Sciencemadness Discussion Board

Acetic anhydride preparation

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LSD25 - 14-6-2008 at 19:56

Well it depends upon whether the reaction could be undertaken below the boiling point of MsCl doesn't it?

In that respect, this article might be of some, slight interest:
Quote:
J. Org. Chem., 62 (11), 3552 -3561 jo960441u S0022-3263(96)00441-0
Copyright © 1997 by the American Chemical Society

DOI: 10.1021/jo960441u

Mechanism of Polyphosphoric Acid and Phosphorus Pentoxide-Methanesulfonic Acid as Synthetic Reagents for Benzoxazole Formation

Ying-Hung So* and Jerry P. Heeschen

Central Research & Development, 1712 Building, The Dow Chemical Company, Midland, Michigan 48674

Received: March 4, 1996

Abstract:

The mechanism of 2-phenylbenzoxazole formation from benzoic acid and o-aminophenol in polyphosphoric acid (PPA) is studied by NMR spectroscopy and chemical analysis. Benzoic acid reacts with PPA to form benzoic-phosphoric anhydride and benzoic-polyphosphoric anhydride. The ratio of mixed anhydride to free carboxylic acid increases dramatically as the P2O5 content of PPA increases, but this ratio is independent of reaction temperature and time. When o-aminophenol dissolves in PPA, part of the hydroxyl group is converted to phosphate ester, and only protonated amine is detected. Benzoic acid, mixed anhydride, and PPA are in dynamic equilibrium, and so are PPA, o-aminophenol, and its phosphate ester. The mixed anhydride and o-aminophenol react to form 2-aminophenyl benzoate as the first reaction intermediate which undergoes rapid acyl migration to generate 2-hydroxybenzanilide. Ring closure of 2-hydroxybenzanilide to form 2-phenylbenzoxazole is acid catalyzed. The reactive components in phosphorus pentoxide-methanesulfonic acid (P2O5-MSA) which is a convenient alternative to PPA are very similar to those present in PPA. Benzoic acid is also converted into mixed anhydride in P2O5-MSA.


Seems to me that if the benzoic acid forms a mixed anhydride, that addition of the sodium benzoate (or sodium carbonate) should be sufficient to give the benzoic anhydride, which gives access to a classic route to many aliphatic anhydrides. Alternatively, it would be very interesting to see if the acetic/propionic anhydrides could be formed in-situ when reacted with the P2O5-MSA mixed anhydride, wouldn't it?

Sauron - 14-6-2008 at 20:52

Far, far easier and simpler and more promising to replicate the tosyl chloride method - which you get the credit for digging up, not me.

Mesyl chloride seems like a lot more trouble.

Its sole virtue being that DMSO is cheap. I would argue that anyone who can get DMSO can get tosyl (p-toluenesulfonyl) chloride.

If the object of the exercise is to have fun exploring the MsCl prep and route to acetic anhydride, then by all means, enjoy yourself.

I rather thought the point was pretty much to get to Ac2O by the most accessible and convenient means possible.

Dry NaOAc + TsCl sans solvent looks like that to me.

Cheaper than the oxalyl chloride route

Simpler than NaOAc + S + Br2 (or a preformed sulfur halide)

Simpler than the fiddly and hazardous ketene process.

Does not require AcCl (maybe it forms that in situ?)

You really can't get much simpler than a melt of two solids to make a liquid than promptly boils off to be condensed. No solvent, one pot, isolation accomplished. TsCl is not a suspicious chemical at all. Neither is sodium acetate.

All that is left is to actually try it.

As to NaOAc, I have a Kg of commercial anhydrous Merck, never opened. I also have a thermostated forced air drying oven that goes to 250 C and a 12" evaporating dish. The oven is by Memmert. I bought it new.

LSD25 - 14-6-2008 at 22:22

Yeah, I do like the look of the TsCl route - it has some serious benefits - but although I can get DMSO, but not TsCl (I could make it, but that ain't trivial) it probably is beyond my means.

The use of simple polyphosphoric acid (once again, monoammonium phosphate + heat = polyphosphoric acid + ammonia) and benzoic acid to form the mixed PPA-Benzoic anhydride should, maybe with additional sodium benzoate, give the benzoic anhydride which would be simpler than even the MsCl route - especially given that benzoate salts and the monoammonium phosphate (the fertilizer grade variety is coated with an organic grease and contains about 50% inert, insoluble material, the bit you want is highly soluble in water) are cheap and easily sourced.

What would be interesting is to try the PPA/phosphoric anhydride route to AA through GAA & NaOAc, that would truly be cheap, simple and scaleable.

But if one added benzoic anhydride to GAA, surely there would be AA produced (the converse of adding AA to benzoic acid to produce benzoic anhydride: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv1...)

PS For those who have p-toluenesulfonic acid or who are using there TsCl and don't want to buy more in order to do it again, the attached material might be of interest

{EDIT}

Bloody thing didn't attach, here goes again

[Edited on 14-6-2008 by LSD25]

Attachment: TsOHtoTsBr.pdf (80kB)
This file has been downloaded 1953 times

Sauron - 15-6-2008 at 00:00

If one has access to bromine then the Russian method (in situ generation of sulfur bromide and reaction with anhydr NaOAc) opens up. The intermediate decomposes on mild heating to Ac2O.

This is fully described upthread.

Benzoic anhydride is commercially available is it not? Simple enough therefore to see if the reactions you propose have merit.

Len 1 has spent a lot of time and effort demonstrating how SO3 can be made, so has garage chemist. If you have SO3 or oleum (fuming H2SO4) and can generate dry HCl you have the means to make chlorosulfonic acid. If you have chlorosulfonic acid and toluene you have all you need to prepare TsCl. I think it is more trouble than $45 a Kg is worth, but that's just me. I don't know of any simple way to chlorinate TsOH to TsCl. AFAIK the chloride is always prepared from toluene and chlorosulfonic acid.

Sauron - 15-6-2008 at 17:51

I am having problems constructing an equation or equations for the reaction of p-toluenesulfonyl chloride and anhydr. sodium acetate to form acetic anhydride.

This reaction is reported in JACS as proceeding in high yield (90%) with equimolar amounts of reactants on a 22 mmol scale, without solvent, and with heating to 180-200 C for 30 minutes.

The TsCl will be liquid at such temp. Sodium acetate will presumably dissolve or be suspended in the melt; anhydrous NaOAc decomposes at >300 C, but this is well above the reaction temperature. TsCl boils at 324 C/10 mm Hg, so again the reaction temperature suggests no obvious decomposition.

I would prefer to understand the reaction better before trying it. Is HCl produced? What is left in the pot? I would guess, NaCl and p-toluenesulfonic acid (TsOH) but initial attempts to write an equation along the lines of

2 TsCl + 2 NaOAc -> (MeCO)O + 2 TsOH + 2 NaCl

fail to balance.

Sodium tosylate is a possible product. But that leaves us with chlorine. Is the tosyl chloride merely catalytic? If so what happens to the sodium?

Does a mixed anhydride of p-toluenesulfonic acid and acetic acid form as an intermediate?

I don't recall ever hearing of anhydrides of arylsulfonic acids..

At the moment I am suffering from Chemrox Syndrome, a severe head cold, and cannot think.

HELP!

[Edited on 16-6-2008 by Sauron]

Klute - 15-6-2008 at 18:18

Aliced25, that article sued toluenesulfinic to form the tosyl bromide, not the sulfonate unfortuanly.

EDIT: apparently, a mixed anhydride is forme din this reaction, not the acyl chloride:
Quote:

Synthesis 2004: 205-207
DOI: 10.1055/s-2003-44381


A Cheap, Simple and Efficient Method for the Preparation of Symmetrical Carboxylic Acid Anhydrides

Foad Kazemia, Hashem Sharghi*b, Mohammad Ali Nasserib
a Department of Chemistry, College of Sciences, Chamran University, Ahvaz, I. R. Iran
b Department of Chemistry, College of Sciences, Shiraz University, Shiraz, 71454, I. R. Iran
Fax: +98(711)2286008; Email: shashem@chem.susc.ac.ir;
Received 13 October 2003
Abstract

A manipulatively simple and facile one-pot procedure for the synthesis of symmetrical anhydride is reported. Treatment of carboxylic acids with tosyl chloride in K2CO3 media under solvent free conditions gives the corresponding anhydrides in good to excellent yields in a short reaction time via carboxylic sulfonic anhydride as the key intermediate.


Howeevr, I have seen several procedure using TsCl to form acyl chlorides, so I was pretty sure the reaction goes through acetyl chloride.

TsCl can be produced from TsOh by reacting with chlorosulfonic acid, which is pretty irrevelant here. Chlorination of TsOH leads to ring-chlorinated products (US 4131619)


Found this:

US patent 4696774
Quote:


In Yet another method, arylsulfonic acid is reacted with a sulfur monohalide in the presence of excess halogen. This latter method is especially useful in the production of benzenesulfonyl chloride wherein benzenesulfonic acid, sulfur monochloride and chlorine are reacted to produce benzenesulfonyl chloride. In this process described immediately above, the arylsulfonyl halides produced can be removed by distillation from the reaction mixture.
However, the distilled arylsulfonyl halide product is usually discolored by the presence of impurities and can be almost black in color. It would be advantageous from a customer's viewpoint to treat the arylsulfonyl halide with various decolorizing agents to achieve a pale yellow to colorless product of higher purity.



EXAMPLES

This experiment illustrates an improved process for producing
benzenesulfonyl chloride that can be decolorized by the process of this
invention.


