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Waffles SS
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| Quote: |
The mixture is then subjected to decomposition at a temperature of about 250 to 270 c under an absolute pressure of about 10
to 15mm hg
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I tried acetate salts Pyrolysis under vacuum method but only salt that made AC2O was silver acetate.I think Henry Dreyfus was mad and he published
lie full patents during 1922-1937(like US1430304 for making anhydrid from pyrosufate salt)
Maybe on 1922 everyone was able to publish everything!
| Quote: |
Band 61 B5, Seiten 125-6.
2.2.7.2 Thermische Zersetzung
Die Zersetzung von AgCH3COO, die bereits von Chevenix [1] beim Erhitzen über einer Kerzenflamme (starker Geruch nach Essigsäure) beobachtet wurde,
setzt bei 210°C ein (Dunkelfärbung), erfolgt hauptsächlich zwischen 220 und 240°C und ist vollständig bei etwa 300°C [2]. Beim Erhitzen im
offenen Rohr oder im bedeckten Porzellantiegel werden als Zersetzungsprodukte im wesentlichen Essigsäure und Ag neben wenig C02 und C beobachtet
entsprechend 4AgCH3COO ->4Ag + 3CH3COOH + CO2 + C [3 bis 5]. Von Kachler [2] werden als Reaktionsprodukte gefunden (in Gew.-%, nach vorstehender
Gleichung berechnete Werte in Klammern): 64.61 Ag (64.67), etwa 26 bis 27 Essigsäure (26.95), 4.09 bzw. 8.42 CO2 (6.59) und 1.21 C (1.79). Auch bei
thermogravimetrischer Untersuchung wird als Zersetzungsprodukt (bei 280°C) metallisches Ag und kein Ag2O erhalten [6]. Erfolgt die Zersetzung jedoch
unter streng wasserfreien Bedingungen, so werden als Zersetzungsprodukte nur Ag2O und Essigsäureanhydrid erhalten nach 2AgCH3COO -> (CH3CO)2O +
Ag2O. Bei der Zersetzung von 2.1077 g trocknem AgCH3COO bei 300 bis 400°C in einem Quarzgefäß unter Argon (1 atm) werden nahezu quantitativ Ag2O
(96% der Theorie) und Essigsäureanhydrid (93%) gebildet neben wenig Ag (0.012 g) und CO2 (0.016 g) [7]. Die primäre Essigsäureanhydridbildung ist
bereits von Kanewskaja, Schemiakin [8] bei Untersuchung der thermischen Zersetzung von AgCH3COO (im Gemisch mittrocknem Sand) unter einem CO2-Strom
von 20 bis 25 Torr angenommen worden. Zwar fanden diese Autoren nur wenig Essigsäureanhydrid neben viel Essigsäure (entsprechend den früheren
Angaben von Kachler [2] und Iwig, Hecht [4]), doch ist dies auf die leichte Hydratisierung des Essigsäureanhydrids zurückzuführen, die sowohl durch
H2O-Spuren in dem schwer zu trocknenden Silberacetat als auch durch H2O erfolgen kann, das beim teilweisen Zerfall der Essigsäure gebildet wird.
Für die vollständige thermische Zersetzung von AgCH3COO in Gegenwart von H20 muß auf etwa 230 bis 340°C erhitzt werden. Abweichend von der
trocknen Destillation wird neben den Hauptprodukten der Zersetzung Ag, Essigsäure und CO2, kein Kohlenstoff gefunden [2].
Über die Darstellung von Ag-Schwamm durch Erhitzen einer getrockneten Paste von AgCH3COO im Tiegel auf 400 bis 500°C s. [10].
...
[1] R. Chevenix (Ann. Chim. [Paris] 69 [1809] 5/58, 19, 22; Ann. Physik 32 [1809] 156/201, 167, 179). — [2] J. Kachler (Monatsh. Chem. 12 [1891]
338/49, 340). — [3] K. Birnbaum (Ann. Chem. 152 [1869] 111/21, 119). — [4] F. Iwig, 0. Hecht (Ber. Deut. Chem. Ges. 19 [1886] 238/42). — [5] J.
