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byko3y
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S in halides is a weak electrophile (+1, +2, +4 oxidation state)
S+ + Cl- + OH- + H+ -> SOH + HCl ... + Cl- -> SO + 2HCl
Countrary, it is really stable while in -2 oxidation state.
Acyl group in acyl halide is electrophilic too, this is why it attacks amines. Acyl halides and sulfur halides need a lewis acid to attack
non-activates aromatics. But Cl-S-S-N- is a strong electrophile, this is why it easily attacks activated aromatics. Just like acyl halides can attack
the activated aromatics without a lewis acid, although they prefer to attack O or N group.
Btw, as you may know, there exists a R2N-S-S-NR2 compound and well known R-O-S-S-O-R compounds having sulfur clearly in +1 oxidation state which seems
to be the most stable one.
The idea of a weak electrophile means that sulfur can bind to nucleophiles capable of giving electrons, like alcohols or alkenes do, but not the
carboxylic acids. For this reason you can't make H2S just by pouring a sulfur into acid.
So the Ac-O-S-S-Cl can be barely called pseudohalide. In a regular sulfoxide (R-S(=O)-R) the S-O bound is strongly polarized, and then Ac group is
bound to the oxygen, totaly dividing the molecule into [AcO]- and [S-S-Cl]+.
Let's look at the benzoic acid salt. Unlike the aliphatic acid, this one can relatively easy give away oxygen, providing a [Ar-C=O]+ ion. Or... accept
electrophiles like H+ or S+. Alkenes are also nucleophilic. as you can see in the picture I've posted above (the mechanism of rearrangement of
substituted vinyl alcohol to sulfoxide). And sulfur halides love nucleophiles like alkene (our good old sulfur mustard).
Obviously, acyl group in the sodium acetate is a bad nucleophile, while AcO- is a perfect nucleophile, but! Acyl group of silver acetate is more
nucleophilic! Just like in that of Al(AcO)2OH (acetic anhydride via aluminium acetate proven to work, not by me though and yield is like 30%).
This is the reason why I wanted to read some fresh reasearches on the subject (like that 1970 article) - because in 1913 there were no X-ray
diffractometers, IR, NMR spectrometers, and researches on mass spectrometers were actively conducted.
I really think the active intermediate is not a Ac-O-S-S-O-Ac, but a Ac-SO-S-OAc or even Ac-SO-SO-Ac (the later will probably rearrange to
Ac-SO2-S-Ac). The reason why sodium acetate + sulfur chloride is so hard to perform could be:
- bad nucleophility of acyl group and unability to form a stable sulfoxide, while dithionite is unstable ( [AcO-S(Cl)-S-Cl]- decomposes back to [AcO]-
and S2Cl2, because sulfur is more affine to the chloride then to AcO);
- a need for acetic anhydride either as a catalyst or as a solvent;
- or just a bad solubility of sodium acetate in sulfur halide ^_^ .
Btw, Ph-SO2-S-Ph is a relatively unfavorable product (obtained from (PhSO2)O + PhSH) compared to Me-Ph-SO2-S-Ph-Me (tolyl toluenethiosulfonate) (38%
yield former, 71% yield latter), according to a article "Aromatic Sulfonic Acid Anhydrides" by Lamar Field. Although I don't know which side brings
more stability to the system - both sulfurs have positive oxidation state, so probably both activated aromatics make the product more favorable.
My theory is that decomposition of Ac2O2S2 compound follows intermolecular pathway (some other acyl group is responsible for the formation of acetic
anhydride), as opposed to a high temperature decomposition leading to regeneration of acetate. I doubt that the intermediate could be a Ac-SO-S-Cl,
though this way is possible and thiosulfinates are stable compounds ( https://en.wikipedia.org/wiki/Thiosulfinate ), but the terminal chlorine doesn't look good.
Transition states might be close to Pummerer rearrangement's ones with something like a CH3-C(=S-R)-O-Ac compound.
Quote: Originally posted by clearly_not_atara  | | Well, he's only half wrong. It's generally agreed that S2Br2 converts sulfonic acids to their anhydrides by an unknown mechanism; presumably the
disulfonyloxydisulfide intermediate is too unstable to isolate |
I was not able to find any information on reaction of sulfonates with sulfur halides. Maybe I could try to read some book on the subject? But there is
so few researches of these compounds. And the products of the reaction are unstable, as you and me confirmed, so it might need a catalyst or strong
heating to form them.
| Quote: Originally posted by clearly_not_atara | However of course other reagents exist; cyanuric halides come to mind, as does antimony pentachloride.
