Sciencemadness Discussion Board

Acetic anhydride, the 2nd.

BASF - 1-4-2003 at 09:51

I suggest trying a comparatively easy method to produce a mix of acetic anhydride and acetic acid:

For this method, i dared to presume that considerable amounts of acetic anhydride may be formed when mixing oleum(60% oleum, for instance) with glacial acetic acid.

Mix a big excess of fuming sulfuric acid with glacial acetic acid.
A mixture of acetic anhydride and acetic acid/oleum results.

I would then propose distilling off the rests of SO3 at moderate temperature(can be recycled by dissolving in conc. H2SO4), followed by distilling off as much of the lower boiling acetic acid as possible and then the last fraction should yield an azeotropic mix of acetic anhydride and acetic acid, which is far from being pure acetic anhydride i presume, but i´m sure it could be used in most nitrations where acetic acid is added to the anhydride anyway.

Also, considering acetic anhydride has a MP of
-73°C and acetic acid +17°C, a good effect of seperation may be achieved by freezing out acetic acid...

(BP acetic anhydride: 139°C; acetic acid: 118°C; BP SO3: 45°C; BP H2SO4: 338°C)


[Edited on 2-4-2003 by BASF]

Organikum - 1-4-2003 at 11:18

Bubbling SO3 in the GAA will be better. SO3 by boiling oleum and venting the fumes into the GAA.
There was another way to produce SO3 as oleum is not my all day acid, - have to look it up.

A usual laboratory device in former days was the "ketenelamp" for thermal decomposition of acetone to yield ketene which gives acetic anhydride if vented in GAA.
Enough on this dangerous industrial process, back to oleum and SO3 (H2S?).

I for my part would prefer making cyanides by Polverones way a thousand times before using oleum/SO3. But thats probably depending on personal taste and style.

BASF - 1-4-2003 at 11:55

Yeah, you probably mean the pyrolysis of sodium hydrogensulfate, cause this what i´ve also thought of.

I am aware of all these known methods using acetylchloride+sodium acetate, and the ketene-process, for instance, but the two are nasty.
One is made using a controlled substance(PCl3), if not a controlled substance itself, the other is with a gas of a toxicity in the magnitude of phosgene.
The third method i can immediately remember would be using P2O5 for dehydration, which is obviously also ridiculously insuitable for the hobby chemist.

Another attempt:

The Beilstein-Database spit out the following interesting reaction:

Pb(CH3COO)2 +CS2 ---> (165°C) acetic anhydride

I´m only wondering if this is a process to be performed at atmosperic pressure.


[Edited on 1-4-2003 by BASF]

Organikum - 1-4-2003 at 13:20

No, I actually spoke of:

ketene prepararion - Org.Synt.

You may also look in Vogels 3rd edition for this where procedure and apparatus is described in detail.

For those who prefer tubes over sophisticated glassware as I following patents are interesting:

US1723724 to Kodak
US2080562 coke and carbon tubes
US2108829 with excellent drawings
GB425973 the best adaptable in my eyes
US1602699 with a preventive catalyst
DE468402 sulphate preventive catalysts

Attached is a small DJVU file - it is russian but contains a very good drawing of a ketene lamp as used in laboratories for long times.
To get the idea and for further inspiration.

If you want more as small amounts ketene/acetic anhydride the lamp or tube is the way to go. About a liter overnight is told to be no problem with a device as described in Vogels 3rd.

:D:D:D ;);)

[Edited on 1-4-2003 by Organikum]

Attachment: Keten_lamp.djv (50kB)
This file has been downloaded 1397 times

BASF - 1-4-2003 at 15:27

Good info on the ketene process, dude.:)

I´m still worrying about the toxicity of ketene(same as phosgene), so i am hesitating at trying the ketene method.
Well, i plan to do this outside anyways, but i have lots of neighbours(which i have no war with, at the moment), so this is is another reason...

Organikum - 2-4-2003 at 12:19

Do it inside with an aspirator and two washbottles, one with acetic acid one with water. The aspirator has to produce only enough underpressure for a directed flow through the whole apparatus.
This way leaks and unhealthy ketene won´t bother you, also the methane is washed away.
As there are no corrosive chemicals involved and clogging is no problem use metal to build. This makes it easy to prevent leaks and you don´t have to fear shattering.

If you are advanced in working with glass this is not important to you, is understood. The old chemists made everything from glass because the all were glassblowers too. They had to be.