Redtenbacher, J. Liebig (Liebigs Ann. Chem. 38 [1841] 113/40, 131).
[6] D. A. Edwards, R. N. Hayward (Can. J. Chem. 46 [1968] 3443/6). — [7] A. D. Kirschenbaum, A. G. Streng, M. Hauptschein (J. Am. Chem. Soc. 75
[1953] 3141/5, 3143).— [8] S. J. Kanewskaja, M. M. Schemiakin (Ber. Deut Chem. Ges. 69 [1936] 2152/7, 2154). — [9] V. I. Yakerson (Izv. Akad. Nauk
SSSR Otd. Khim. Nauk 1963 1003/11, 1007; Bull. Acad. Sei. USSR Div. Chem. Sci. 1963 914/21, 916). — [10] T. Yamanaka, H. Nidorikawa (Japan.P. 6720
[1956] nach C.A. 1958 10462).
http://www.sciencemadness.org/talk/viewthread.php?tid=9&...
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[Edited on 27-12-2011 by Waffles SS]
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peach
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Thanks for the reply Waffles.
I would have preferred to do it at 10-15 mm but was seriously concerned about just how mobile the powders were, and them potentially ending up in the
pump, grinding away. And also the difficulty of trapping the liquids.
I didn't see too much of a problem in doing it around 80, which reduced the temperature right down to about as low as I could trap any liquid and,
with it being a diaphragm pump, it'd be easier to clean out if it did end up full of muck. Neither should there be a whole lot of moisture present
relative to the amount of anhydride the mass of salts should produce.
When you tried the copper salts, did you allow those to dry under hard vacuum for hours and use them immediately? The only major source of moisture I
can think of in my try would be the salts themselves. Both the salts can be dried to anhydrous, and the acetate did decompose to copper / an oxide of
copper.
Anyway, I will likely be following this up soon. I am interested in filtering the results, with some water. If all of the acetate has decomposed to
some form of copper or oxide thereof, I should end up with that stuck in the filter and can have a look at the mass. And then the mass of sulphate.
Looking at the wiki for copper sulphate, I think it's possible I still had some mono hydrate as I doubt the temperature of mine went much over 200C
when drying. I could have been rougher with that.
I have been having an investigate into the Henry Dreyfus of this patent.
I discovered there is a postdoctoral awards program named after himself.
Indeed, there is even a wiki page.
Here.
The topic at hand and the dates suggest this is the same Henry Dreyfus.
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Waffles SS
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My dear friend peach,
I used Merck anhydrous Copper(II) Sulfate and also Anhydrous Copper acetate(Indian lab chemical)
I reached 10mmhg by Edwards high vacuum Pump and i used full stainless steel Distillation System.i repeated several times this method but every time i
got acetic acid.i strongly advise that dont waste your time by this method.i suggest you Ethylidene diacetate method because i tried it and that was
successful and easy method
US1720184 best and easier way for make Ethylidene diacetate
US1578454 best and easier way for make Ac2O from Ethylidene diacetate
For testing Ac2O: just add one drop of it in water and watch it.it should fall down and reach at bottom of beaker and make very small oxygen balloon
on it head.(i hope you understand what i mean)also it has very pungent odor(like garlic odor for me!)
Attachment: US1578454.pdf (153kB)
This file has been downloaded 1099 times
Attachment: US1720184.pdf (186kB)
This file has been downloaded 1040 times
[Edited on 27-12-2011 by Waffles SS]
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Formatik
National Hazard
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There is quite a bit of info on copper acetate in Gmelin (Cu [B], 683) also:
| Quote: | - Beim Erhitzen des Monohydrats auf 140º unter vermindertem Druck werden die letzten Spuren
H2O vertrieben. Oberhalb 160º erscheinen weiße Dämpfe, die sich als wasserklare Fl. kondensieren.
Diese Fl. wird später durch sublimiertes CuCH3CO2 (vgl. S. 677), das bei 180º bis 185º erscheint,
blau gefärbt. Bei 220 bis 230º treten in reichlicher Menge CO2 und CO neben wenig KW-Stoffen auf.