To a 1 liter flask was added 808 grams (5.1 moles) of benzenesulfonic acid and 5.7 grams of a 70 percent solution of phosphorous acid (4.0 grams phosphorous acid/1.7 grams water). Sulfur monochloride addition was started and after all the sulfur monochloride had been added, chlorine was
bubbled into the reaction mixture for a period of 20 hours at 80°C. The resultant benzenesulfonyl chloride was removed by distillation.



This seems like themost convienient way of preparing sulfonyl chloride fromaromatic sulfonic acids. Aromatic sulfonyl chlorides cannot be prepared by chlorination of sulfur compounds such as thiosulfates, disulfides, thiols, etc.

The reaction could be done in one pot, preparing the S2Cl2 by chlorinating sulfur, adding the sulfonic acid once most of the sulfur has reacted, and continuing chlorination. The sulfonyl chloride can then be isolated and purified as mentionned in the patent.

Although this would be tedious just o obtain Ac2O (just aswell use S2Cl2 with AcONa!) It si a good way of obtaining aromati csulfonyl chlorides for other purposes, even though this is drifting off topic.

[Edited on 16-6-2008 by Klute]

Sauron - 15-6-2008 at 18:57

Carboxylic acid plus potassium carbonate will give the potassium carboxylate, and that reacts with the TsCl. I would not expect the carboxylic acid to have the pKa to dislodge TsOH from potassium tosylate if that formed first. Anyway thanks for the reference. I have Synthesis on CD so it won't take long to read.

Klute - 15-6-2008 at 19:15

What I fail to understand, is how, by adding K2CO3 to an acid medium, and thus producing H2O, one can obtain an anhydride?! Why not use a preformed, dried potassium salt? I guess I need to read the protocole before guessing anything...

S.C. Wack - 15-6-2008 at 19:36

Quote:
Originally posted by Sauron
I am having problems constructing an equation or equations for the reaction of p-toluenesulfonyl chloride and anhydr. sodium acetate to form acetic anhydride.


DE123052 equations. Add a CH3 as these are illustrated for benzenesulfonyl chloride, though only 1 of the 5 examples uses it, the others using p-toluenesulfonyl chloride.

Hadn't mentioned the patent before because if you can make or buy these chlorides, then you shouldn't have any problem making or buying acetyl chloride or acetic anhydride in the first place.

EDIT: If the pdf does not display in your browser, it is due to your Acrobat or browser settings. Use the "save full document" feature to save the patent.

[Edited on 15-6-2008 by S.C. Wack]

Sauron - 16-6-2008 at 02:40

Unfortunately the Iranian-authored paper from Synthesis (attached below) dies not apply to the lower aliphatic carboxylic acids, as the requirement is that the anhydride produced not be moisture sensitive.

That certainly does not apply to acetic anhydride.

In their procedure, the (solid) carboxylic acid and potassium carbonate are mixed in a mortar with grinding. TsCl moistoned with EtOAc is then added in small portions and the mixture ground for a specified period.

[Edited on 16-6-2008 by Sauron]

Attachment: anhydrides.pdf.pdf (45kB)
This file has been downloaded 4888 times

Sauron - 16-6-2008 at 08:59

The German patent cited by S.C.Wack does come to the point. It teaches that one equivalent of TsCl and anhydr NaOAc react to form AcCl and NaOTs, while one equivalent of TsCl and 2 equiv of NaOAc give one equivalent each of Ac2), NaOTs and NaCl.

It is well accepted that in the latter case AcCl forms first as per the first reaction, and then the AcCl reacts with the second equivalent of acetate salt to form the anhydride.

I am perfectly comfortable with this explanation. However, it forces me to go redo my calculations of the reaction from the JACS article I cited, which taught that equimolar amounts of TsCl and dry NaOAc (4.25 g and 1.62 g respectively, 22 mmol) gave 10 mmol Ac2O. rather than AcCl. (0.95 ml).

I rechecked my calculations.

The JACS article prepared sodium acetate from 3.7 g silver acetate, which is 22.2 mmol, so 1.82 g anhydrous sodium acetate. They heated this with 4.25 g TsCl, also 22.2 mmol.

Product 0.95 ml acetic anhydride, 10 mmol (about 1.06 g).

So my aithmetic is good, but we are left with this little anomaly.

Per the German patent why is this Ac2O and not AcCl?

[Edited on 17-6-2008 by Sauron]

Klute - 16-6-2008 at 13:12

Well, i guess if you add another equivalent of AcONa, Ac2O will be formed?
In the preparation of AcCl, there is no excess acetate to react, while the patent yes? (I haven't read it, don't undersatnd german).

Sauron - 16-6-2008 at 17:57

Better to read it, or at least read the equations.

The same two steo process is also to be found in many other textx and publications and with a variety of chlorinating agents.

Step 1: the chlorinating agent (generally an acid chloride) reacts with the anhydrous NaOAc to form AcCl and the salt of the acid.

Step 2:

The AcCl reacts with more NaOAc to yield acetic anhydride.

This can be run as discrete steps with isolation of products.

The OVERALL reaction is (for tosyl chloride)

2 NaOAc + TsCl -> (AcO)2O + NaCl + NaOTs

If you go look at Roger Adams in JACS on oxalyl chloride as reagent for acyl chlorides and anhydrides you will see the same reactions and dtoichiometry, the major difference being that oaxalyl chloride falls apart to CO and CO2 and leaves less mess behind. Just NaCl.

I think I had better look at the Iranian paper again. I just did so and they employed 2 equivalents carboxylic acid to 1 of TsCl.
So the same stoichiometry prevails, the Iranians just propose a mixed anhydride mechanism in lieu of the classical one.

Anyway it is simple enough to try the JACS procedure both ways (with 1 equivalent, and with 2 equivalents.) If the first gives AcCl and the second Ac2O, fine. If both give Ac2O, also fine, from a preparative point of view.

In order to explain the result obtained in the JACS article, where equimolar amounts of TsCl and NaOAc are used, we would have to hypothesize that the formation of AcCl is slower than the reaction of AcCl with NaOAc to form the anhydride. Therefore only half the TsCl present reacts with NaOAc, because as soon as it does the AcCl formed consumes the remaining NaOAc to form Ac2O in the amount of half the equivalent of NaOAc present.

If the equimolar reaction produced Ac2O as reported and not AcCl, then half of the TsCl should remain unreacted in the post, while all NaOAc has been consumed leaving NaCl and NaOTs in equal amounts (roughly).

Since the authors are mum about such details we are left to try this experimentally.

Note the bp's. The reaction is run at 180-200 C. Ac2O boils at 140, acetyl chloride IIRC at 54 C. Therefore the reaction of acetyl chloride to form Ac2O MUST be instantaneous or AcCl will flash off at almost 3X its boiling point.

[Edited on 17-6-2008 by Sauron]

Sauron - 17-6-2008 at 18:58

Another possible, is far fetched explanation: human error.

In that JACS paper, which was after all not about this reaction but instead just using it in passing as part of an isotopic labelling procedure, the "acetic anhydride" produced, all 0.95 ml of it, was used directly in a Friedel Crafts acylation of benzene with AlCl3 to make acetophenone.

So it occurs to me that for their purpose acetyl chloride would have produced exactly the same result. So perhaps they simply misreported the intermediate as Ac2O when in fact it was AcCl.

------------

It is noteworthy that the German patent teached running the reaction at the bp of Ac2O (140 C) and collecting the Ac2O at reduced pressure.

[Edited on 18-6-2008 by Sauron]

Engager - 24-8-2008 at 17:56

I have fair ammount of thionyl chloride and sodium acetate, somebody has actual synthesis procedure for making Ac2O from this reagents?

Klute - 24-8-2008 at 18:43

As Vogel's explains, thionyl chloride can't be used for preparing AcCl as the bp of AcCl and SOCl2 are too close to acheive a good seperation.

But, it could perhaps be possibly to react SOCL2 with 2-3eq of rigorously dried AcONa to form AcCl which reacts with more AcONa to form the anhydride, which could then be fractionnated from any unreacted SOCl2.

I'm not sure if the sodium salt will form the acyl chloride, or if the acid is needed. In that case, reacting AcOH and SOCl2 in a first step, then adding anhydrous AcONa, and fractionnating after some reflux could work. The thing is SOCl2 is usually used in excess, so if using stoechiometric amounts, you might have some unreacted SOCl2 in the soup.

It's hard to give a defiante answer. Try it out on a small scale?

Sauron - 24-8-2008 at 23:26

We have enumerated many ways in which NaOAc (anhydrous) can be used to prepare AcCl and/or Ac2O. I seriously doubt that SOCl2 is another one.

SOCl2 fails about as often as it succeeds.

As noted acetic through butyric acids are too close (as their acyl chlorides) to the bp of SOCl2 to seperate, cf. Vogel.

Trichloroacetic acid fails with SOCl2.

Oxalic acid (anhydrous) fails with 2 equ. SOCl2.

Malonic acid succeeds to extent of 60% yield.

Succinic and glutaric acids form only the cyclic anhydrides with SOCl2 not the acid dichlorides.

Same for phthalic acid.

So despite its vaunted reputation SOCl2 is a sometimes thing.

See attached study of the scope of reaction of thionyl chloride on a wide variety of carboxylic acids.

[Edited on 25-8-2008 by Sauron]

Attachment: JAmChemSoc1928p145.pdf (311kB)
This file has been downloaded 1882 times

Engager - 25-8-2008 at 05:35

Thanks for the reference but it is not what i'm looking for, i need detailed procedure on preparation of acetic anhydride from thionyl chloride and sodium acetate. In theory it seems easy:

2CH3COONa + SOCl2 => (CH3CO)2O + SO2 + 2NaCl

Any impurities such as acetyl chloride and unreacted SOCl2, should be easy to separate taking to account their low boiling ponts. However i'm looking for data about reaction conditions, and any problems that could be related with this synth. That's why i need exact synth procedure for this case.