The trick is in the rapid cooling after the hot zone from >700°C to <600°C, so if a metaltube is used a thermal insulating piece of ceramics (furnace cement with silicates) or else is necessary to divide hot and cooling part.

glad if I could help so :)


madscientist - 2-4-2003 at 13:16

I'm guessing that what would happen with a SO<sub>3</sub>/acetic acid heating process would be that it would yield lots ketene gas from dehydration. H<sub>2</sub>SO<sub>4</sub>/acetic certainly seemed to do that (see the old acetic anhydride thread).

Organikum - 2-4-2003 at 17:08

I could not find the post you refer to madscientist. The thread is quite long.

After my best of knowledge SO3 bubbled into GAA yields the anhydride. Perhaps it is possible to dehydrate this further to ketene, maybe. I would propose to stop before this happens and to distill the anhydride out of the GAA. To go for a complete conversion is unrealistic.

btw. in the first thread, was this "Coen" misinforming by will or incompetence?

But SO3 is at least as nasty as ketene which is NOT to compare with phosgene. The anhydride reacts fast with every water and alone humidity is sufficient to degrade some escaped traces.

The "lamp" or tube is a safe method if tried by someone with a minimum of responsibility. Those lacking the responsibility needed will probably fail on the task to build the device. So there is more than only one advantage in this. ;)

addon: looked up some things and got this:
It is imposssible to get ketene bubbling out of GAA except you pump masses of SO3 into it very fast. Still most ketene would react with the GAA to form the anhydride. This reacts with SO3 to ketene. If the reaction is a controlled one and stopped before most GAA is anhydride no ketene is evolved.

I got the first hand tip that rapid stirring and/or a bubblestone in the receiving flask with the GAA are necessary if the lamp is used for to get all ketene to react. To use a tube instead a flask was suggested.

[Edited on 3-4-2003 by Organikum]

madscientist - 2-4-2003 at 20:17

The seemingly ancient post to which I was referring to:

I'm not sure, but I think that it's possible that I prepared acetic anhydride by accident today. I mixed 164g CH3COONa (contaminated with a small amount of NaHCO3, around 1-2g) with 75g 94% H2SO4. I then poured that into a flask; began heating it, and condensing the vapors (typical distillation). I noticed a very strange, sickly-sweet odor; very difficult to describe. I got a whiff of a very small amount of it, causing me to choke for a few moments. The condensed liquid (which I got 22mL of, if I remember correctly) was still liquid, showing no signs of imminent freezing, at -10C. Now, if that had been acetic acid, it would have frozen at a far higher temperature than that... acetic anhydride, on the other hand, would not freeze until the temperature was FAR lower. I'm postulating that the following reactions were occuring, forming at least a fair-sized quantity of acetic anhydride (there is probably a significant amount of acetic acid remaining). Keep in mind that there was a slight stoichemical excess of sulfuric acid.

2CH3COONa + H2SO4 --> 2CH3COOH + Na2SO4
7CH3COOH + H2SO4 --> 7CH2CO + H2SO4*7H2O

And of course, the following occurs:


Tomorrow I'll try droppering a small amount of the distilled liquid onto an aluminum plate; if there is no visible reaction, then it is definitely high-purity acetic anhydride. Otherwise, it contains at least a medium amount of acetic acid.

I placed a few drops of the distilled liquid on a piece of aluminum foil. No visible bubbling, or audible bubbling, resulted. It has a pH of 1, though.

Organikum - 2-4-2003 at 23:10

Sorry my fault.
Searched for "ketene" only, not the formula.

Scrubbing the fumes through GAA and distillation should solve it, also I never heard up to now of this.
Will have an closer look so time.

toxicity of ketene

BASF - 3-4-2003 at 05:23



But SO3 is at least as nasty as ketene which is NOT to compare with phosgene.

I was actually referring to this:

Sorry for the german, but this source DOES indeed compare the toxicity of ketene with that of phosgene!


H2C=C=O, C2H2O, MG. 42,04. Durchdringend riechendes, äußerst giftiges Gas (MAK 0,5 ppm, die Toxizität liegt in der Größenordnung von Phosgen), Schmp. –150°, Sdp. –56° (auch –50 od. –41° angegeben), das nur bei tiefen Temp. (–80°) einigermaßen beständig ist. Es muß daher stets frisch hergestellt u. gleich weiterverarbeitet werden, da sonst Dimerisierung zu Diketen erfolgt. K. kann durch Pyrolyse aus dem Dimeren zurückgewonnen werden, weshalb man Diketen als eine Speicherform betrachten kann; allerdings ist die Pyrolyse nicht ungefährlich u. wird auch nur selten durchgeführt. Weitere Oligomere sind 3-Acetoxycyclobutenon (Lit. ) u. Dehydracetsäure.