Nach längerem Erhitzen auf 270º erscheint kein Destillat mehr. Das bei Drucken unterhalb ~ 80 Torr
erhaltene Destillat besteht aus 13.3 bis 15.2% H2O, 5.8 bis ~6.4% (CH3CO)2O und 35.8% bis 38.2%
CH3CO2H sowie Spuren von Aceton. Oberhalb ~80 Torr nimmt die Ausbeute von (CH3CO)2O
zugunsten derjenigen an CH3CO2H ab und wird oberhalb 300 Torr gleich Null. Die beste
Ausbeute an (CH3CO)2O wird beim Erhitzen im Vak. von ~10 Torr und einer Aufheizgeschw.
von 0.5º/Min. erhalten. Der hellbraune, pulverförmige Dest.-Rückstand enthält im Mittel
83.7% Cu, 9.1% C, 1.4% H2 und 5.9% O2, T.-Y. Chang, P. Kao (J. chem. Engg. China 4 [1937]
160/3). |
Basically above about 80 Torr the yield of Ac2O decreases in favor of more AcOH yield, where at 300 Torr Ac2O is about zero. The best yield (I don't
know what that is, see original reference) of Ac2O is obtained by heating in a vacuum at ~10 Torr (10 mmHg) and a heating rate of 0.5º/min.
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Waffles SS
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@Peach,I hope you success in your experience but i am not sure that you get Ac2O, try to reach 10mmhg in pyrolysis step(if you success then i will
find out that my Copper acetate or sulfate was hydrated and i will try this method again)
Please share your result with us
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peach
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| Quote: | | I tried acetate salts Pyrolysis under vacuum method but only salt that made AC2O was silver acetate |
Did you try any other salts that are mono acetates?
Thanks again Waffles and Formatik.
I was again chatting with the other SM member about the points you made and the odd results. I have had a closer look at the results;
I left the reactants in the flask until they were back at room temperature prior to emptying them out. Let's see what's inside!
<a href="http://img818.imageshack.us/i/img2088h.jpg/" target="_blank"><img src="http://img818.imageshack.us/img818/7792/img2088h.jpg"
width="400" border="0"/></a><br>
Redissolving in about 100ml of water, and then the remains rinsed through the funnel with another 100.
<a href="http://img402.imageshack.us/i/img2089ai.jpg/" target="_blank"><img src="http://img402.imageshack.us/img402/4627/img2089ai.jpg"
width="400" border="0"/></a><br>
<a href="http://img851.imageshack.us/i/img2090p.jpg/" target="_blank"><img src="http://img851.imageshack.us/img851/4425/img2090p.jpg"
width="400" border="0"/></a><br>
<a href="http://img528.imageshack.us/i/img2091v.jpg/" target="_blank"><img src="http://img528.imageshack.us/img528/8206/img2091v.jpg"
width="400" border="0"/></a><br>
The insoluble products.
<a href="http://img220.imageshack.us/i/img2092y.jpg/" target="_blank"><img src="http://img220.imageshack.us/img220/5100/img2092y.jpg"
width="400" border="0"/></a><br>
Copper sulphate is clearly still present.
<a href="http://img560.imageshack.us/i/img2093cg.jpg/" target="_blank"><img src="http://img560.imageshack.us/img560/3003/img2093cg.jpg"
width="400" border="0"/></a><br>
<a href="http://img827.imageshack.us/i/img2094oi.jpg/" target="_blank"><img src="http://img827.imageshack.us/img827/4213/img2094oi.jpg"
width="400" border="0"/></a><br>
<a href="http://img217.imageshack.us/i/img2096k.jpg/" target="_blank"><img src="http://img217.imageshack.us/img217/3047/img2096k.jpg"
width="400" border="0"/></a><br>
<a href="http://img696.imageshack.us/i/img2097eg.jpg/" target="_blank"><img src="http://img696.imageshack.us/img696/1306/img2097eg.jpg"
width="400" border="0"/></a><br>
I removed the water at 75 to 100C. I did this in an Erlenmeyer precisely so as to avoid any splatters leaving the clean up. I even went to the trouble
of rinsing that drip off the end of the thermometer and back into the flask.