Sauron - 25-8-2008 at 05:50

How can I or anyone else give you procedures for a hypothetical reaction that in my opinion will not work?

Sodium acetate (properly dried, not a trivial task) reacts with acetyl chloride to produce acetic anhydride.

Sulfur, bromine and anhydrous sodium acetate interact and on mild thermolysis release Ac2O.

Acetic acid or anhydrous sodium acetate react with oxalyl chloride to give acetyl chloride or acetic anhydride, depending on rations of reagents. Oxalyl chloride is expensive and the yields are not very good.

Acetic acid and cyanuric chloride react in acetone in presence of triethylamine to give acetyl chloride, which once isolated, reacts with anhydrous NaOAc to give Ac2O.

Ketene and acetic acid give acetic anhydride. Ketene is toxic (very).

If you have SOCl2, use it to make AcCl and react that with NaOAc anhydrous. Reacting SOCl2 with NaOAC is IMO a waste of reagents and time. SOCl2 only gives anhydrides of carboxylic acid in a few cases invariably involving dicarboxylic acids that can form a 5 or 6 membered cyclic anhydride. Acetic anhydride is not one of these.

Engager - 25-8-2008 at 06:44

Quote:
Originally posted by Sauron
How can I or anyone else give you procedures for a hypothetical reaction that in my opinion will not work?


This reaction actualy work, and that is mentioned in patents and literature, for example russian chemical dictonary present reaction of thionylchloride with glacial acetic acid as one of methods for preparation of acetic anhydride (as well as SO2Cl2 and PCl3). So there is no question is it working - simply it is, but about exact reaction conditions.

[Edited on 25-8-2008 by Engager]

Formatik - 25-8-2008 at 07:49

Engager, acetic anhydride can be made by adding SOCl2 to boiling glacial acetic acid using a reflux condenser which is held at -15 to -20ºC, see: DE 396696, DE 411519. The yield was 81% with SOCl2 in example from the first patent, with pure chloride giving a much higher yield.

Sauron - 25-8-2008 at 09:03

Put not your faith in patents!

Do these patents cite any references to the primary literature that can be examined and evaluated?

That is where you will either find preperative details, or nowhere.

Failing that all you can do is experiment on your own but IMO you are chasing a phantom reaction.

SO2Cl2 will not make Ac2O and neither will PCl3.

The SOCl2 and PCl3 will make AcCl and then you will not be able to cleanly seperate the mixture. If you do not believe me, try it yourself.

A modern chemistry book referenced an old paper, saying that dry distillation of anhydrous NaOAc and cyanuric chloride gave AcCl. So I dug out the old paper. The statement was true. But they neglected to mention the yield was 5%.

The devil is always lurking in the details.

[Edited on 26-8-2008 by Sauron]

Formatik - 25-8-2008 at 12:07

Quote:
Originally posted by Sauron
Put not your faith in patents!

Do these patents cite any references to the primary literature that can be examined and evaluated?


No, but when talking of AcCl or SOCl2 with GAA, Beilstein also cites: Centralblatt 1924 II, 1401; 1925 II, 92; Frdl. 14, 254, 1484. The last is a collection of patents, but Centralblatt is pretty basic.

Sauron - 25-8-2008 at 12:32

Centralblatt is the German predecessor to Chemical Abstracts. So the question is what was Centralblatt citing? Primary literature that can be obtained in full text? Patents? What?

Engager's postulate is about NaOAc and SOCl2.

Any method to generate AcCl that works, is fine. I say isolate the AcCl and then have your pick of its reactions to make Ac2). We have an embarassment of choice as to how to make AcCl. Make it. Purify it. Then use it.

Look at it this way: SOCl2 is at times a chlorinating agent and at times a dehydrating agent. Is it dehydrating AcOH to Ac2O? No. It is chlorinating AcOH to AcCl. Period, end of story for SOCl2, it is gone as SO2 and HCl.

AcOH +SOCl2 -> AcCl + SO2 + HCl

Now with excess AcOH, the AcCl formed in first step reacts:

AcCl + AcOH -> Ac2O + HCl.

And you distill the Ac2O out of AcOH excess remaining. All byproducts are gaseous.

What happens with oxalyl chloride is quite different.

oxalyl chloride and 2 mols of a monocarboxylic acid form 2 HCl and a double anhydride which falls apart to the simple anhydride + CO + CO2.

Per Adams:

2 RCOOH + (COCl)2 -> (RCOOCO)2 + 2 HCl
(RCOOCO)2 -> (RCO)2) + CO + CO2

Adams says this is experimentally verified and many of the double anhydrides have been isolated.

The two equations can be unified as

2 RCOOH + (COCl)2 -> (RCO)2O + 2 HCl + CO + CO2

If you want the acyl chloride you must react the anhydride with more oxalyl chloride.

If instead of AcOH, NaOAc is used, the reaction proceeds as follows:

Equimolar ratios give AcCl and NaCl and CO and CO2

MeCOONa + (COCl)2 -> MeCOCl + CO + CO2 + NaCl

If 2 mols NaOAc are used per mol oxalyl chloride

2 MeCOONa + (COCl)2 -> (MeCO)2O + CO + CO2 + 2 NaClUnfortunately I don't see how this sheds any light on the reactions of SOCl2 with acetic acid or NaOAc.

For anhydride to form, the molar ration would be 2 acid to 1 SOCl2

2 RCOOH + SOCl2 -> (RCO)2O + SO2 + 2 HCl

Does this occur? Not one word in the JACS paper on SOCl2 rxns w/carboxylic acids.

AFAZIK it only occurs when CYCLIC anhydrides of DIBASIC acid are involved and the rings formed are 5 or 6 membered.

Succinic, glutaric, maleic and phthalic acids react this way with SOCl2. BUT NOT MONOCARBOXYLIC ACIDS.

Obviously the stoichiometry for attempted prep of a acyl duchloride requires twice as much SOCl2

HOOCCH2CH2COOH + 2 SOCl2 -> Succinic anhydride + 2 HCl + SO2 + 1 SOCl2 unreacted

That is, even if you use enough SOCl2 to make succinyl chloride, all you will get is succinic anhydride, by abstraction of one mol H2O, and 1 mol SOCl2 unreacted.

It is possible to force the chlorination in some cases per KIyrides by use of catalyst ZnCl2, to give phthalyl chloride from phthalic acid or anhydride for example.

I know of no catalyst for drive SOCl2 to make acyclic acid anhydrides.

Adams says the oxalyl chloride reaction works better with sodium salts of carboxylic acids than with the free acids.

We can hope the same is true for SOCl2 but we can't surmise it with so little basis in the literature. Not unless and until we test experimentally.

Let's work out the stoichiometry first.

NaOAc + SOCl2 -> AcCl + SO2 + NaCl

2 NaOOCMe + SOCl2 -> (MeCO)2O + SO2 + 2NaCl

At least those balance. I would suggest doing this in toluene as solvent. Warm the mixture till no more SO2 comes off. You should have a ppt of NaCl. Filter it off. Now distill the product from the solvent. A good column and you will be able to tell what you have by bp.

If NaOAc is not dry all you do is make SO2 and HCl reducing the effective amount of SOCl2.







[Edited on 26-8-2008 by Sauron]

[Edited on 26-8-2008 by Sauron]

Engager - 26-8-2008 at 05:35

Preparation of Ac2O from thionylchloride was successful, here is description of my experiment:

120 ml of glacial acetic acid was added to 144 ml of thionylchloride, reaction takes place on mixing, leading to formation of HCl+SO2 and mixture is strongly cooled (endotermic reaction). Mixture is allowed to stand at room temperature for 2 hours, allowing most of HCl and SO2 to evolve. Next, reaction mixture is placed on water bath under efficent reflux condenser, tubing was tightly attached to end of condenser to vent reaction gasses to outside, bath was heated to 55C and mixture is left at this temperature for 2 hours. During this period convertion of acetic acid to acetylchloride is fully completed, and gas evolution ceases. Reaction product was cooled to room temperature and then in ice bath, 160g of freshly melted pulverized sodium acetate was added with stirring. Addition rate is adjusted, to not allow reaction mixture to boil. After acetate is added mixture is allowed to stand for 30 minutes at room temperature and was destilled. All liquid phase from reaction mixture is distilled off in temperature interval about 4C (about 136-140C), about 200 ml of distillate is obtained witch is acetic anhydride. Yield was not precisely mesasured but it is close to that predicted by theory. Reaction equations:

SOCl2 + CH3COOH => CH3COCl + HCl + SO2
СH3COCl + CH3COONa => (CH3CO)2O + NaCl

[Edited on 26-8-2008 by Engager]

Sauron - 26-8-2008 at 06:30

Excellent! That is a good conservative way to do it. It does rather leave Vogel standing in the corner wearing a pointy hat, doesn't it?

Do you have enough SOCl2 left to try to react it directly with dry NaOAc to see if Ac2O can be had that way as well?

Klute - 26-8-2008 at 06:38

Congratulations! excellent work!

Now this is the way of concluding on a reaction working or not. Sauron gave a very detailed theoretic description, very interesting, but your experimental work gave irrecovable results.

I only wish more people acted like you, Engager, trying out experiemntal work even if details are lacking in the litterature. It seems alot of people are too reticient to "waste" their reagents unless there is a very detailed, established procedure.

Thanks for sharing. I'm sure many will appreciate

Sauron - 26-8-2008 at 06:58

There was no doubt that SOCl2 and AcOH would yield AcCl; Vogel and others merely quibbled about the difficulties of isolating the AcCl in pure form - especially in the days when SOCl2 was usually contaminated with various P and S compounds.