Herst.: Techn. wird K. durch Wasser-Abspaltung aus Essigsäure gewonnen:

Man leitet Essigsäure-Dämpfe unter Zusatz geringer Mengen flüchtiger Phosphorsäureester über CrNiSi-Stahl (ca. 700°, 130 hPa, Wacker-Verf.). Um die Rückreaktion zu verhindern, werden den Pyrolysegasen bas. Stoffe (z.B. Ammoniak, Pyridin) zugesetzt; ferner wird das Reaktionsgas rasch abgekühlt. Auch Aceton ist Ausgangsmaterial zur Herst. von K.:

Aceton-Dampf wird unter dem katalyt. Einfluß von CS2 bei ca. 650° an Chrom-Nickel-Stahl therm. zersetzt. Im Laboratorium erfolgt die Erzeugung von K. mit Hilfe der sog. K.-Lampe, bei der die Aceton-Pyrolyse an elektr. geheizten Wolfram-Drähten erfolgt.
Verw.: K. ist sehr reaktionsfähig, da es zwei kumulierte Doppelbindungen aufweist. Es wird eingesetzt zur Synth. von Sorbinsäure, Cyclobutanon-Deriv., zur Acetylierung u. zur Herst. von Acetanhydrid (Hauptverw.), gemischten Anhydriden, Isopropenylacetat u. Celluloseacetat. Die photochem. Decarbonylierung liefert Carben.

Lit.: 1 Helv. Chim. Acta 60, 975–977 (1977).
allg.: Beilstein EIV 1, 3418–3420 ï Chem. Ztg. 97, 67–73 (1973) ï DECHEMA-Monographie 42, 125–143 (1962) ï Giftliste ï Helv. Chim. Acta 53, 417–432 (1970) ï J. Chem. Educ. 53, 81–85 (1976) ï Moeschlin, Klinik u. Therapie der Vergiftungen, S. 336, Stuttgart: Thieme 1986 ï Ullmann (4.) 14, 181ff.; (5.) A1, 69f. ï Weissermel-Arpe, S. 192–196 ï Winnacker-Küchler (3.) 4, 93–94; (4.) 6, 92 ï s.a. Diketen u. Ketene.

E ketene
F cétène
I chetene
S ceteno
CAS 463-51-4
G 3

Quelle: CD Römpp Chemie Lexikon – Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995


Organikum - 3-4-2003 at 06:01

What a luck I can read it..:D

Ok, I was again expressing myself not exactly enough.
I referrred not to the actual toxity of ketene but to the realworld fact that except you live in a very very dry enviroment ketene reacts with the humidity in the air fast to acetic anhydride and this to acetic acid.
So this gas travel not long and far and if you stick your nose not very deep in the outlet of the tube you are quite safe.
This is an further advantage of the thermolytic process: the amount which is produced ad hoc is quite small and there is no danger of getting overwhelmed by an outbreak of toxic gas.

By no way I wanted to say you are misinforming, sorry.

Compounds have to be judged in the situation, amount and enviroment they exist. This was what I tried to do. Have you looked for SO3 also? ;)

BASF - 3-4-2003 at 10:16

:) hmm i have no experience with ketene, or sources lining out how to handle it....but after what you are saying it seems increasingly interesting for me...

How do you know it reacts that fast with moisture?

BTW, on the method which would involve SO3, i recall the following, -to my understanding- fairly cheap method:

2NaHSO4 ---> Na2S2O7 +H2O

Na2S2O7(sodium pyrosulfate) --->
(>400°C) Na2SO4 + SO3

.....rikkitikkitavi also mentioned that in some older posts

To give you some reference(again, sorry for it, in german):next post)

[Edited on 3-4-2003 by BASF]

BASF - 3-4-2003 at 10:45


(Natriumbisulfat, Natriumhydrosulfat). Als Monohydrat NaHSO4 · H2O, MG.138,07, farblose, große, in Wasser sehr leicht lösl. Krist. (saure Reaktion), die beim Erhitzen unter Wasserverlust zunächst in Natriumdisulfat (Natriumpyrosulfat, Na2S2O7, MG.222,16, farblose Kristallmasse, D. 2,658. Schmp. 401°, bei 460° Zers). übergehen:

bei weiterem Erhitzen entsteht Natriumsulfat unter Abspaltung von Schwefeltrioxid.
Herst.: Aus NaCl u. konz. Schwefelsäure:

Verw.: Zum Sauerstellen in der chem. Ind., Textil-, Papier-, Leder-, Kautschuk- u. Eisen-Ind., beim Färben von Wolle, zum Aufschließen schwerlösl. Verb. in der chem. Analyse, Reinigung von Platintiegeln. Herst. von Na-sulfat, in Thermophoren u. dgl.
Lit.: Gmelin, Syst.-Nr. 21, Na, 1928, S. 586–592, Erg.-Bd. S. 246f., 1150–1161 ï Hommel 1004 ï Kirk-Othmer (3.) 21, 245–255.