<a href="http://img846.imageshack.us/i/img2098h.jpg/" target="_blank"><img src="http://img846.imageshack.us/img846/2182/img2098h.jpg"
width="400" border="0"/></a><br>
The filter has been sat in the oven all day to dry the cake out.
<a href="http://img830.imageshack.us/i/img2099y.jpg/" target="_blank"><img src="http://img830.imageshack.us/img830/8641/img2099y.jpg"
width="400" border="0"/></a><br>
That's good. I had 9.02g of copper going in. Copper which had in part been obtained from the results of the last try of this, and the other part
coming from when I ran the cell generating the acetate. Some of the copper going in was likely elemental copper, whereas this will be oxide (I may try
redissolving it in a bit to check that).
<a href="http://img3.imageshack.us/i/img2100qw.jpg/" target="_blank"><img src="http://img3.imageshack.us/img3/3659/img2100qw.jpg" width="400"
border="0"/></a>
To obtain a usable mass from the sulphate, I needed it get it into a hydration state I could be more sure of. So it was redissolved into a small
volume of water, emptied into a preweighed dish and the flask rinsed a few times to make sure it was all across. This way we can be sure, it is fully
hydrated at this point in time.
<a href="http://img254.imageshack.us/i/img2101t.jpg/" target="_blank"><img src="http://img254.imageshack.us/img254/2050/img2101t.jpg"
width="400" border="0"/></a><br>
The mass of the dish prior to adding the solution of sulphate.
<a href="http://img534.imageshack.us/i/img2102kg.jpg/" target="_blank"><img src="http://img534.imageshack.us/img534/8195/img2102kg.jpg"
width="400" border="0"/></a><br>
<a href="http://img546.imageshack.us/i/img2103e.jpg/" target="_blank"><img src="http://img546.imageshack.us/img546/8383/img2103e.jpg"
width="400" border="0"/></a><br>
<a href="http://img202.imageshack.us/i/img2104gy.jpg/" target="_blank"><img src="http://img202.imageshack.us/img202/5554/img2104gy.jpg"
width="400" border="0"/></a><br>
The sulphate begins loosing water of crystallisation at 63C, so I loaded it into the oven on the 50C defrost setting with the door open, checking the
temperature. Then, going to bed, left it on top of the radiator (40C). I should have largely the pentahydrate.
<a href="http://img249.imageshack.us/i/img2105et.jpg/" target="_blank"><img src="http://img249.imageshack.us/img249/1492/img2105et.jpg"
width="400" border="0"/></a><br>
<a href="http://img838.imageshack.us/i/img2106hr.jpg/" target="_blank"><img src="http://img838.imageshack.us/img838/5181/img2106hr.jpg"
width="400" border="0"/></a><br>
This is interesting, because I did not spill a single drop of the sulphate. Nor did I come anywhere close to boiling it. Yet it is climbing the sides
of the dish. There is something worry with the mass here!
<a href="http://img46.imageshack.us/i/img2109v.jpg/" target="_blank"><img src="http://img46.imageshack.us/img46/1924/img2109v.jpg"
width="400" border="0"/></a><br>
This all looks blue to me, in person. But I see the camera has picked up a faint trace of green in a spot there.
<a href="http://img848.imageshack.us/i/img2110b.jpg/" target="_blank"><img src="http://img848.imageshack.us/img848/2702/img2110b.jpg"
width="400" border="0"/></a>
Copper acetate and oxides
Those look okay. It appears the acetate has decomposed.
When distilling the results, my empty flask weighed 18.13370 and it was 22.26773g when full. Giving a mass of 4.13403g for the liquid I distilled off.
The sulphate
Having added 16.0546g of acetate to the flask, I then added around 60% w/w of the (supposedly) anhydrous copper sulphate, with the final mass
displayed being 25.0738g. That indicates an addition of 9.0192g anhydrous sulphate.
Here's the problem.
Prior to adding the sulphate to my dish, the dish weighed 51.67447g. After filling it and allowing the water to gently evaporate off, it now weighs
59.63433g. The mass change is 7.95986g.
That is an entire grams worth of sulphate missing between those two.