What's more interesting to me is I'm still pretty sure the pyrosulfate route will work with methanesulfonic acid (possibly toluenesulfonic acid)
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US8222450 tells about preparing of sulfonic anhdyrides via chlorinated acyl chlorides.
In fact you can mix acetic anhydride with MsHO to get the Ms2O, beacuse this compound can be easily removed from the reaction mixture by distillation,
so there are a plenty of different methods to do this conversion.
[Edited on 25-4-2015 by byko3y]
[Edited on 25-4-2015 by byko3y]
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byko3y
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Okay, I finally found a modern article about dicarboxy disulfide.
Here's a quote of things that seem important to me:
"Thermal Decomposition of Bis(trifluoroacetate) Disulfide.
When (CF3COOS)2 (90.1 mg) was held at 40°C for 12 hr, SO2 (9.8 mg), (CF3CO)2O (65.6 mg), and S (14.7 mg) were obtained after trap-to-trap separation.
Experimental (calculated) percentages of products are: SO2, 10.89 (11.03); S, 16.42 (16.55); (CF3CO)2, 72.59 (71.42), based on the equation
2(CF3COOS)2 ----> 2(CF2CO)2O + SO2 + 3S
Hydrolysis of Bis(trifluoroacetate) Disulfide.
An excess of H2O was condensed onto (CF3COOS)2 (86.3 mg). The hydrolysis products formed [SO2 (9.6 mg), CF3COOH (67.6 mg), and S(14.5 mg)] support the
equation
(CF3COOS)2 + 2H2O ---> 4CF3COOH + SO2 + 3S
.....
Sulfur dichloride with CF3COOAg, C2F5COOAg, C8F7COOAg, or CF3COOH failed to yield the monosulfide analogs, (RfCOO)2S. When these
silver salts were treated with SCl2 in a 2:1 ratio under the same conditions that have been described for the preparation of disulfides (which are
not described in the papar in fact), only SO2, anhydrides, and sometimes traces of perfluoroacyl chlorides were obtained after trap-to-trap or
gas chromatographic (Kel-F no. 3 oil on Chromosorb P) separations. A very exothermic reaction occurred when a 1 : 1 ratio of CF3CO2Ag to SCl2 was
tried. After 30 min, separation yielded CF3COCl (60%) and a trace of (CF3CO)2O, SO2, and SOCl2, as well as an unidentified yellow liquid. The ir
spectrum of the yellow liquid is similar to trifluoroacetic anhydride except for an additional strong peak at 934 cm-l. Work is continuing on this
reaction,
Attempts to break the S-S bond by chlorination of bis(trifluoroacetato) disulfide with chlorine were made. Bis(trifluoroacetato) disulfide and C1, in
the ratios 1.2:1, 1:1.6, and 1:5 were used. After separation of the reaction mixture, the presence of CF3OCl, (CF3CO)2O, SO2, and a trace of CF3Cl was
shown by ir analysis. Unreacted chlorine which remained in all but the first reaction was identified also."
There's another research "Bis(trifluoroaceto) Disulfide (CF3C(O)OSSOC(O)CF3): A HeI Photoelectron Spectroscopy
and Theoretical Study" J. Phys. Chem. A 2006, 110, 5685-5691 but I was not able to retrieve from it any information that would explain more about
chemical properties of the compound.
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Metacelsus
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The attempt to remove an atom from a disulfide bond described in that paper sounds a bit like a procedure I saw in a university lab to convert an
alkyl xanthic disulfide into a thioanhydride. The procedure used triphenylphosphine, I believe.
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clearly_not_atara
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| Quote: Originally posted by byko3y | S in halides is a weak electrophile (+1, +2, +4 oxidation state)
S+ + Cl- + OH- + H+ -> SOH + HCl ... + Cl- -> SO + 2HCl
Countrary, it is really stable while in -2 oxidation state.
Acyl group in acyl halide is electrophilic too, this is why it attacks amines. Acyl halides and sulfur halides need a lewis acid to attack
non-activates aromatics. But Cl-S-S-N- is a strong electrophile, this is why it easily attacks activated aromatics. Just like acyl halides can attack
the activated aromatics without a lewis acid, although they prefer to attack O or N group.