And there was no reason to doubt that AcCl would react with anhydrous NaOAc. Various people have done a lot of pissing and moaning about the chore of fusing the trihydrated acetate twice and losses particularly in the second fusion.

I have always argued for buying the best grade of anhydrous sodium acetate like super dry Merck and using freshly opened bottles all at once. But then people piss and moan about the higher price.

There's a lesson in human nature for you.

I am working on a non-SO3, non-oleum and non-sulfur chlorides method for producing practical quantities of SOCl2 from SO2 and hexachloro-m-xylene using FeCl3 (anhydrous) as catalyst. In this country SOCl2 is banned so making it is only option and oleum is too bloody expensive. HCMX is not so hard to prepare. See the thread on this project. (SO2Cl2 -> SOCl2 Some Musings).

There is also reason to expect that SO2 will react with benzotrichloride and catalyst albeit more slowly. Benzotrichloride is commercially available. HCMX is too but horribly expensive.

Len1 tried this but used wrong catalyst, negative results.

Kyrides teaches that SOCl2 can be made from phthaloyl chloride and SO2 at 200 C over ZNCl2 in 66% yield.

So anyway we are closing in on more convenient preps of SOCl2 that can be done in glassware and that will be good news.

[Edited on 26-8-2008 by Sauron]

Formatik - 26-8-2008 at 20:08

@ Sauron: what you're saying seems in good accord with the patent procedure. I should have expounded on the process with a few more details so below is the translation of the patent process. In the second example they use AcCl, in the other trial part with SOCl2 they just substituted the AcCl below with 119 parts technical grade SOCl2, and using 180 parts AcOH also instead of the amounts below, to get Ac2O:

In a fractionating column and reflux condenser which is attached to it, which coolant is held at -15 to -20º, 200 parts glacial acetic acid are kept at boiling, so that the column is filled with acetic acid vapors. Then 131 parts of acetyl chloride are gradually added through a pipe which leads into the boiling acetic acid, and further heated until the hydrogen chloride evolution ceases showing the end of the reaction. Then the liquid left in the boiling vessel is subjected to a careful fractionated distillation yielding pure acetic anhydride. Yield: 90% of the theory.
Quote:
Originally posted by Klute
Congratulations! excellent work!


Yeah, second that. I also like seeing reactions get put to the test.

Sauron - 26-8-2008 at 23:25

AcOH and SOCl2 will give AcCl; AcCl will react with AcOH to form Ac2O. Nolo contendere.

The part I was barfing on, for lack of lit. support, was NaOAc + SOCl2 -> Ac2O. However, I am not prepared to say this does not work. I just doubt that it does. I don't think SOCl2 works same as oxalyl chloride, mechanistically, that is, through a double anhydride stage. So no reason to assume parallel reactions.

I'd like to see someone try it though. I can't - no SOCl2 and in Thailand it's verboten. So it would have to await my SOCl2 synthesis.

Formatik - 27-8-2008 at 00:02

Quote:
Originally posted by Sauron The part I was barfing on, for lack of lit. support, was NaOAc + SOCl2 -> Ac2O. However, I am not prepared to say this does not work. I just doubt that it does. I don't think SOCl2 works same as oxalyl chloride, mechanistically, that is, through a double anhydride stage. So no reason to assume parallel reactions


Can't say about SOCl2, but Beilstein cites a reference for the technical preparation of acetic anhydride using anhydrous NaOAc and sulfuryl chloride: G. Cohn in F. Ullmann, Enzyklopädie der technischen Chemie, 2. Aufl. Bd. IV [Berlin-Wien 1929], pg. 690, and maybe also something in: Gassner G.m.b.H., Häusler, McLang, Chem. Trade J. 76 [1925], 787. Beilstein also mentions pyrogenic dehydration of AcOH from DE 486953 (just the jist as given by Beilstein): the mixture of acetic anhydride vapor and water vapor is bound by addition of compounds, which builds azeotropic mixture with the water, then following condensation of anhydrous Ac2O.

Sauron - 27-8-2008 at 00:36

Yes but as you say. That's SO2Cl2. Despite the similarity in formula, these two compounds have vastly different chemistries. And they are not so easy to interconvert. SO2Cl2 mostly reacts as a stabilized form or source of SO2 and Cl2. Hence its employement with radical initiators as a free radical chlorinating agent. Sulfuryl chloride in ordinary temperatures is not a dehydrating agent. It can be mixed with cold water. (See entry in Merck.)

Formally SO2Cl2 is the acid chloride of H2SO3 and SO2 is the anhydride of that acid (sulfurous acid.) This is a convenient way of looking at it, but sidesteps the inconvenient detail that H2SO4 only exists in rather dilute aqueous solutions. So one could prepare SO2Cl2 rather expensively from SO2 and oxalyl chloride. Just mix and let the CO and CO2 evolve, reflux everything else. But why bother when just mixing SO2 and Cl2 over activated carbon or camphor is just as effective and a lot cheaper?

Anyway I think it's a mistake to draw any inferences from those citations re SO2Cl2, especially since they long ago vanished as industrial methods. I would not assume that they were understood mechanistically at the time.

Simple enough to try NaOAc and SOCl2 if one has them at hand.

We do know NaOAc and oxalyl chloride works, because Roger Adams recommended it in 1918 in JACS.

[Edited on 27-8-2008 by Sauron]

Attachment: RAdams.pdf (1.1MB)
This file has been downloaded 827 times

Jor - 22-9-2008 at 13:12

Sauron, you say sulfuryl chloride, SO2Cl2 , is the acid chloride of sulfurous acid. I'm almost sure it's not, it's the acid chloride of sulfuric acid (S is in 6+ oxidation state, each OH-group in H2SO4 replaced by Cl). Hydrolysis of sulfuryl chloride will result in sulfuric acid and HCl. I'm not sure, but I think action of SO2Cl2 on methanol yields dimethylsulfate. It will at least form methyl chlorosulphate/methylsulfuric acid

SOCl2 is the acid chloride of sulfurous acid.

Can't acetic anhydride be prepared by means of action of CO upon methyl acetate, or does this reaction require veryy high temperature/pressure, or expensive catalysts?

[Edited on 22-9-2008 by Jor]

Sauron - 23-9-2008 at 00:59

H2SO3 only exists in dilute solution and cannot be isolatred.

Chlorinating SO2 produces sulfuryl chloride if elemental chlorine is reacted with SO2 over AC or camphor.

So thanks but the correction is rather useless.

Chlorinating SO2 with phthalyl chloride does produce thionyl chloride.

Formatik - 24-9-2008 at 19:51

Quote:
Originally posted by S.C. Wack
Quote:
Originally posted by hector2000
this method is not true
no anhydrid will be make


Ber. 9, 444 (1876): "Nach Versuchen der HH.H. Gal und A. Etard kann Essigsäure unter günstigen Umständen durch Phosphorsäureanhydrid in Essigsäureanhydrid umgewandelt werden. Man trägt ziemlich rasch 30 Grm. Phosphorsäureanhydrid in 60 Grm. Essigsäure ein, indem man durch beständiges Schütteln dafür Sorge trägt, dass die beiden Substanzen sich möglichst schnell vermischen. Das Gemenge wird bald braun und erhitzt sich etwas, in diesem Momente destillirt man rasch ab und isolirt das gebildete Essigsäureanhydrid durch die fractionirte Destillation. Die Verfasser haben auf diese Weise ungefähr 3 Grm. der letzteren Verbindung erhalten. Benzoësaure auf ähnliche Weise mit Phosphorsäureanhydrid behandelt liefert eine geringe Menge Benzoësaureanhydrid."

OK so the yield is a little low if true. This is not the same as "no". IIRC Étard killed himself, but not over cries of bullshit on this.



P2O5 could be used decently indirectly, to the preparation of Ac2O, by using either of the following: 1. Ber., 10, 1790 mentions passing dry HCl for 2 hrs into a mixture of P2O5 and GAA held at 0ºC during that time. The P2O5 absorbs the H2O which normally destroys the AcCl. The liquid is then distilled, AcCl is said to form in significant amounts. 2. Using P2O5 which can be heated with NaCl to form POCl3 (mentioned briefly here), which can be used to get the AcCl: 2 CH3COONa + POCl3 -> 2 CH3COCl + NaPO3 + NaCl. Then use the AcCl to get the Ac2O.

Sauron - 25-9-2008 at 00:49

"Mentioned briefly here"? The reaction of P2O5 and NaCl as described by Tarbutton in JACS, has been flly described here and the original paper posted by me. You make it sound like a trivial operation. In fact that reaction does not initiate below 400 C, requires a high pressure apparatus (autoclave) to handle the autogenous pressure and takes about 20 hours on even a modest scale. There are a lot easier ways to make acetyl chloride than to prepare POCl3 to make it - which is not a very good method anyway.

Few of us happen to have a large pressure reactor sitting around. Most people prefer to work in glass. There are at least half a dozen good methods for preparing AcCl that run fine in pyrex, and have been described on this forum.

As to the proposition of GAA and P2O5 being treated with anhydrous HCl, that is fine if you happen to have a large cylinder of dry HCl handy. I have been pricing control valves and regulators for exactly such a cyclinder and find that they cost about 6 times the price of brass regulators for noncorrosive gases. That is, about $600 US for the cheapest single stage stainless steel regulator I have found. So do you really think this is a practical approach after all? That is, assuming that the method works at all?

You can prepare acetyl chloride from:

GAA and TCT (cyanuric chloride) in acetone in presence of TEA

GAA and benzoyl chloride (1.5 to 2 excess of reagent) per H.C.Brown in JACS

GAA and phthaloyl chloride per L.F.Kyrides in JACS

GAA or anhydrous sodium acetate and oxalyl chloride per Roger Adams in JACS

or from GAA and Ph3P in CCl4

Or you can go straight to Ac2) from anhydrous sodium acetate, bromine and sulfur; or from oxalyl chloride and anhydrous sodium acetate in different proportions than for preparing AcCl.