And far worse, the sulphate should now weigh considerably more given that it is in the pentahydrate state.
In fact, assuming my original mass of sulphate was anhydrous;
9.0192g in / 159.62 g/mol (anhydrous) = 0.05651 moles
0.05650 moles in x 249.70 g/mol (pentahydrate) = 14.1091g out
If the sulphate has not actually taken part in the reaction beyond absorbing moisture, that is 6g of error.
[Edited on 30-12-2011 by peach]
<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced
image size(s)]
[Edited on 9.12.13 by bfesser]
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Waffles SS
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@Peach,
I just tried successful Silver Acetate Pyrolysis(as mono acetate state)
I like your glassware(it seems you are well equipped)My glassware joint is not suitable for vacuum work and all of that have leak(here all of
glassware made on china and has leak).What is brand of your glassware?Schott?isoglass?
good for you
Again you got acetic acid?
[Edited on 31-12-2011 by Waffles SS]
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peach
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I believe so.
The melting point of what has been produced was too low for GAA, by a reasonably large gap. I can't find a graph of acetic's melting points right now,
but I estimated the water content must be on the order of 4.8%+. Which would put it's molarity at around 17.2M. Whereas I found mine to be 17.9M. That
instantly made me want to think the melting point being down was the result of the liquid actually being GAA with a small amount of anhydride in it,
which would drastically depress the melting point and also increase the measured molarity.
But, to measure the molarity, I used a 1ml syringe to collect the sample of raw liquid, which won't have been all that accurate and could account for
the slight difference in molarities.
If it was true that this was GAA with a small amount of anhydride in it, that does not combine well with the atmospheric boiling point I measured,
which was actually below that of GAA. The anhydride boils a good amount above GAA. If anything, had it been GAA with anhydride, the temperature should
have been at that of GAA or slightly over it.
So I'm going with, it's about 95.2% acetic.
The glassware comes from numerous places. I even have US and UK glass suggestively greased up sliding into one another.
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cal
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Acetic anhydride
Quote: Originally posted by madscientist  | | I'm theorizing that concentrated acetic acid could be dehydrated to acetic anhydride by mixing with concentrated sulfuric acid; then heating, and
condensing the vapors, yielding acetic anhydride. Any comments or additional ideas? |
Youtume has avideo on making it.
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Vikascoder
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Well i was reading some chemistry organic books in O.P Tandon i found that acetic anhydride can also be prepared from sulphuric acid and glacial
acetic acid . Will someone please tell me about this process.
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cal
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Acetic anhydride
Check you tube for the video on it.http://www.youtube.com/watch?v=p6OZ2vLxHDo&playnext=1&list=PL42B498CA5569E3CC&feature=results_video
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detonator
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I only know that these feasible solutions:
Acetic anhydride is produced by carbonylation of methyl acetate:[3]
CH3CO2CH3 + CO → (CH3CO)2O
This process involves the conversion of methyl acetate to methyl iodide and an acetate salt. Carbonylation of the methyl iodide in turn affords acetyl
iodide, which reacts with acetate salts or acetic acid to give the product. Rhodium iodide and lithium iodide are employed as catalysts. Because
acetic anhydride is not stable in water, the conversion is conducted under anhydrous conditions. In contrast, the Monsanto acetic acid process, which
also involves a rhodium catalyzed carbonylation of methyl iodide, is at least partially aqueous.
To a decreasing extent, acetic anhydride is also prepared by the reaction of ethenone (ketene) with acetic acid at 45–55 °C and low pressure
(0.05–0.2 bar).[4]
H2C=C=O + CH3COOH → (CH3CO)2O (ΔH = −63 kJ/mol)
Ketene is generated by dehydrating acetic acid at 700–750 °C in the presence of triethyl phosphate as a catalyst or (in Switzerland and the CIS) by
the thermolysis of acetone at 600–700 °C in the presence of carbon disulfide as a catalyst.[4]
CH3COOH H2C=C=O + H2O (ΔH = +147 kJ/mol)
CH3COCH3 → H2C=C=O + CH4
The route from acetic acid to acetic anhydride via ketene was developed by Wacker Chemie in 1922,[5] when the demand for acetic anhydride increased
due to the production of cellulose acetate.
