] posted on 26-8-2005 at 21:40


Also it is laughing in the face of the powers that be, they do not want us to have it as it is an 'evil chemical' with potentially illegal uses, when we just want it for regular chemisty.



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wink.gif posted on 29-8-2005 at 09:13
Ketene lamp


Ok, if you want to make AA, why not? I think the easy way is using a ketene lamp. I´m going to build one here since I have a research project were I will use ketene. I´m building the Vogel´s equipment and I´m going to use polypropilene tubes. I think they should resist very well to ketene. Anyway, as long as I start the ketene production I will put a photo and tell if PP tubes are resistant enough.
Alfredo:cool:
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[*] posted on 4-9-2005 at 14:35


Preparation of Acetic Anhydride from AcOH and my new favourite water scavenger (HPO3)n has been unsuccessful.

The same as with P2O5 happens: there is a reaction and heat is evolved, but you just distill off pure acetic acid and the residue is boiling tar.

Preparation of Acetic Anhydride from AcOH and a water scavenging agent is NOT POSSIBLE.
Formation of a carboxylic anhydride is a VERY DIFFERENT reaction than formation of the anhydride of a mineral acid.
It cannot be effected by water scavengers. Different methods must be employed to form the CO-O-CO (carboxylic anhydride) group.
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[*] posted on 8-9-2005 at 15:44


I think SO3 has been used for the purpose. Funny that it doesn't work, but interesting nevertheless.
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[*] posted on 14-10-2005 at 12:48


An addendum to the translation of garage chemist, at the top of the page:

water vapor at 7atmospheres is approx. 165°C hot.

I think after all, the thiosulfate-patent should be simple enough to try. (the ketene-lamp seems simple, but can i really operate a ketene lamp in a small room with only a small window for ventilation?:( )

[Edited on 15-10-2005 by BASF]




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[*] posted on 18-10-2005 at 12:15


Hmm I dont really trust that can S2Cl2 can be used to make acetyl chloride. All the textbook procedures make use of PCl3.

[Edited on 20-10-2005 by Illegal Parkinson]
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biggrin.gif posted on 22-10-2005 at 12:09
Just a further undiscovered method..


The preparation of acetic anhydride by the action of nitrogen peroxide on sodium acetate. Rodionov, V. M.; Oblitseva, T. A. Trudy VI Vsesoyuz. Mendeleev. S'ezda Teoret. i Priklad. Chim. 2(No. 1), 1002-3. From: Chem. Zentr. 1938, II, 4054. Journal language unavailable. CAN 34:43152 AN 1940:43152 CAPLUS

Abstract

R. and Smarin found that when N2O4 was passed over dry NaOAc, Ac2O was formed. The reaction is 2AcONa + 2N2O4 = Ac2O + 2NaNO3 + N2O3. The N2O3 does not act on the NaOAc. Formation of Ac2O takes place also in mixts. with air but the yield is smaller than with the pure N2O4. The Ac2O yield is 85%. The N2O4 was prepd. either by strongly heating Pb (NO3)2 or from nitrosylsulfuric acid and NaNO3 according to the equation: HOSO2ONO + NaNO3 = NaOSO2OH + N2O4. The action of N2O4 on the salts of other fatty acids was investigated and good yields of propionic and butyric anhydrides were obtained. Somewhat poorer yields were obtained in the prepn. of the anhydrides of isovaleric and stearic acids.
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[*] posted on 22-10-2005 at 13:24
What the?


So, I wonder what keeps the N2O4 or byproduct N2O3 from deteriating the Ac2O? Is this done at room temperature?

[Edited on 10/22/2005 by chloric1]




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[*] posted on 22-10-2005 at 13:59


Cool method:) Literally...
In order for the N2O4<->2NO2 equilibrium to lie to the left, the N2O4 side, this reaction would likely have to take place at a sugnificantly lower than room temp.



[Edited on 22-10-2005 by rogue chemist]




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[*] posted on 27-11-2005 at 19:17
acetic anhydride


You can try distilling a mixture of Anhydrous sodium acetate and acetyl chloride.Yields is fairly good.You have to add acetyl chl;oride drop wise to sodium acetate .The distilled crude iquid has to be redistilled to get pure product.
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[*] posted on 27-11-2005 at 19:44


I'm going to assume that this was overlooked, otherwise I don't see why there'd be a continuing discussion on this.

Acetic Anhydride and Propionic Anhydride
Drone #342:

Here's what everyone's looking for. Some things are a little wierd about it, like the fact in the acetic anhydride synth they use a small quantity of acetic anhydride as a solvent. However, as one sees in propionic anhydride, such a solvent may not be necessary.

From "Chemistry & Industry", 1945, p. 382; "LABORATORY METHOD FOR THE PREPARATION OF ORGANIC ACID ANHYDRIDES" by Jehuda Orshansky and Eliahu Bograchov.