Most assuredly if I were to go to the trouble of making POCl3 I would not waste it on preparation of acetyl chloride for which so many other less precious reagents and simpler methods are at hand.

The same is true of thionyl chloride.

There arer several more mild neutral preps of acetyl chloride and other acyl chlorides, likewise described here previously.



[Edited on 25-9-2008 by Sauron]

zed - 12-10-2008 at 13:38

Ummm. Well, there is the possibility that you can produce acetic anhydride, simply by mixing glacial acetic acid, with isopropenyl acetate, and distilling off acetone.

I haven't heard that isopropenyl acetate is restricted.

Am I missing something?

Sauron - 12-10-2008 at 21:14

What is the basis for your assertion that Ac2O can be had by distilling GAA with isopropyl acetate?

Put some literature forward, please. Because I see nothing at all to this idea. I think it is nonsense.

zed - 12-10-2008 at 23:19

Isopropenyl Acetate. AKA Methyl Vinyl Acetate. The enol ester of acetone. You know, the one that is created by reacting acetone with ketene. U.S. $54.20 a liter via Aldrich. Product Number 117781

Interesting stuff.

It is used as an acetylating agent. It can acetylate cellulose, and In fact, it may be used to manufacture anhydrides.

So, you're kidding me right? You always did have such a wonderful sense of humor.

It really never occurred to you, that you might be able to produce acetic anhydride by mixing Isopropenyl Acetate with Glacial Acetic Acid? And then, drive the reaction to completion by removing acetone as it forms?

Think about it.

http://www.britannica.com/EBchecked/topic/25412/anhydride
http://www.informaworld.com/smpp/content~db=all~content=a757...
http://www.freshpatents.com/Method-for-the-production-of-ace...
[Edited on 12-10-2008 by zed]

[Edited on 12-10-2008 by zed]

[Edited on 12-10-2008 by zed]

[Edited on 13-10-2008 by zed]

Nicodem - 13-10-2008 at 00:20

Isopropenyl acetate does indeed acetylate acetic acid to form acetic anhydride, but as far as I remember you need a catalytic amount of TsOH or other acids to reach equilibrium fast enough. Just refluxing acetic acid with isopropenyl acetate without acid catalyst and removing acetone trough fractionation might take too long. Anyway, Sauron and Hector already made a looong discussion on the subject. There were patents posted about this reaction using the cheaper vinyl acetate instead. Isopropenyl acetate is twice the price of acetic anhydride.

zed - 13-10-2008 at 01:12

Price is not the problem. A lot of the guys would like to have a little acetic anhydride.

Making it from Isopropenyl Acetate might be cheap enough, and probably relatively safe.

Here in the U.S., I think I could obtain A.A. fairly easily. In other parts of the world, closer to the poppy fields, it might be very tough to acquire.

As for fractionating, I do not know if it would be required. Acetone has a much lower boiling point than Isopropenyl Acetate, Acetic Anhydride, and even Glacial Acetic Acid.

And, since we are talking about an equilibrium.....It is conceivable that the acetone might be removed from the reaction mixture below normal reflux temperature, via vacuum distillation. Thereby reducing the formation of byproducts.

Having read the Hector thread, and the 18 pages of this thread, I did not recall any mention of Isopropenyl Acetate. So, I figured maybe it had been overlooked.



[Edited on 13-10-2008 by zed]

Sauron - 13-10-2008 at 01:52

Isopropenyl acetate = methyl vinyl acetate, all right. If you go back far enough in the thread you will see that I posted several papers dealing with vinyl acetate in similar reactions, also involving catalysts. Somewhere around here I have a large bottle of stabilized vinyl acetate monomer, which I purchased for the purpose of trying this out. However I have not yet done so as for various reasons my hood is not yet installed.

I assume methyl vinyl acetate also is a monomer requiring stabilization and therefore needs distilling prior to use in this reaction? '

I await someone actually performing this reaction and reporting success and preperative details.

Till then it seems to me there are quite a few better reactions out there than this one. Put not your faith in patents, sayeth Sauron. They'll bugger you every time.

[Edited on 13-10-2008 by Sauron]

Formatik - 13-10-2008 at 02:15

Quote:
Originally posted by Sauron
"Mentioned briefly here"? The reaction of P2O5 and NaCl as described by Tarbutton in JACS, has been flly described here and the original paper posted by me. You make it sound like a trivial operation. In fact that reaction does not initiate below 400 C, requires a high pressure apparatus (autoclave) to handle the autogenous pressure and takes about 20 hours on even a modest scale. There are a lot easier ways to make acetyl chloride than to prepare POCl3 to make it - which is not a very good method anyway.


I cited it as a reference where it was only briefly mentioned there. Always good to know further details.
Quote:
As to the proposition of GAA and P2O5 being treated with anhydrous HCl, that is fine if you happen to have a large cylinder of dry HCl handy. I have been pricing control valves and regulators for exactly such a cyclinder and find that they cost about 6 times the price of brass regulators for noncorrosive gases. That is, about $600 US for the cheapest single stage stainless steel regulator I have found.


Anhydrous HCl can be simply generated from:

a. conc. HCl and H2SO4. I had a glass appartus scheme for this, but I'd have to search for it.

b. mixing NaCl and H2SO4 which foams up a bit (overflow potential) releasing HCl, this mixture can later be heated to increase rate of reaction: NaCl + H2SO4 = NaHSO4 + HCl.

And then likley by melting NaHSO4 and NaCl (both dry). I've used this mixture to generate HCl, but not from anhydrous salts.
Quote:
So do you really think this is a practical approach after all? That is, assuming that the method works at all?


I don't think Berichte publishes shady papers. The paper cites Friedel in a Compt. rend. paper who carried the reaction out at 80º, the Berichte paper brought the reaction down to a lower temperature.
Quote:
Originally posted by Jor Can't acetic anhydride be prepared by means of action of CO upon methyl acetate, or does this reaction require veryy high temperature/pressure, or expensive catalysts?


Carbonylation of methyl acetate is a known method of Ac2O production. US4544511 describes synthesis using MeOAc and Me2O but they do use catalysts and autoclaves.
Quote:
Originally posted by zed
Isopropenyl Acetate. AKA Methyl Vinyl Acetate. The enol ester of acetone. You know, the one that is created by reacting acetone with ketene.


If you intend on using ketene to get isopropenyl acetate, then why not just use ketene directly with GAA to get acetic anhydride?

[Edited on 13-10-2008 by Formatik]

Sauron - 13-10-2008 at 02:31

A pile of preposterous, impractical and unsafe blather.

Obviously you have a perculiar idea of what "anhydrous" means. If you generate HCl by wet methods you will need to scrub the gas to remove acid mist and some residual moisture. TANSTAAFL, after all. That what I mean by a handy cylinder.

We wasted many pages already arguing about ketene generation at home, it's an asinine idea, so don't do it. Furthermore since GAA can be used as a feedstock for ketent I suggest that the cited patent process will also produce some ketene, so same injunction applies. Of course if you are just a paper chemist and don't actually DO anything, then feel free to cite all the unworkable crap you care to and propose all the $100 million dollar industrial processes you want to. But not one drop of Ac2O will come of it.

Formatik - 13-10-2008 at 05:56

Here is the schematic for HCl being referred to. It's described in Lehrbuch der anorganischen Chemie by Hugo Erdmann pgs. 299-300. Heating fuming HCl acid, and then drying with pumice drenched with conc. H2SO4. A more complex set-up is described up until page 301 using a Kipp’s apparatus. Simpler would be to use the other suggestions.

HCl.jpg - 14kB

Sauron - 13-10-2008 at 07:19

YAWN. Wake up and smell the coffee, this is the 21st century not the 19th. Perhaps you want to go back to using alchemical symbols as well?

What is HCl and P2O5 supposed to fetch you? POCl3? In what time frame? Do you think a mixture of POCl3 and P2O5 just sits there and happily coexists? Sorry. They react with each other. As far as GAA is concerned you might get a little acetyl chloride, but then what? It'll be a bitch to seperate it from all that POCl3/P2O5 mess.

In short this is not a useful and practicable method, I don't see any Ac2O coming out of it, there are better ways to prepare POCl3 and there are lots of better ways to prepare Ac2O. If you'd spend a little time reading the pertinent threads you'd know that.

"Fuming hydrochloric acid"? All hydrochloric acid (conc) fumes. The term is meaningless. Fuming sulfuric acid is any sort of oleum of which common concentrations of dissolved SO3 run 20 to 65 per cents. Fuming nitric acid is any sort of nitric acid above d.1.42 up to a bit over 1.50. Fuming hydrochloric? It's redundant.

Formatik - 13-10-2008 at 15:05

Quote:
Originally posted by Sauron What is HCl and P2O5 supposed to fetch you? POCl3? In what time frame? Do you think a mixture of POCl3 and P2O5 just sits there and happily coexists? Sorry. They react with each other. As far as GAA is concerned you might get a little acetyl chloride, but then what? It'll be a bitch to seperate it from all that POCl3/P2O5 mess.


Beilstein was saying something about dehydration, the Berichte paper describes the excess P2O5 acts on CO.OHHCl groups and converts it to the chloride, but they also hold it possible to work dehydrating.
Quote:
In short this is not a useful and practicable method, I don't see any Ac2O coming out of it, there are better ways to prepare POCl3 and there are lots of better ways to prepare Ac2O. If you'd spend a little time reading the pertinent threads you'd know that.