Due to its low cost, acetic anhydride is purchased, not prepared, for use in research laboratories.
From Wikipedia.
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Waffles SS
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Interesting method:
CH3CONH2+CH3COOH+HCl->(CH3CO)2O+NH4Cl
2CH3CONH2+2CH3COOH+H2SO4->2(CH3CO)2O+(NH4)2SO4
[Edited on 28-9-2012 by Waffles SS]
Attachment: Ac2O by HCl.djvu (21kB)
This file has been downloaded 999 times
Attachment: Ac2O by H2SO4.djvu (56kB)
This file has been downloaded 902 times
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Dave Angel
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Interesting? I'd say revolutionary - for the home chemist at least; all components are derived from materials available OTC with cash.
A very nice find, let's hope we can get it to work, I was planning an acetamide synthesis for acetonitrile anyway...
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Waffles SS
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I found it on hyperlab.info website,This is russian patent and unfortunately i cant translate it
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Dave Angel
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I have an old Russian-English technical dictionary hidden away somewhere so I'll see if I can pick out the odd useful word or phrase here and there
when I get a chance.
The H2SO4 patent mentions 'Noyes and Gobel, Americ. Soc. 44, 1922' which is a reference to the method of acetamide production,
described at OrgSyn, and the HCl one makes reference to 130-142° but this could be a boiling range or reaction temperature - who knows?
I'm hoping the percentages in the 90's are yields though 
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manimal
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The sodium pyrosulfate method works in conjunction with calcium propionate to form propionic anhydride, but the reagents must be well-dried (duh).
The following method was attempted: first, sodum bisulfate was heated in an enameled pan over a medium-high flame. It melted and white smoke began to
be evolved after only a few minutes. I found that the bisulfate must be heated strongly for approx. 45 min, during which time smoke evolution is
vigorous, in order for it to lose the theoretical amount of weight required to form pyrosulfate (it wouldn't actually be theoretical, since some of
the weight loss is due to SO3 formation, but it's close enough. SO3 is effective at producing smoke in small quantities, so a little seems like a lot,
and not much is lost).
Commercial calcium propionate was found to be partially hydrated; it was effectively dried by heating in a pan under a medium-low flame, stirring
constantly to prevent charring. It first begins to crackle and pop as it loses water. After the popping stops, the salt is dry. A sample dried in this
manner was heated in a test tube until it melted and began to char and the odor of diethyl ketone became apparent. No water condensation was noted in
the neck of the tube. Weight loss indicated that about half of the commercial propionate was present as the monohydrate.
Sodium pyrosulfate and calcium propionate prepared in this manner were mixed in 1.5:1 molar proportion, respectively, and finely powdered together in
a blender. This was placed in a flask with a condenser set up for reflux, and was heated in an oil bath at 200+C temps for one hour, during which time
there was some liquid condensate visibly dripping back into the flask. Then, the setup was setup for simple distillation and liquid collected for as
long as it would come over. The yield, however, was disappointing: only 15-20%. There is no doubt, however, that the liquid collected contains
propionic anhydride: as was mentioned elsewhere, it has a distinct garlic-like odor. A single drop placed in cold water did not dissolve, but sank to
the bottom as an oily blob. The powder left over in the flask did not look like it had changed much: it was still loose and powdery. A sample was
removed and heated strongly in a test tube, upon which the familiar garlicky odor was detected and condensation appeared on the tube. It appears to be
amenable to the formation of anhydride upon strong heating, but the mixture is very refractory. Oil bath temps do not seem to be high enough to drive
off the anhydride in high yield. I guess that was the point of the diluent proscribed in the patent.
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manimal
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Would the anhydrous acid refluxed in sodium pyrosulfate yield the anhydride?
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ANFO_
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I found an interesting patent on the oxidation of acetaldehyde process, which makes use of paraldehyde and a depolymerizing agent which means the
reaction doesn't have to be performed under pressure to keep the acetaldehyde from evaporating.
http://www.google.com/patents/US2405471
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manimal
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I found that refluxing the pyrosulfate/propionate mixture (prepared as described above) in a sand bath on high heat for 1-2 hours, and then
distilling, gives a more satisfactory yield, around 70-80%  .