Btw, as you may know, there exists a R2N-S-S-NR2 compound and well known R-O-S-S-O-R compounds having sulfur clearly in +1 oxidation state which seems
to be the most stable one.
The idea of a weak electrophile means that sulfur can bind to nucleophiles capable of giving electrons, like alcohols or alkenes do, but not the
carboxylic acids. For this reason you can't make H2S just by pouring a sulfur into acid.
So the Ac-O-S-S-Cl can be barely called pseudohalide. In a regular sulfoxide (R-S(=O)-R) the S-O bound is strongly polarized, and then Ac group is
bound to the oxygen, totaly dividing the molecule into [AcO]- and [S-S-Cl]+. |
Dude, you can't use poor grammar and abuse of formal oxidation states to argue against numbers. AcO- clearly attacks S2Cl2 in the absence of other
ingredients and in nearly quantitative yield. The fact that you, personally, do not like the way the molecule looks does not in any way constitute
scientific evidence.
Sulfur's preference to bonding with oxygen is a result of the existence of a low covalently-bonded molecular orbital between sulfur and
oxygen with bond order 2. This causes the C-O bond in Ac-O-S to be weaker than in other bond systems. It has nothing to do with the oxidation
state of sulfur in a formal sense.
The reaction must be due to a reaction between S2Cl2 and NaOAc. This either involves formation of the dimer or at least a heterodisulfide
intermediate. And the nucleophilicity data of acetate resp. aniline clearly indicate this is possible.
EDIT: Oh, the other reason silver salts are preferred to isolate the intermediate is that, as before, they dissolve in nonpolar solvents, and so does
S2Cl2.
[Edited on 27-4-2015 by clearly_not_atara]
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Meri
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by heating potassium acetate with benzoyl chloride,yields?synthesis mechanism?can anyone give me some info?
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lochatron
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Simple,mix all ingredients 1:1 distill and vuolia,in good yields
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byko3y
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Meri, it's well known that you can exchange the chloride group of benzoic and aliphatic acids, shifting the equilibrium by distillation. This way you
can distill off the acetyl chloride (b.p. 52 °C), leaving benzoic acid.
I don't think that mixed anhydride is capable of doing the same, until you target compounds is a mixed benzoic-acetic anhydride. In the latter case
the reaction is a regular anhydride synthesis procedure via acyl chloride and carboxylate salt.
UPD: okay, actually sodium acetate is capable of exchanging with benzoyl chloride, this way acetyl chloride is distilled from the reaction mixture.
http://onlinelibrary.wiley.com/doi/10.1002/recl.19891080203/...
"A distillation set up was first thoroughly dried. In a 25-ml round-bottomed flask, 1.9g (23 mol; 1 eq) of sodium acetate and 13.8 g (99 mmol; 4.2 eq)
of benzoyl chloride were heated in an oil bath and then using a naked flame until no further acetyl chloride distilled from the mixture (b.p.
51-53°C). Yield 1.35 g (75%). 1H NMR (100 MHz): 6 2.6 (CH3, s)."
[Edited on 19-7-2015 by byko3y]
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Meri
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Nice one, thank you Byko3y.
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Meri
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you get (acetyl chloride),as well,so way this mechanism is not efficient,nobody talks about this method,becose is low tempetures takes ages or what?
S2Cl2 or other methods is realy not nice for you health.
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2talltman
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I hate to be 'that guy' and not read the entire thread before posting, but I stumbled across this and thought it wouldn't hurt to post it here for
now. I searched the name of the process and nothing came up, so I figure there's a decent chance it hasn't been posted, but that surprises me
considering that it's an industrial route to AA.
It's the Eastman Chemical Company Acetic Anhydride Process.
Attachment: 10.1016@0920-5861(92)80188-s.pdf (980kB)
This file has been downloaded 1619 times
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byko3y
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2talltman, this one is really close to https://en.wikipedia.org/wiki/Monsanto_process , having the same CH3I -> CH3COI intermediate and the same rhodium-iodide catalyst at 50 atm CO
pressure.
The reason why it was not mentioned is because nobody on this board can perform such reactions.
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2talltman
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A few days ago, while delving into the madness that is Wikipedia hyperlinks, I stumbled across something interesting: zinc oxyacetate. Apparently
during its production from zinc acetate, acetic anhydride is formed (albeit in low yields).  I was quite curious.