E sodium hydrogensulfate
F hydrogénosulfate de sodium
I bisolfato di sodio
S hidrogenosulfato de sodio
Z 2833.19
CAS 7681-38-1

Quelle: CD Römpp Chemie Lexikon – Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995

BASF - 3-4-2003 at 10:58



(Schwefelsäureanhydrid). SO3, MG. 80,06. SO3 existiert in drei Modif., die alle bei 44,8° sieden. Die g-Form (trimer) bildet farblose, durchscheinende, an der Luft stark rauchende, eisartige Massen, D. 1,995 (bei 15°), Schmp. 16,8°; g-SO3 ist metastabil u. wandelt sich bei längerem Aufbewahren unterhalb 25° um in polymeres b-SO3 (farblose, seidenglänzende, verfilzte Nadeln, Schmp. 32,5°) u. in polymeres a-SO3 (farblose Nadeln, D. 1,97, Schmp. 62°; Schmp. um ca. 17° höher als Sdp.). Das im Handel erhältliche SO3 ist meist ein Gemisch aus (viel) b-SO3 u. (wenig) a-SO3 vom Schmp. ca. 40° (nach anderen Angaben handelt es sich um g-SO3) od. eine rauchende Flüssigkeit, auf welche die Bez. Oleum (s. Schwefelsäure) zurückgeht. Sog. stabiles SO3 enthält geringe Mengen an org. od. anorg. Substanzen, die die Umwandlung in die polymeren SO3-Modif. hemmen, z.B. Thionylchlorid od. Oxalylchlorid. SO3 ist stark hygr. (starke Erhitzung, Bldg. von Schwefelsäure); fällt ein Tropfen Wasser auf SO3, so erfolgt eine explosionsartige Reaktion. Viele org. Verb. werden durch SO3 vollständig dehydratisiert; daher verkohlt z.B. Cellulose in Ggw. von SO3.

Herst.: SO3 entsteht aus SO2 bei der Schwefelsäure-Fabrikation (Kontaktverf., s. Schwefelsäure) als Zwischenprodukt. Reines SO3 wird aus Oleum durch sog. Oleostripping, z.B. durch Destillation u. Verflüssigung der Dämpfe gewonnen, wobei die Temp. von 27° nicht unterschritten werden darf, um ein Erstarren des SO3 zu verhindern.
Verw.: Zur Herst. von Chlorsulfonsäure (s. Chloroschwefelsäure), Thionylchlorid, Amidoschwefelsäure, Dimethylsulfat, zur Sulfonierung org. Verb., insbes. in der Waschmittel-Ind. (lineare Alkylbenzolsulfonate). Im Laboratorium verwendet man zu Sulfonierungen oft Addukte von SO3 an Dioxan, Pyridin od. Dimethylformamid.

Lit.: Encycl. Gaz, S. 1139–1144 ï Gmelin, Syst.-Nr. 9, S, Tl. A, 1942–1953, S. 320–484, Tl. B, 1953, S. 323–367 ï Hommel Nr. 184 ï Synthesis 1979, 699f. ï VDI-Richtl. 2462/8 (März 1985) ï s.a. Schwefelsäure.

E sulfur trioxide
F trioxyde de soufre
I anidride solforica
S trióxido de azufre
Z 2811.29
CAS 7446-11-9

Quelle: CD Römpp Chemie Lexikon – Version 1.0, Stuttgart/New York: Georg Thieme Verlag 1995

Organikum - 4-4-2003 at 04:03

Badische Anilin und Soda Fabrik wrote regarding ketene:

How do you know it reacts that fast with moisture

I assumed the MERCK index to be true. :D

And I got some first hand information on the lamp. The very high reactivity with water was stated, I was warned by one experimentor not to expect to high a reactivity with GAA and to use an effective bubbler/stirrer and a tube as receiving vessel plus a gas scrubber filled with water/lye.

My concept included always an aspirator to direct and enhance gasflow by minimizing the danger of excess overpressure building up in the system. The aspirator disposes also the methane produced by the process and provides a second way to control the velocity of the acetone and the time it stays in the hot-zone of the tube whats the keypoint of the reaction.