There is definitely some subvalent sulfur products forming. A sulfurous stench was apparent during and after the reflux and a yellow deposit formed in
the condenser. A post-distillation rinse in bleach removed most of the odor, but not the yellow stain. Something is reducing the sulfate.
[Edited on 1-11-2012 by manimal]
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jon
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your distilling it to hot i've made that mistake and heated this polluted anhydride under vacum and it cleared up the turbidity too.
Give me librium or give me meth!
Patrick Henry....
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Polesch
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This synthesis might not be very useful, but you can prepare acetic anhydride by distilling a mixture of acethyl chloride and sodium acetate. Anybody
tried this? I did not read the 28 pages before replying.
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mnick12
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Yeah,
The acetyl chloride and sodium acetate method has been mentioned here and quite a few other places, and it does work quite well. I would recommend
mechanical stirring and look out for charring. Honestly though if you have acetyl chloride I do not really see any reason for converting it AA, that
is of course some reaction explicitly calls for it.
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cal
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| Quote: Originally posted by S.C. Wack | As promised, Gmelin. Its enthusiasm is indeed from that JACS article.
Band 61 B5, Seiten 125-6.
2.2.7.2 Thermische Zersetzung
Die Zersetzung von AgCH3COO, die bereits von Chevenix [1] beim Erhitzen über einer Kerzenflamme (starker Geruch nach Essigsäure) beobachtet wurde,
setzt bei 210°C ein (Dunkelfärbung), erfolgt hauptsächlich zwischen 220 und 240°C und ist vollständig bei etwa 300°C [2]. Beim Erhitzen im
offenen Rohr oder im bedeckten Porzellantiegel werden als Zersetzungsprodukte im wesentlichen Essigsäure und Ag neben wenig C02 und C beobachtet
entsprechend 4AgCH3COO ->4Ag + 3CH3COOH + CO2 + C [3 bis 5]. Von Kachler [2] werden als Reaktionsprodukte gefunden (in Gew.-%, nach vorstehender
Gleichung berechnete Werte in Klammern): 64.61 Ag (64.67), etwa 26 bis 27 Essigsäure (26.95), 4.09 bzw. 8.42 CO2 (6.59) und 1.21 C (1.79). Auch bei
thermogravimetrischer Untersuchung wird als Zersetzungsprodukt (bei 280°C) metallisches Ag und kein Ag2O erhalten [6]. Erfolgt die Zersetzung jedoch
unter streng wasserfreien Bedingungen, so werden als Zersetzungsprodukte nur Ag2O und Essigsäureanhydrid erhalten nach 2AgCH3COO -> (CH3CO)2O +
Ag2O. Bei der Zersetzung von 2.1077 g trocknem AgCH3COO bei 300 bis 400°C in einem Quarzgefäß unter Argon (1 atm) werden nahezu quantitativ Ag2O
(96% der Theorie) und Essigsäureanhydrid (93%) gebildet neben wenig Ag (0.012 g) und CO2 (0.016 g) [7]. Die primäre Essigsäureanhydridbildung ist
bereits von Kanewskaja, Schemiakin [8] bei Untersuchung der thermischen Zersetzung von AgCH3COO (im Gemisch mittrocknem Sand) unter einem CO2-Strom
von 20 bis 25 Torr angenommen worden. Zwar fanden diese Autoren nur wenig Essigsäureanhydrid neben viel Essigsäure (entsprechend den früheren
Angaben von Kachler [2] und Iwig, Hecht [4]), doch ist dies auf die leichte Hydratisierung des Essigsäureanhydrids zurückzuführen, die sowohl durch
H2O-Spuren in dem schwer zu trocknenden Silberacetat als auch durch H2O erfolgen kann, das beim teilweisen Zerfall der Essigsäure gebildet wird.
Für die vollständige thermische Zersetzung von AgCH3COO in Gegenwart von H20 muß auf etwa 230 bis 340°C erhitzt werden. Abweichend von der
trocknen Destillation wird neben den Hauptprodukten der Zersetzung Ag, Essigsäure und CO2, kein Kohlenstoff gefunden [2].