Very well.
Quote:
"Fuming hydrochloric acid"? All hydrochloric acid (conc) fumes. The term is meaningless. Fuming sulfuric acid is any sort of oleum of which common concentrations of dissolved SO3 run 20 to 65 per cents. Fuming nitric acid is any sort of nitric acid above d.1.42 up to a bit over 1.50. Fuming hydrochloric? It's redundant.


Well then we know not below concentrated is best suited.

[Edited on 13-10-2008 by Formatik]

zed - 13-10-2008 at 18:04

Formatic,

"If you intend on using ketene to get isopropenyl acetate, then why not just use ketene directly with GAA to get acetic anhydride?"

I never suggested using ketene. My suggestion was to buy some Isopropenyl Acetate, and then use it to prepare a modest amount of acetic anhydride. Isopropenyl Acetate is fairly safe to handle.

As for anhydrous HCl, It is readily generated by the action of Concentrated H2SO4....on rock salt. Cheap and easy. The expense is inconsequential. I would never consider buying HCl by the cylinder. Very expensive to work with, and here in the States, it might be considered a suspicious acquisition.

Sauron,

You have some vinyl acetate? Hmmm. Might it be oxidized to acetic anhydride via the Wacker? Or, has this option already been discussed?

Sauron - 13-10-2008 at 20:41

Ketene in a home lab = DEATH. If you bother to study the cumulative knowledge base on Ac2O you will see that it is not necessary to kill yourself to make Ac2O.

Ketene is good in an industrial setting, not in a home lab. FORGET ketene or proceed at your own peril.

You have literature on a Wacker oxidation of VA -> Ac2O?

If not I suggest focusing on the dozsen or so good practicable methods that are suitable for a home lab.

NOT industrial processes. Ac2O is highly flammable unlike GAA and at 800 C is a serious problem from so many standpoints: corrosiveness, flammability, toxicity. You wanbt to deal with superheated Ac2O vapor in your home? Not me.

zed - 14-10-2008 at 00:47

Ah, a misunderstanding. I'm not talking about the Wacker process for producing Acetic Anhydride Via Ketene.

I'm suggesting that Acetic Anhydride might be produced by the Wacker oxidation of terminal alkenes. Like Vinyl Acetate. This would be analogous to the Wacker oxidation that is performed on terminal alkenes, to produce Methyl Ketones. A reaction that proceeds under mild conditions.

Since Vinyl Acetate is often made by the reduction/dehydration of Acetic Anhydride, it is reasonable to conjecture that Vinyl Acetate might be reoxidized, back into Acetic Anhydride.

No home lab here. I either build a real lab, or facsimile thereof, or I visit the Uni.

It is important for a gentleman, to avoid the appearance of possible impropriety.

Moreover, as an organic chemist, it is important to avoid working without a modern fume hood.

Sauron - 14-10-2008 at 03:27

Well, I certainly concurr with your last remark.

quarterfinal - 14-10-2008 at 11:30

i know i am a bit late.
i read all the posts and just wanted to ask.
if i have some 500grams of red phophorus. a chlorine source and sodium acetate.
what should be my easiest route to acetic anhydride

Sauron - 14-10-2008 at 11:39

Save your red P for something else.

Is your sodium acetate anhydrous or is it the trihydrate?

If the latter you need to dry it. Honestly you are better off buying commercial anhydrous sodium acetate than messing with the trihydrate. The commercial anhydrous NaOAc needs minimal drying, or no drying. Do not open bottle till you are ready to use.

Now go back upthread and see my summary of your reaction options.

Next, do you have a fume hood?

You can prepare acetyl chloride from:

GAA and TCT (cyanuric chloride) in acetone in presence of TEA

GAA and benzoyl chloride (1.5 to 2 excess of reagent) per H.C.Brown in JACS

GAA and phthaloyl chloride per L.F.Kyrides in JACS

GAA or anhydrous sodium acetate and oxalyl chloride per Roger Adams in JACS

or from GAA and Ph3P in CCl4

Or you can go straight to Ac2) from anhydrous sodium acetate, bromine and sulfur; or from oxalyl chloride and anhydrous sodium acetate in different proportions than for preparing AcCl.

Most assuredly if I were to go to the trouble of making POCl3 I would not waste it on preparation of acetyl chloride for which so many other less precious reagents and simpler methods are at hand.

The same is true of thionyl chloride.

There arer several more mild neutral preps of acetyl chloride and other acyl chlorides, likewise described here previously.


With acetyl chloride and ANHYDROUS NaOAc you have the makings of Ac2O at hand.

[Edited on 15-10-2008 by Sauron]

quarterfinal - 14-10-2008 at 11:48

well yes first i have a fune hood, bought it from a friend who was moving. the sod acetate is anhydrous and unopened.

quarterfinal - 14-10-2008 at 11:52

yeah but i couldnt get my hands on any tct etc. i thought maybe since i had the phos i could use it . since i dont have any better use for it anyways
i might be able to get a bit of sulphur too

Sauron - 14-10-2008 at 11:56

In that case you have an ambarassment of choices of ways to make AcCl from GAA and then react AcCl with freshly fused anhydrous NaOAc.

Also a few ways to get directly to Ac2O from GAA or anhydrous NaOAc.

One of those is sulfur, bromine and anhydrous NaOAc. Details have been posted on here before. You get a pasty yellow muck but distilling gets you Ac2O out of that. It's an old Russian prep.

quarterfinal - 14-10-2008 at 12:03

could you come again on that one a little detailed
what are the expected yields etc

Sauron - 14-10-2008 at 12:06

If you insist on using your red P then with 500 g of that you can produce a few Kg of PCl5

With PCl5 you can produce oxalyl chloride from ANHYDROUS oxalic acid.

And with oxalyl chloride and anhydrous NaOAc (freshly fused) in the right proportions you can produce Ac2O.

Note that PCl5 and oxalyl chloride are no fun to handle. Gloves, goggles, hood.

[Edited on 15-10-2008 by Sauron]

quarterfinal - 14-10-2008 at 12:08

what about the Hell-Volhard-Zelinsky reaction , does it help and work here

Sauron - 14-10-2008 at 12:11

The HVZ reaction is for making alpha-haloacids not acid chlorides. Chloroacetic acid is of no use to you in making acetic anhydride. None at all.

Acetyl chloride is CH3C(=O)Cl

Chloroacetic acid is CH2ClC(=O)OH

The reaction you are after is CH3C(=O)Cl + NaOC(=O)CH3 -> (Ch3C(=O))2O + NaCl

[Edited on 15-10-2008 by Sauron]

quarterfinal - 14-10-2008 at 12:27

i just checked with a friend he has about 400grams sulphur powder. how do i go about from that

Sauron - 14-10-2008 at 12:36

You still need bromine.

The Russian prep of acetic anhydride takes Br2, freshly fused (melted then ground) NaOAc and sulfur,

quarterfinal - 14-10-2008 at 12:43

although i i think i can get oxalic acid, and proceed with the phos method. still what do you think about this method it does not require br.
synthesis, generating sulfur chloride in situ:Mix quickly and thoroughly 205-215 g of pulverized fine NaOAc and 10g dry sulfur powder, the mixture is quickly transferred to a wide-mouth 1 liter RBF and wetted w/25 ml acetic anhydride. Into the flask through the rubber cork extend 1) a wide tube for chlorine in-flow 2) an overhead stirrer, which is sealed with the aid of a piece of rubber tubing greased with vaseline and 3) an out-leading tube for excess Cl2 release. The flask is immersed in an ice-bath. Chlorine is initially passed in very carefully, with frequent stirring or shaking, over the passage of time the rxn gets hotter and more and more liquid, so the stirrer may bee after some time rotated with a motor. Chlorine stream should bee regulated so that almost all of it is absorbed. When the reaction mixture stops heating and Cl2 is no longer taken up, the rxn contents are distilled in vacuo at oil bath temp ~150-180°C, then redistilled at ordinary pressure, collecting the fraction boiling between 132 and 142°C. Yield ~90%.

Sauron - 14-10-2008 at 12:50

I think you would be better off preforming your sulfur chloride and I think you would be well advised knowing whether you need SCl2 or S2Cl2, and how to seperate these and convert one to the other. The in-situ proposition allows no such control.

S and Br2 do not share this problem as they can only combine one way.

quarterfinal - 14-10-2008 at 12:53

ok this i think is for s2cl2
Prepare 100g freshly fused NaOAc and 65g S2Cl2. A small quantity of NaOAc is placed in a thin-walled glass cooled in an ice bath. To this is added some sulfur chloride, the mixtr is vigorously stirred w/a wooden spatula, not allowing the temp to rise. Then some NaOAc is added again, and the process is repeated several times until all is mixed in. The semi-liquid mass is transferred into a 1 liter RBF. The previous operation is repeated 4 times, so that 400g NaOAc and 260 g S2Cl2 total are taken into work. The RBF is then equipped w/a reflux condenser and gently heated on a water bath to ~80-85°C. As soon as the rxn starts, the heating is removed, and in case the rxn gets too vigorous it's cooled w/cold water. After 20-30 min SO2 evolution ceases and the mixture is heated for 10 more min's on a boiling water bath. The rxn product is then distilled off under vacuum, then fractionally re-distilled at ordinary pressure, collecting the fraction boiling between 132-142°C.

Sauron - 14-10-2008 at 13:06

Yeah, people here read Rhodium too, you know?

I would advise you to do it all in a RBF and use mechanical stirring because the proposed transfer would be a nightmare.