Of course would burning the methane to heat the tube be the most sophisticated and elegant solution but a short look at the necessary effort in construction shows that this would destroy the genial simplicity of the device as is. ( the fact that the practical realization of this is would be far out of reach for me may have played another, minor role in the decision ;)). And open flames would afford the apparatus to be watched all time. Watching the washing machine washing is exiting compared to this and I tend to fall asleep in meditations also....
(sleep is wrong, "state of ultradeep concentration" is better)

Conclusion: If you want acetic anhydride build the ketene lamp like described in VOGELs 3rd just use pottery/clay/furnace cement or similar instead glass for the reaction chamber, incascient lamps, glass broken away three in line (try) for a dull red glow can be used as I was told, but if you realy can´t get an old electroheater or hairdryer to abuse, PM me I have some left over. The rest can be made from metal with ease, copper is fine, don´t use labglass but solder a "one piece no leaks" unit. An aspirator at end of the line is favourable.
Take VOGELs dimensions and build it in half a day if you have soldered copper tubing before.
If you cannot solve the problem how to get a virtual leakfree connection of reaction chamber (ceramics) and coppertube you should forget to build and run a ketene producing apparatus.

One challenge must be left.

The tube has the advantage to be the higher intellectual task, to give much more possibilities to play with parameters ( no danger involved) and to be a universal device. Most so urgently wanted but restricted compounds or their precursors can be made by pyrolytic reactions. This is truely worth a look.

next month:
"Der Stein der Weisen" in three hours utilizing a microwave. :D

BASF - 8-8-2003 at 04:38

Hmm... could you explain your idea with a practical example?

This could be interesting, but aren´t these kinds of anhydrides all made using P2O5, PCl5 and so on?
Correct me, if i´m wrong(would be pleasing:))

A caution on Oleum and SO3 in general

Mr. Wizard - 10-8-2003 at 07:51

I've never used Oleum in a laboratory setting. I have had the opportunity to see 10 gallons, wheighing over 200 pounds, spilled into a metal pan at a DuPont haz mat conference. The resultant plume of thick white smoke, a hundred yards wide, extending for a few miles, was thick enough to completly block sunlight, and kill birds unlucky enough to fly through it. Yes, I said miles. The demonstration ended as crews in protective suits approached the tank with firehoses and flooded the liquid, resulting in explosions of steam and acid which knocked a few men down as they held the hoses. The diluted acid was then neutralized with soda lime. This is not a scenario I would wish to see repeated in someone's garage with even a small amount of oleum. Chlorosulfonic acid did exactly the same thing. :o If you must experiment, make the quantities very small and plan for the worst case scenario.

Whoops....oh s**t!

KABOOOM(pyrojustforfun) - 15-9-2003 at 13:58

extracted from <i>the condensed chemical dictionary</i> (I write the important parts in bold italic):<br><b>acetic anhydride</b> (acetyl oxide;acetic oxide)<br>&nbsp;&nbsp;(CH<sub>3</sub>CO)<sub>2</sub>O. 48th highest-volume chemical pro-<br>&nbsp;&nbsp;duced in U.S. (1979).<br>&nbsp;Properties: Colorless, mobile, strongly refractive<br>&nbsp;&nbsp;liquide; strong odor; sp. gr. 1.0830 (20/20°C); b.p.<br>&nbsp;&nbsp;139.9°C; f.p. -73.1°C; flash point 121°F (49.4°C)<br>&nbsp;&nbsp;(C.C.). Autoignition temp. 732°F (385°C); wt/gal<br>&nbsp;&nbsp;(20°C) 0.01 lbs. Miscible with alcohol, ether, and<br>&nbsp;&nbsp;acetic acid;<i><b> solouble in cold water; decomposes in <b>hot</b><br>&nbsp;&nbsp;water to form acetic acid.</i></b> Combustible.<br>&nbsp;<i><b>Derivation: (a) oxidation of actaldehyde with air or<br>&nbsp;&nbsp;oxygen with catalyst; (b) by catalyzed thermal<br>&nbsp;&nbsp;decomposition of acetic acid to ketone; (c) reaction<br>&nbsp;&nbsp;of methyl acetate and carbon monoxide; (d) from<br>&nbsp;&nbsp;carbon monoxide and methanol.</i></b><br>&nbsp;Grades: C.P., technical(75, 85, 90-95%).<br>&nbsp;Containers: Bottles; carboys; aluminum drums; tank<br>&nbsp;&nbsp;cars.<br>&nbsp;Hazards: Strongly irritating and corrosive; may cause<br>&nbsp;&nbsp;burns and eye damage. Tolerance, 5 ppm in air.<br>&nbsp;&nbsp;Moderate fire risk.<br>&nbsp;Uses: Cellulose acetate fibers and plastics; vinyl<br>&nbsp;&nbsp;acetate; dehydrating and acetylating agent in pro-<br>&nbsp;&nbsp;duction of pharmaceuticals, dyes, perfumes, ex-<br>&nbsp;&nbsp;plosives, etc.; aspirin. Esterifying agent for food<br>&nbsp;&nbsp;starch (5% max.).<br>&nbsp;Shipping Regulations: (Rail, Air) Corrosive label.<br>
Coen was going to give some info on acetaldehyde methode. plEASE do it. mixing GAA & acetaldehyde and bubbling air to get Ac2O makes too much sense. just need to know about its catalyzer. the CO methodes seem very interesting too but don't have any furthur info. I strongly need googlin around!