Über die Darstellung von Ag-Schwamm durch Erhitzen einer getrockneten Paste von AgCH3COO im Tiegel auf 400 bis 500°C s. [10].
...
[1] R. Chevenix (Ann. Chim. [Paris] 69 [1809] 5/58, 19, 22; Ann. Physik 32 [1809] 156/201, 167, 179). — [2] J. Kachler (Monatsh. Chem. 12 [1891]
338/49, 340). — [3] K. Birnbaum (Ann. Chem. 152 [1869] 111/21, 119). — [4] F. Iwig, 0. Hecht (Ber. Deut. Chem. Ges. 19 [1886] 238/42). — [5] J.
Redtenbacher, J. Liebig (Liebigs Ann. Chem. 38 [1841] 113/40, 131).
[6] D. A. Edwards, R. N. Hayward (Can. J. Chem. 46 [1968] 3443/6). — [7] A. D. Kirschenbaum, A. G. Streng, M. Hauptschein (J. Am. Chem. Soc. 75
[1953] 3141/5, 3143).— [8] S. J. Kanewskaja, M. M. Schemiakin (Ber. Deut Chem. Ges. 69 [1936] 2152/7, 2154). — [9] V. I. Yakerson (Izv. Akad. Nauk
SSSR Otd. Khim. Nauk 1963 1003/11, 1007; Bull. Acad. Sei. USSR Div. Chem. Sci. 1963 914/21, 916). — [10] T. Yamanaka, H. Nidorikawa (Japan.P. 6720
[1956] nach C.A. 1958 10462).
And now, quite possibly pages of off-topic prattle on subjects that have already been discussed elsewhere: |
The decomposition of AgCH3COO, already observed by Chevenix [1] when heated over a candle flame (strong smell of acetic acid) is, at 210 ° C.
(darkening) is mostly between 220 and 240 ° C and is complete at about 300 ° C [2]. When heated in an open tube or in a covered porcelain crucibles
are seen as corresponding to decomposition products mainly acetic acid and Ag next little C02 and C 4AgCH3COO -> 4Ag 3CH3COOH + + CO2 + C [3 to 5].
By Kachler [2] are found as reaction products (in weight -%, calculated according to the above equation in parentheses): 64.61 Ag (64.67), about 26 to
27 acetic acid (26.95), 4.09 and 8:42 CO2 (6.59) and 1.21 C (1.79). Even when thermogravimetric analysis is used as a decomposition product (at 280 °
C) of metallic and no Ag Ag2O obtained. [6] Ie digestion but under strictly anhydrous conditions, so as to be decomposition products only Ag2O and
acetic anhydride according 2AgCH3COO -> (CH 3 CO) 2 O + Ag2O. In the decomposition of 2.1077 g dry AgCH3COO at 300 to 400 ° C in a quartz vessel
under argon (1 atm) almost quantitatively be Ag2O (96% of theory) and acetic anhydride formed (93%) along with a little Ag (0.012 g) and CO2 ( 0016 g)
[7]. The primary Essigsäureanhydridbildung is already Kanewskaja, Schemiakin [8] study on the thermal decomposition of AgCH3COO (mittrocknem mixed
sand) adopted under a CO2 stream of 20 to 25 torr. Although these authors found little besides much acetic acid (according to the earlier information
of Kachler [2] and Iwig, pike [4]), but this is due to the ease of hydration of acetic anhydride, the H2O to both tracks in the hard drying can be
performed as well as silver acetate H2O, which is formed in the partial decomposition of the acetic acid.
For the complete thermal decomposition in the presence of H20 of AgCH3COO must be heated to about 230 to 340 ° C. Notwithstanding the dry
distillation is found next to the main products of the decomposition of Ag, acetic acid and CO2, not carbon [2].
Concerning the presentation of Ag sponge by heating a dried paste of AgCH3COO in the crucible at 400 to 500 ° C, see [10].
...
Thought is an action, which when acted upon becomes work and sometimes art!
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Metacelsus
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Has anyone tried copper(I) acetate? Might it behave the same as silver acetate?
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