50 American pennies were dissolved (partially) in 5% white distilled vinegar (a painstakingly long process) and crystallized, then recrystallized into
a white powder, likely zinc acetate dihydrate. 65 grams of this powder were heated under vacuum as the water was driven off, and an unknown liquid
was distilled. The white crystals seemed to burn at first, so the RBF was removed and the crystals stirred, then placed back under vacuum. The
crystals partially melted and released a large amount of vapor, assumed to be H₂O. After this, the crystals darkened slightly to a yellowish color
and began to fume. Throughout the process an odor reminiscent of caramel or heated marshmallows was present, along with the occasional acetate scent.
~10mL of distillate was collected. The liquid had a density of ~1.00g/mL, was clear, yellowish, and smelled of acetate. It had a pH of 2. It did
not combust readily.
However, (and this excites this chemist greatly  ) a portion of the distillate
still in the condenser which had not reached the RBF was found to be much more viscous and greatly irritating to smell, as well as smelling strongly
of acetate and something else which this chemist cannot identify, but not acetone. It did combust readily. When added to water, distortions similar
to those above the road on a hot day appeared (this chemist has forgotten their name). There was not enough liquid to find its density.
To be quite honest, my setup is extremely ghetto. My vacuum source is from an inflatable bed motor, and I'm using an alcohol lamp as a flame source
since I don't have access to the gas lines for a Bunsen burner. I also did not use anhydrous zinc acetate or dry out the condenser after the water
was driven off. If someone were to do this a tad more professionally, then I'm nearly certain good yields of acetic anhydride could be had. I do not
know if the zinc oxyacetate can be regenerated into zinc acetate dihydrate through the addition of acetic acid, but if it cannot, then the zinc
oxyacetate can be combusted to yield ZnO which could then be reacted with the acetic acid to yield the zinc acetate. I also haven't yet found the
mass of the solids left in the RBF, since I know it'll be a bitch to get them out of it.
Attachment: Crystal Structure of Zinc Oxyacetate and Thermal Studies of its Precursor, Zinc Acetate Dihydrate.pdf (671kB)
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Attachment: The Crystal Structure of Zinc Oxyacetate.pdf (3.9MB)
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Edit:
Thanks for that, I wasn't really thinking, I guess.
On an unrelated note, I wasn't even attempting to find acetic anhydride syntheses when I stumbled across these two. Wikipedia is just amazing like
that.
[Edited on 13-8-2015 by 2talltman]
Update: The alcohol left a whole bunch of carbon on the bottom of the RBF, which I got on my hands as I was about to clean it. I removed the
thermometer from my distillation setup and smelled a bit of the condensation on it. It burned my nose absolutely terribly, making me even more
confident that this is a viable route to acetic anhydride. But, carbon on hands + burning nose --> one funny looking guy. On the bright side, the
mass was quite easily removed from the RBF with a little bit of 91% isopropanol. I could vacuum dry it and find its mass if anyone is interested.
[Edited on 13-8-2015 by 2talltman]
Edit #3:
Welp, editing for the third time I see that this synthesis was posted earlier in the thread. Sorry, I promise I searched for it!  It just didn't come up for me. Oh well, experimental evidence never hurt anybody.
[Edited on 14-8-2015 by 2talltman]
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byko3y
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2talltman, I can't understand what are your products, because you give not temperatures. Most common way to determine whether you've got anhydride or
not is to react it with amine to form amide. No other product at r.t can do the same. Ammonia is not liquid and usually stored as solution in water,
so aniline is the most common reagent for the purpose. Acetanilide has m.p. of 114.3 °C
Aluminium acetate is also known to decompose into acetic anhydride. Yield is declared to be 30% (although you can use only 2 of 3 acetate molecules,
so it's 45%). I'm pretty sure the mechanism is ketene formation, obviously, the yield is low because of poor balance and different side reactions
comparing to industrial ketene process with dedicated acetic acid -> ketene reactor operating at 700-750◦C.
[Edited on 14-8-2015 by byko3y]
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2talltman
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Most of the liquid distilled over at ~90°C under vacuum, but the temperature went up to 97°. I have such a limited lab that I basically don't have
one, so I can't test the distillate with acetanilide. I would love for someone else to do so, though.