BASF - 16-9-2003 at 05:50

Another interesting method:

Quite interesting...this is how chemistry attempted to produce sodium carbonate along with acetic anhydride in the 30ies.

2NaAc + CO2>(saturated alcoholic solution, <20°C) Na2CO3 + Ac2O(along with some acetic acid, depending on the initial water content), preferably in a counterflow apparatus.

Generally, (british) patents of the 30ies seem to be a good source for alternative, often chemically very simple methods...


BASF - 17-9-2003 at 04:36

Maybe a good book that was mentioned here, although Vogel´s book about preparative chemistry might do the job...

BTW, it´s here on the FTP, right? :)

Al Koholic - 29-9-2003 at 17:00

I'm really wondering if anyone has tried the method 2 posts up? It seems odd to me that people follow all these "exotic" and "dangerous" methods to Ac2O when this exists. Additoinally, after spending countless hours on Beilstien over a long period and looking up every reaction I think I would ever want to accomplish and then some...I have never even seen this associated with Ac2O. I'm going to have some experimenting to do...I'll post results but would like to hear if anyone has done this!



I just wanted to add that after thinking about this method it makes complete sense and I have a good amount of confidence that yield will be good too. I noticed that the CO2 will be highly susceptible to nucleohpilic attack by the acetate oxygen. When an intermediate forms will then be attacked by a second acetate at the carbonyl carbon kicking off CO3 which due to resonance will be very good leaving group. Immediate uptake of 2 Na+ cations willl result in the completely insoluble Na2CO3 which willl cause any equillibrium which might have existed to be FAR to the right. Seems like the reaction has everything going for it...

Yes I know...this is my first post. I've been a member here for quite some time just haven't been active. Anyway, I look forward to future discussions with all ya'll as I will be here more frequently...
[Edited on 30-9-2003 by Al Koholic]

[Edited on 30-9-2003 by Al Koholic]

BASF - 1-10-2003 at 05:37

It´s on my to-do-list too, but i don´t know how long it will take til i grab some time for experimenting.
Maybe sylvester??
However, it is nice to hear somebody attempts to try this method too(and has a little knowledge about organic chem:P)

I was only wondering how it would be possible to seperate the Ac2O from etOH.
-Wouldn´t it react to give ethyl acetate?

Maybe we can salt it out with sodium acetate or something?? - But then it is contaminated with the salt and it would have to be distilled off.

But yes, THIS patent fascinates me the most.

[Edited on 1-10-2003 by BASF]

Al Koholic - 1-10-2003 at 16:17

Hmmm that slipped by me...yes the alcohol will react with the formed Ac2O to form ethyl acetate. I'm not sure how fast this reaction will proceed though and it could in fact be quite slow if the temp is kept down who knows. I remember once reading a patent for Ac2O production that generated water in situ but since the whole procedure was kept at such a low temp they had some time on their hands to remove the product before it was noticably hydrolysed. I however do not think I want to be worrying about this type of thing with a prep.

My other idea is to use some solvent other than alcohol. Perhaps pyridine would work...

HOAc should dissolve quite well in pyridine (being basica and all) and yield acetate anions. Now bubbling CO2 through would kinda work the same way but I would be concerned that instead of making Na2CO3 as a by-product we would be making H2CO3 which would just split to H2O and CO2 again hence hydrolyzing the product. Hmmm...

Or perhaps the formation of carbonic acid would be stable if it complexed with the pyridine.

This is all just thinking off the top of my head here unfortunately. I have no idea what the real effects of a reaction like this would be...must have to experiment sometime with it I suppose. At least any Ac2O formed wouldn't react if it does work the way I hope it would...

My ketene lamp

Flayer - 22-4-2005 at 04:40

ketene.jpg - 187kB

Esplosivo - 22-4-2005 at 05:35

Interesting, care to elaborate how this works out. I gather that acetone is passed through the hot copper tube for pyrolysis, but what are the rest of the connections, and how is the ketene vented to acetic acid? Thanks.