And first you need to prepare S2Cl2 and purify it. See Brauer for details. It's no fun, you would be happier with Br2.

quarterfinal - 14-10-2008 at 13:17

ch3cooh+socl2=====ch3cocl +so2 +Hcl
The separation is simplified to an extent because the by-products are both gases. You would obviously still have to fractionally distil the mixture to separate the acyl chloride from any excess acid or sulphur dichloride oxide.
now the question is how do i make socl2

Sauron - 14-10-2008 at 17:56

Not one that I recommend. Did you come here for help, or to have some place to post these tired old hackneyed and half baked writeups from druggie sites? Like the page you drew all of these from?

http://www.erowid.org/archive/rhodium/chemistry/anhydrides.h...

Because this site is about chemistry not cookery.

Where do you intend to get SOCl2? It's not on anyone's "A" list for chlorinating reagents for the lower three acyl halides. See Vogel's remarks about this. SOCl2 is always used in excess, and the excess SOCl2 is too proximate to AcCl to easily fractionate. The same problem holds for PCl3 and POCl3, not that you can make PCl3 from your red P anyway, because you can't. Chlorination of red P gets you PCl5 only.

The government watches it closely in US because of its notorious use in production of certain chemical weapons. Making it is NOT easy, simple, or cheap.

Honestly, you sound like a ringer. Got 500 g red P huh? And a fume hood? But you can't get basic common and even OTC reagents.

Well, sunshine, go find another sandbox to play in. This one is foir the big kids.

I'm through with you.


[Edited on 15-10-2008 by Sauron]

[Edited on 15-10-2008 by Sauron]

Formatik - 15-10-2008 at 02:06

Quote:
Originally posted by Sauron "Fuming hydrochloric acid"? All hydrochloric acid (conc) fumes. The term is meaningless. Fuming sulfuric acid is any sort of oleum of which common concentrations of dissolved SO3 run 20 to 65 per cents. Fuming nitric acid is any sort of nitric acid above d.1.42 up to a bit over 1.50. Fuming hydrochloric? It's redundant.


Belated correction here. But in German "concentrated HCl" is 24-36% HCl (d = 1.12-1.18). "Fuming HCl" is 37-40% HCl (d=1.18-1.20). Both will work, but the latter is to the higher region of the concentration spectrum.

[Edited on 15-10-2008 by Formatik]

Sauron - 15-10-2008 at 02:44

Well, everywhere else, concentrated HCl is the solution of HCl and H20 as described in Merck Index, among other places, and the ACS documentation on their reagent grade chemicals. You will find that the concentrated acid is also defined by molar concentration. About 11.75M

Merck Index 12th Ed: Fumes in air. May be colored yellow by traces of iron, chlorine, and organic matter. Reagent grade concd hydro chloric acid contains close to 38.0% HCl. 83 ml of concd HCl poured into sufficient water to make 1 liter yields approx 1.0 N HCl. The pH of 1.0 N HCl is 0.10; of 0.1 N = 1.10; of 0.01 N = 2.02; of 0.001 N = 3.02; of 0.0001 N = 4.01. n D 18 (1.0 N soln) 1.34168 . d 4 15 1.05 (10.17% w/w soln); 1.10 (20%); 1.15 (29.57%); 1.20 (39.11%) . Freezing pt: minus17.14degrees (10.81% soln); minus62.25degrees (20.69%); minus46.2degrees (31.24%); minus25.4degrees (39.17%), Gmelin prime s, Chlorine (8th ed.) 6, 136-137 (1927). Constant boiling azeotrope with water bp 760 108.58degrees contg 20.22% HCl , d 4 15 1.096 . Boiling weaker or stronger aq solns results in loss of either component until the constant boiling acid is obtained. Density: d 4 15 1.05 (10.17% w/w soln); 1.10 (20%); 1.15 (29.57%); 1.20 (39.11%); d 4 15 1.096.

So if we follow your purported German standard then all reagent grade HCl is "fuming" hydrochloric acid" which is ridiculous, as in almost 50 years in chemistry that is a term I have never seen or heard till now. By the way Merck is a German company, isn't it? Ot should I say, nicht wahr?

[Edited on 15-10-2008 by Sauron]

jarynth - 15-10-2008 at 03:53

Quote:
Originally posted by Formatik
in German "concentrated HCl" is 24-36% HCl (d = 1.12-1.18). "Fuming HCl" is 37-40% HCl (d=1.18-1.20).


I also ran into that distinction. Some sellers (even OTC) seem to take it very seriously and like to specify the formal 'fumingness' of their product.

Sauron - 15-10-2008 at 04:09

The constant boiling (azeotropic) HCl/H2O system is only 20-22% HCl, so what the German "spec" means is anything over the azeotrope can be called "concentrated" while anything meeting or exceeding the reagent grade in rest of the world (where it is called concentrated)) is termed "fuming". ???

This is absurd and illogical. All hydrochloric acid over the azeotrope fumes, so what? Constant boiling HBr and HI certainly fume, nobody calls them "fuming hydrobromic acid" etc. Obviously the standard is for the convenience of the manufacturers, not for the chemists and technicians who use the stuff. I am not at all a jingoist but in this case the ACS standard serves the industry and the academic community better. 24 to 36 % concentrated? Nope!

Nicodem - 15-10-2008 at 05:41

Beilstein has its own nomenclature and terminology for reagents, their properties and concentration. It is a German abstraction system from the end of the 19th century and as such it has its own peculiarities, but it is still the best there is. It is pointless and off topic to discuss about how logical it's terminology is in this thread. Please let's keep this thread short by posting only quality stuff and leave the details for U2U. Also, Sauron, please do not waste time with people who are too lazy to even use the shift key when writing down chemical formulas. It leads to nowhere and ends up in the usual manner.

Formatik - 15-10-2008 at 19:31

It's a subjective term just like some fuming acids. Concentrated nitric acid also gives off fumes, but the fuming strength of "fuming nitric acid" gives it its name. I've got a reference named Chemikalienkunde by H. Dietz, etc. that says fuming HCl fumes "very strongly". I've got 31.45% and it fumes, albeit not strongly. But I have noticed that its fumes are better visible in moist air, Germany is known by its humid weather.

quarterfinal - 28-10-2008 at 21:52

seems no one here has been able to carry out an easy synthesis as yet for anhydride. i read the previous posts and i tried the synthesis from vinyl acetate + h2so4 or hcl +acetic cid . and made a little aceticanhydride. but hte yield was pretty low.

Sauron - 28-10-2008 at 23:15

It's one of those mystery-catalyst things.

Regarding the pruported reaction of HCl gas and P2O5: It can't work. Here is why.

If you succeed in forming POCl3 from P2O5 and dry HCl, you split off H2O in the reaction.

The water can hydrolyze any POCl3 formed, but let's assume that you are lucky and the water reacts selectively with more P2O5 present instead. This will form H3PO4 so you now have in your pot: P2O5, POCl3 and H3PO4. H3PO4 and P2O5 together form polyphosphoric acid and if you think POCl3 will peacefully coexist with any of the above I suggest you read a little more fundamental Phosphorus chemistry because it won't.

Let's look at some stoichiometry:

6 HCl + P2O5 -> 2 POCl3 + 3 H2O

so we need excess P2O5 to remove the water

P2O5 + 3 H2O -> 2 H3PO4

So 1 mol excess P2O5 will do that. But now we have 2 mols H3PO4 in our pot along with 2 mols POCl3

I think it is naive to assume that the water formed from reaction of HCl gas and P2O5 will not destroy any or all POCl3 formed.

So this reaction is a muddle.

Can POCl3 be distilled off as it forms? Maybe but I doubt it.

[Edited on 29-10-2008 by Sauron]

Nicodem - 29-10-2008 at 00:03

In Gmelin you can find references for the preparation of POCl3 from P2O5 by using HCl, NaCl, CaCl2 and several other chlorides. HCl reacts slowly at room temperature and it takes several days to reach the equilibrium between polyphosphoric acid and POCl3. Alkali chlorides require reactive distillation of POCl3 out of the mixture as it forms and the reaction proceeds only at >200°C for most chlorides. If I remember correctly only VOCl3 is mentioned of forming POCl3 from P2O5 at room temperature in chloroform as solvent. It is several years since I checked Gmelin for these reactions so I might have remembered wrong about some details and besides I never went to read the original papers (I only have access to Gmelin at a library that is not close enough to just go and check again).
Interestingly, I could find nothing about the reaction of P2O5 with Lewis acid type chlorides such as FeCl3, ZnCl3 or AlCl3 which I would imagine should react at much lower temperatures than alkali chlorides (particularly FeCl3 given the favourable reaction thermodynamics). Apparently there was not enough interest in these reactions for the inorganic chemists to check.

Sauron - 29-10-2008 at 01:06

I've previously posted the reaction between NaCl and P2O5 which is done under autogenous pressure in an autoclave at 400-500 C. This was reported in JACS in 1940 by Tarbutton, I posted the paper which is mostly concerned with the analogous reaction with fluorides to form POF3 gas.

The byproducts are alkili phosphates.

A little PCl3 also forms, probably, according to Tarbutton, from Fe catalysis from vessel wall. This is up to 10% of the POCl3. HCl forms in proportion to any moisture in the NaCl.

It is an open question as to whether Tarbutton's hypothesis could be exploited to up the Fe catalysis and obtain a higher proportion of PCl3, or even exclusively PCl3, which would make me very happy as there is no good way to prepare PCl3, not even from red P or from PCl5. Oh, there are procedures but ask garage chemist who has tried them and he will support my generalization.

Whereas there are lots of ways to make POCl3.

The particular prep advanced upthread did not involve a closed system, just bubbling dry HCl into P2O5 (I assume with exclusion of atmosphere) and without any discussion of reaction time or stoichiometry. I am damned sure POCl3 will react with H3PO4, PPA or P2O5 to ptoduce some higher oxo acid or anhydride. PPA as you know is not a simple H3PO4/P2O5 system but a complex mixture. So I have serious doubts about the preparative usefulness of P2O5 (excess) + dry HCl.