"...(1) Acetic anhydride. To 50 g. acetic anhydride in a round-bottomed flask of 1500 cc. capacity, placed in cold water, 440 g. of powdered sodium acetate (dried by fusion at 320 C) and at the same time a solution of 22. g of sulfur in 320 g. bromine is added while stirring. The operation takes about 30 minutes.

"The mixture is then stirred for a further 5 minutes, after which period the initially dark brownish-red colour has changed into pale yellow, and the anhydride is distilled off from a water bath under reduced pressure. The crude anhydrie (310 g) is redistilled under normal pressure, and the fraction boiling between 134-138 C is collected. Yield, 295 g. of 98% purity = 87.5%. The so purified anhydride contains neither bromine nor sulphur compounds and leaves no residue on evaporation..."

"(2) Propionic anhydride. To 40 g. fused and powdered sodium propionate in a flask of 250 cc. capacity a solution of 2 g. sulphur in 22 g. bromine was added while stirring. The temperature was kept at about 50 C. When the operation was completed, the anhydride was distilled off in vacuo. The crude product (25g.) was fractioned under normal pressure, and the fraction 155-156 C was collected. Yield, 23 g. propionic anhdride of 90% purity = 85%..."

The paper mentions that other alkali metals and alkali earth metals work just fine. Calcium propionate is a food preservative added to cheap white bread to keep it from molding. With these nuggets of information, the most closely watched reagent on the DEA's watched list, propionic anhydride, just turned OTC. I can almost see the fentanyl analogs clogging the opioid market already.

The one reason, and justafiably so, they poo-poo using chlorine (which does indeed work nicely) is that its a hassle to work with, especially considering the fact that they'd be adding a gas to a solid to make a liquid. I propose that perhaps with the use of chloroform as a solvent, chlorine could be bubbled in readily, and the reaction would go as previously stated. I assume they tried to avoid using extra solvents in hopes of staying away from azeotropes messing up their products' purity, so this may or may not work, depending on what you're trying to do.

Iudexk:

To 66.5g fused AcONa (made from AcOH + NaOH) was added a soln. of 3.3g S in 48.4g Br2 over 5mins, under manual stirring. Brown colour disappears rapidly on stirring to give slightly off-white mixture. Stirring continued for another 15mins. Mixture has v. strange consistancy; becomes almost liquid while stirring but as soon as one stops stirring it becomes solid again. Thus formed sludge was scooped up and dumped in a distillation flask (spilling much in the process - do this rxn in the same flask you're gonna distil from), and distilled.

Yield of Ac2O = 29.2g as a clear pungent liquid.

Note that basically all you need is NaOAc, S, and Br2. And some distilling equipment.
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[*] posted on 28-11-2005 at 11:36


:mad:

I don´t want to discourage you after finding this "unknown" method....
but,
1) the first method uses Ac2O as a solvent. It´s always nice if you need the target compound when you attempt to make the target compound...
2)Bromine is not exactly OTC, nor is it cheap or anything else. -Agreed?

Please no more acetylchloride/bromine - methods!

[Edited on 28-11-2005 by BASF]
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[*] posted on 28-11-2005 at 14:09


As soon as you get a kilogram of a bromide salt (CaBr2*H2O in my case, it is sold for making high-density drilling fluids, a saturated CaBr2 solution has got a density of 1,64 g/ml) and adapted the process of bromine production according to your ressources (like what oxidiser you use: I use NaClO3, but H2O2, MnO2, Cl2 and others just work as well) you will find bromine to be a cheap chemical.
Also, the bromine can be fully regenerated from the residues of Ac2O production, it is present in the form of bromide there which just needs to be treated with acid and an oxidiser.

But the N2O4/NaAc process is most interesting, if it works it has got enormous potential.
Let's discuss methods of NO2/N2O4 production. Heating of lead nitrate might be the method of choice for research labs, but for us lead nitrate is too expensive and difficult to make.
Heating calcium nitrate might be a better idea, as this is easier to get (fertilizer).
But this is the tetrahydrate, dehydrating the salt using heat is really messy, I've tried it.

Any more ideas for convenient and controllable production of dry NO2/N2O4?

[Edited on 28-11-2005 by garage chemist]
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[*] posted on 28-11-2005 at 14:20


Quote:
Originally posted by BASF
:mad:

I don´t want to discourage you after finding this "unknown" method....
but,
1) the first method uses Ac2O as a solvent. It´s always nice if you need the target compound when you attempt to make the target compound...
2)Bromine is not exactly OTC, nor is it cheap or anything else. -Agreed?

Please no more acetylchloride/bromine - methods!

[Edited on 28-11-2005 by BASF]


1) I can't say for sure but it does say that the anhydride as a solvent "may NOT be needed"

2) Actually, bromine IS "exactly OTC". Go to a pool supply store, buy sodium bromide, sodium bisulfate, and potassium persulfate. All your ingredients right there in one shot. Or you could get a cheap gallon of HCl at a hardware store for $5, and use an oxidizer that may be more convenient.
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