I am myself preparing a ketene generator on a larger scale so to produce at least 1Lt of acetic anhydride per run (relatively short time of say 5 hours). I intend to use a set-up as shown on patents mentioned by Organikum, using gas heating (since electricity where I live is expensive and totally unreliable, and gas is cheap). I will post about this project at around mid-summer, when I hope I will have completed the whole thing.

vulture - 15-6-2005 at 12:52

This may be slightly off-topic, but I don't think it warrants a new thread.

My Roempp chemical dictionary claims acetylchloride can be made from acetic anhydride and CaCl2, however, no procedure is listed and google doesn't seem to know the answer either.

S.C. Wack - 15-6-2005 at 13:24

I came across a reference somewhere else, it may be what they are talking about. The yields in this article are not the greatest.

Attachment: helv_chim_acta_36_2021_1953.pdf (28kB)
This file has been downloaded 1712 times

CD-ROM-LAUFWERK - 21-6-2005 at 01:08

P2O5 and GAA dont reakt to the anhydrid or keten!
the BP. of the GAA was than 110°C :o

I would then propose distilling off the rests of SO3 at moderate temperature(can be recycled by dissolving in conc. H2SO4), followed by distilling off as much of the lower boiling acetic acid as possible and then the last fraction should yield an azeotropic mix of acetic anhydride and acetic acid, which is far from being pure acetic anhydride i presume, but i´m sure it could be used in most nitrations where acetic acid is added to the anhydride anyway.

u cant destill SO3 out of H2SO4 that easy,
the lower the SO3 conz. is, the higher is the temp. u need to destill it off from H2SO4
means: the last % SO3 destills over near the BP. of H2SO4 :(
u also cant destill the GAA or the anhydrid out that easy...
its the same as when u try to destill HNO3 out of H2SO4, the more H2SO4 u use, the higher is the temp. that is need to destill the HNO3 out, but HNO3 isnt stabel anymore at >150°C so u have much NO2 in it :(
same hapens whit the GAA (and the anhydrid?) the stuff just gets dehydratet to carbon!

unionised - 21-6-2005 at 11:39

I'm intrigued by the idea that, because ketene reacts with water, it can't be a real health hazard.
Phosgene also reacts with water but worked adequately well as a war gas.
Methyl isocyanate reacts violently enough with water to blow up factories like Bhopal. That didn't seem to stop it causing further damage to a lot of people.

Dave Angel - 24-7-2005 at 10:42

I've been tinkering around with a ketene lamp set up for a while now but only just made a first run.

I'm using a coil from a heat gun which I've trimmed down to fit through a 34/35 joint into a 3-neck flask. The 19/26 side necks take an addition funnel and condenser. The wires for the coil come out of the side arm of a T-shape adapter, 34/35c-19/26s, having a side arm for push on hoses. I use the 19/26 socket to feed argon in before plugging it and running the set up.

Aside from the coil being in the boiling flask (permitting very little acetone to be in the system at one time) the set up is otherwise much like Vogel's.

Having purged the system with argon and refluxed the acetone a little, I turned the coil on and made the following observations.

The hot melt glue used to seal the gap where the wires come out leaked and melted in spite my efforts to cool it with damp cloth or duct/PIB tape it up. I had expected this to be the weakest point and it was what ultimately made me turn the thing off after about 30 mins.

During use, a light grey 'mist' went up the primary condenser (water-coil) and down the secondary, air condenser. Some liquid (~1 mL) collected in the separating funnel.

The gases were passed through hot, deionized water (500 mL) and then burnt. The end gases were very flammable and the water became quite acidic (indicator solution goes fully red) but with minimal, if any, change in density.

Having turned the thing off, the coil had become coated in some hard soot. Interestingly it was clean close to where the acetone pooled in the bottom of the flask and more carbonised higher up.

I took my mask off for a moment to see how the air was (after opening the apparatus up) and the smell was something like that spray foam string stuff you can get for parties etc. The small volume of liquid that was collected also smelt strongly, perhaps slightly different to the air or perhaps just more concentrated.

So there's some issues to work out in order to make a long run safe and productive:

The wires. I've thought of epoxying them in, but that has a certain finality to it and may still not stand the heat. Any other thoughts?

Carbonisation. A little oxygen creeping in? Over-decomposition? The coil was at a dullish red glow with the variac on 45% so lower/higher is easy to try out.

Liquid collecting: Ketene polymerisation products? If not, acetone may be escaping the condenser, which isn't ideal, but can probably be separated later.