If it does in fact go through ketene, wouldn't that be exceptionally dangerous? The idea of it really freaked me out last night, so I quenched
everything with water and sprayed water into the air, as well. Here's hoping I wasn't exposed to anything. From the data I read, death usually
occurred within 12 hours, so I'm thinking I'll be okay.
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Meri
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yes
[Edited on 16-8-2015 by Meri]
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clearly_not_atara
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It's probably a concerted mechanism, but even if ketene were an intermediate I wouldn't worry that much. Ketene has to be produced in some quantity
for there to be a concern; it should immediately react with acetate. It's much more unstable than cyanide or phosgene or even SOCl2 for that matter.
After all if a significant amount of ketene were produced, 2tallman would already be dead...
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clearly_not_atara
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Can't edit ^^ anymore, but I found a ref that says that anhydride is produced from Zn(OAc)2, but the acetate and oxyacetate are molecular
(hence volatile) and will also vaporize under vacuum. Ideal conditions were a low heating rate in a nitrogen atmosphere.
So 2tallman's route is not just some Wikipedia citogenesis.
Attachment: actaznoacanhydride.pdf (1.8MB)
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Waffles SS
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Anhydride from acetates mentioned some pages ago.
I got anhydride from silver acetate by this route and this is possible for aluminium ,zinc and copper too.(you can find my post about it)
There is no need to use aniline for testing anhydrid,A single drop placed in cold water did not dissolve, but sank to the bottom as an oily blob
Read page 28
[Edited on 21-8-2015 by Waffles SS]
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CuReUS
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it seems ethylidene diacetate on heating decomposes to give acetaldehyde and acetic anhydride. Although the diacetate is quite expensive,it can be
made from acetylene and acetic acid in the presence of mercuric sulphate catalyst.
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Waffles SS
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Ethylidenediacetate method is my suggested method.this method is cheap and easy.just require acetic acid,acetylene and small amount of mercuric
catalyst.recommended catalysts are mercury(II( salt of disulfonic acids like methandisulfonic acid(methionic acid),benzenedisulfonic acid and other
disulfonic acids.By using this type of catalysts tar formation decrease and yield increase.
I usually make my Ac2O by this method(just vinyl acetate instead of acetylene)
More information about this method on page 28.
I attach useful review about making ethyidenediacetate and vinyl acetate
Attachment: morrison1933.pdf (1MB)
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[Edited on 21-8-2015 by Waffles SS]
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clearly_not_atara
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With all due respect, there doesn't seem to have been a mention of Zn(OAc)2 on 28; Ctrl+F
"zinc" and "zn" both find nothing. In any case hopefully the paper is useful.
[Edited on 22-8-2015 by clearly_not_atara]
[Edited on 22-8-2015 by clearly_not_atara]
[Edited on 22-8-2015 by clearly_not_atara]
[Edited on 22-8-2015 by clearly_not_atara]
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Waffles SS
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on page 28 you can read about pyrolysis of silver acetate and copper acetate
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Waffles SS
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Reaxys search of all possible way for synthesis Acetic anhydride
Attachment: Acetic anhydride.pdf (2MB)
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brew
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I'm pretty sure that if the following was possible, it would be in the literature. Yet I cannot help wonder because if the inclusion of a dehydration
reagent can work for eg, acetic acid to go on to form the anhydride, well its clear that a 1,2, addition has occurred, and water being eliminated, and
soaked up with say phosphorous pentoxide, hence I'm wondering if a small amount of acid catalyst (98% H2SO4) was added to say, acetic acid, and
utilizing toluene, under DS trap conditions, as no azetrope forms between acetic acid and water I think, but does very well with toluene and water.
b.p, around 80 odd C, and when it cools down in the trap, they are obviously are going to separate. Perhaps with the inclusion of another reagent that
mops up water would quicken this up. As said, Im sure that if this was a given, it would be known, but its had me wondering, and hopefully I have
some facts correct, and of course experiment is king.
If this is utter nonsense, and Ive not got my facts straight, then my apologies, but thought an amateur chem forum is the sort of forum that ideas,
albeit nonsense ones, can at least be expressed.
Im also not interested in the product, but its more about novel ways to get to these reagents that I find the challenge.
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clearly_not_atara
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The energetics of the reaction: Ac2O + H2O >> 2AcOH are such that it might as well be considered irreversible. As such trying to use Le
Chàtelier's principle probably won't work. Effective methods all rely on generating some low-energy byproduct, be it SO2, Ag2O, Zn4O(OAc)6, etc.
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