Another concern is that there is nothing forcing/drawing the gases through the system. If they hang about in the boiling flask too long they may be decomposing to far, causing the carbonisation. Maybe some suction at the end?

Any ideas?

neutrino - 24-7-2005 at 11:45

If there was any moisture in your apparatus (from the glue, maybe), that liquid would probably be acetic anhydride.

sparkgap - 24-7-2005 at 18:09

Isn't diketene a liquid also?

sparky (~_~)

Dave Angel - 26-7-2005 at 06:29

I doubt it's AA; it smells nothing like it and even if something were masking the smell it would still have a stinging effect on the nose and eyes.

We are thinking the same thoughts sparkgap... diketene is a distinct possibility and it's formation after the condenser would explain how it escaped reflux.

I can't seem to freeze it, even at -20°C, (mp -7°C to -6.5°C), but that may be due to impurities, maybe some escaped acetone. I tried decomposition in water but the smell of the sample is close to that of acetone and so that particular test is difficult to detect. I did think I smelt acetone strongly from it the first time I tested this, but I came back later, tested it again and wasn't so sure. Perhaps it had further polymerised to the point where it did not decompose in water. It also causes a pH drop in water so I may be getting no ketene to interact with the water later on in the apparatus.

I have managed to solve a couple of problems, in my head at least.

I intend to feed the coil wires up through a 34/35 reflux condenser with a plain end. There at the top, the joint will be safe from conducted heat due to distance and, if I run the condenser, hot acetone.

I also intend to apply something of a vacuum to the end of the set up to draw the vapours through. I'm not too sure about using a full vacuum though, as that will make the acetone more difficult to reflux.

So those are the major hurdles, I should be able to make another attempt as soon as I make the new ideas reality and clean this crap off the coil!

sparkgap - 27-7-2005 at 03:01

I checked the container of diketene in my lab the other day and was able to confirm that it is indeed liquid at ambient conditions.

"...It also causes a pH drop in water..."

IIRC, diketene hydrolyzes to acetoacetic acid in water. That may be it. ;)

sparky (~_~)

Dave Angel - 27-7-2005 at 07:06

Thanks for the info. From what I could find, diketene is said to decompose into acetone and CO2 - which, it is now clear, must come from decarboxlyation of initially produced acetoacetic acid! The acetone was what I was trying to detect (to indicate possibility of it being diketene), above, but perhaps it needs to be sealed up with water, heated and allowed to decarboxylate.

I guess the acetoacetic acid and then dissolved CO2 would produce the acidity, certainly acetone only produces a yellow colour with indicator solution. This is the problem you see; I was relying on the pH change to indicate ketene interacting with my flask of deionized water to produce acetic acid. With diketene having the same effect it's going to be tougher to determine if ketene is being produced. Hopefully the measures I've outlined above will minimise the chance for diketene formation.

I'm attaching a view of the set up. I also have closeups of areas that I can post if anyone is interested.

[Edited on 7/27/2005 by Dave Angel]

wholesetup.jpg - 260kB


ballzofsteel - 28-7-2005 at 05:55

For those benzal chloride buffs out thar.
Dont know if this is within the scope of this thread,but it seems easier than acetylchloride/ketene methods.
Sorry if this has been posted previously.

161 parts of benzalchloride are heated with 180 parts of thoroughly dried sodium acetate for 14 hours at 160-170 (C'. The product is worked up by distillation and in this manner considerable proportions 50 of acetic anhydride and beuzaldehlyde are isolated.

The patent says that the addition of GAA can improve yield to 90% blah blah blah.


CD-ROM-LAUFWERK - 6-8-2005 at 23:56

i found this text in the ullmann 7th edition:

Production via Ethylidene Diacetate. Addition of acetic acid to acetylene in the presence of mercury(II) salts yields ethylidene diacetate [542-10-9], CH3CH(OCOCH3)2, which decomposes into acetaldehyde and acetic anhydride at 130 – 145 °C in the presence of acid catalysts (e.g., ZnCl2). This process was developed by the Societe Chimique des Usines du Rhône on an industrial scale in 1914 but is now without importance.

there are no reaktion informations, such as temperatur and pressur, given,
but i hope u guys know them ;)
so, is it possible to buble C2H2 into GAA, in the presence of Hg2+ cat., at temperaturs under the bp. of GAA and normal pessur to get ethylidene diacetate?

i searched now a while and found some intresting things:
the temperatur is 60-100°C and the salz used was mercurysulfate (suspension in the GAA?)

[Edited on 7-8-2005 by CD-ROM-LAUFWERK]