In the rxn of P2O5 with NaCl (and other chlorides) the temperature required happens to coincide with the vapor phase of P2O5 and also the transitional phase in its structure. Tarbutton makes no mention, but of you look at the lit. on reaction of P2O5 with anisole under similar consitions this aspect is discussed in detail. (The product when P2S5 is used is Lawsson's Reagent.)

None of that is happening in this low temp reaction with HCl at atmospheric pressure.

[Edited on 30-10-2008 by Sauron]

Sauron - 29-10-2008 at 06:52

Further to the above, Tarbutton's reaction was conducted on the basis of the stoichiometry:

3 NaCl + P2O5 -> POCl3 + Na3PO4

in an iron or stainless steel bomb. The reaction with NaCl initiated at 250 C while that with CaCl2 required 400 C. The product mix was 75-90% POCl3, 10-25% PCl3 which the author speculated was from reduction of POCl3 by the vessel wall. The HCl in small amount was proportional to moisture in the reactants.

[Edited on 29-10-2008 by Sauron]

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Jor - 29-10-2008 at 15:19

That's sounds to good to be true. What is the reaction time?
If it's not too long, this may be as well a good route to acetic anhydride, hard to get for many of us (I'm blessed with a liter of the stuff).

In the acetic anhydride thread, I saw from anhydrous sodium acetate, acetyl chloride can be prepared via POCl3. Acetyl chloride then react with the exess sodium acetate to form acetic anhydride. This process was first not so preferred, due to the difficulty obtaining POCl3. But if it's this easily prepared and cheap (phosphorus pentoxide is quite cheap, at least it is at Acros/Baker, where I can buy). NaCl? Well i don;t have to tell.
I read in the PDF that only POCl3 is formed in a glass vessel exclusively.
So heating a mix of NaCl, anhydrous sodium acetate and phosphorus pentoxide will give acetic anhydride?

However it would be important that the phosphorus pentoxide is dry, or metaphosphoric acid and pyrophosphoric acids might form, wich severely attack glass at those temperatures. AFAIK P4O10 does not, but I'm not sure.

If anyone wants to try this, please post results. I currently do not have P4O10, and it will take at least a month before I get it. I will buy it by the 500g (approx 15 EUR) or by the Kg (Acros, 26 EUR). Damn cheap chemical...

However, opening the container will significantly reduce quality right? So it might be be better to go for 2x 250g , a total of 20 EUR.

[Edited on 29-10-2008 by Jor]

Sauron - 29-10-2008 at 19:33

In my opinion there are a dozen better ways to make Ac2O than using POCl3, it is precious stuff. I listed these upthread.

I'm not sure what the reaction time is. It sounds like, with NaCl, the volatile products start distilling off as reaction commences c. 250 C. In a 1 L autoclave with valve open to a delivery condenser, how long will a mol of POCl3 take to distill? You won't get much more than 3 mols NaCl and 1 mol P2O5 into the working capacity (650 ml) of that vessel. Maybe 1.5 mols, probably not 2.

If 10 to 25% of the POCl3 produced is reduced to PCl3 as Tarbutton says, then I would fractionate these apart, the PCl3 is even more precious. I'd love to be able to reduce it all to PCl3.

Oxidizing PCl3 to POCl3 is a known process, reagent is KClO3. But it's the reduction that is more interesting.

I DO NOT recommend trying to combine the reactions, if you insist on wasting POCl3 to make Ac2O then preform the POCl3 and then react with anhydrous NaOAc. The PCl3 if any will not hinder anything as PCl3 also reacts with NaOAc to make Ac2O. But there are better ways! Benzoyl chloride. Phthaloyl chloride. TCT. If you can buy from Acros, you can buy cyanuric chloride and it is cheap.

The P2O5 does need to be dry or you just make HCl. Open it in a dry box (glove box) or at least an atmos-bag. P2O5 is flocculent and a mess to transfer. I buy the 250 g bottles and use them in one go.

Here is first pahe of the 1954 JACS paper discussing the three crystalline modifications of P4O10, their structures, the transition temperatures and associated vapor pressures. The temperature ranges are the same as for Tarbutton's reaction and I say this is no coincidence. In this transition some P-O bonds are broken and clearly the forms at these temperatures are more reactive. See also the reference to another JACS paper by Hill and coworkers cited on this page.



[Edited on 30-10-2008 by Sauron]

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Jor - 30-10-2008 at 10:56

Yes Sauron I understand POCl3 is precious stuff, but I do not think it is if this method really works. P4O10 is cheap, and not so hard to get for most of us. (not regulated)
So if POCl3 will be be easy to make from available chemicals, it is not that 'precious' and it can be used to make Ac2O.

It's quite interestng for me, POCl3 is impossible or me to get, just as SOCl2, PCl5 and PCl3. That is because is list 3 CWC. I can however buy about any chemical at Acros/Fisher/Merck/Baker/Aldrich, but not CWC or some others. Red P, I can buy, so if I need it I can make PCl5 (I have about 250g red P).

Im not interested in the Ac2O, I have a liter here, wich I hardly use.

I know TCT is very useful and cheap. if I want I can buy it from Acros. But I dont' want it, as it is classified as 'very toxic by inhalation'. Is it that bad? Is it like NO2/Cl2 or like fosgene/AsH3/H2Se?
Fortunately I am almost finished building a hood.

I do not have a glove box. I want to make a dry box sometime. A box where I put the chem in, then dry it for about 2 hours with KOH or something like that, and then open container with inbuilt gloves. Future project.

Sauron - 30-10-2008 at 18:01

The glove/box/dry box is one issue, you can ger around it by using a cheap and disposable Atmos-bag assuming you have a cylinder of N2 or Argon.

You will also find that glass will not take contact with this reaction mix at these temperatures, so you will go through a few flasks but that is not a big deal. Really better to do this in stainless steel autoclave and if you haven't got one, it's a major expense.

The NaCl ought to be well dessicated. Baked out in a drying oven or heated in a crucible. I don't think it needs to be fused, just drive off any moisture.

Another very good way to make POCl3 is to buy red P, chlorinate it to PCl5, and use that to prepare oxalyl chloride from anhydrous oxalic acid. The byproduct is POCl3. But if you can't get red P this is a non-starter. It is actually a better way to make POCl3 than it is to make oxalyl chloride. That's because you need a lot of PCl5 (3 mols plus escess) to treat one mol oxalic acid (anhydrous) and even so yield is <50%. You get 3 mols ZPOCl3, though.

Here’s what Gmelin mentions

Formatik - 1-11-2008 at 09:00

Quote:
Originally posted by Nicodem
In Gmelin you can find references for the preparation of POCl3 from P2O5 by using HCl, NaCl, CaCl2 and several other chlorides. HCl reacts slowly at room temperature and it takes several days to reach the equilibrium between polyphosphoric acid and POCl3. Alkali chlorides require reactive distillation of POCl3 out of the mixture as it forms and the reaction proceeds only at >200°C for most chlorides. If I remember correctly only VOCl3 is mentioned of forming POCl3 from P2O5 at room temperature in chloroform as solvent. It is several years since I checked Gmelin for these reactions so I might have remembered wrong about some details and besides I never went to read the original papers (I only have access to Gmelin at a library that is not close enough to just go and check again).
Interestingly, I could find nothing about the reaction of P2O5 with Lewis acid type chlorides such as FeCl3, ZnCl3 or AlCl3 which I would imagine should react at much lower temperatures than alkali chlorides (particularly FeCl3 given the favourable reaction thermodynamics). Apparently there was not enough interest in these reactions for the inorganic chemists to check.


The formation by NaCl and P2O5 was long ago described by Lautemann in Lieb. Ann. 113 [1860] 240, but also Kolbe and Lautemann in Liebigs Ann. Chem. 147 [1868] 355/66, 361. The preparation through P2O5 with CaCl2 and NaCl in a Fe- or steel vessel , through the reduction of POCl3 with the Fe of the vessel some PCl3 forms, the reaction starts at 250ºC with NaCl, and 400ºC with CaCl2, which is from the Tarbutton already mentioned in this thread (JACS. 63 [1941] 1782/9, 1785). Gaseous HCl is absorbed at first slowly from P2O5, then quickly absorbed to a maximum and then gets absorbed more slowly again, likely according to the equation: 2 P2O5 + 3 HCl = POCl3 + 3 HPO3 (J. chem. Soc. 53 [1888] 756). Another way from P2O5 is by heating it with CCl4 to 200 to 210ºC in the ratio of: P2O5 + 2 CCl4 = COCl2 + CO2 + 2 POCl3, or 2 P2O5 + 3 CCl4 = 4 POCl3 + 3 CO2 (Ber. 5 [1872] 30; Z. Chem. [2] 7 [1871] 615). Clearly aim for the latter reaction where phosgene shouldn’t be formed. Several other methods are covered, there is indeed no mention of Lewis acid chlorides directly in a synthesis.

Sources: Gmelin, Syst. No. 22, Na, p. 329; and Syst. No. 6, Cl, p. 130; Syst. No. 16, P, Tl. C, p. 458-462.

Sauron - 2-11-2008 at 03:16

Thanks. Tarbutton's paper was primarily about the reaction of P2O5 with fluoride salts and the preperation and characterization of PF3, POF3 and some mixed chlorofluorides. The NaCl and CaCl2 reactions were a passing comparison, as were some reactions with rock phosphates. He did cite some references, but nothing as old as the Gmelin entries, and unfortunately not much of it accesible to me.
It is nice to have confirmation.

The CCl4 reaction is interesting. NaCl is a lot easier to come by though in these parts. I can get that Berichte paper from BnF, and the JChemSoc paper from RSC.

Thanks again!

Because now we can put this turkey to rest.

The reaction between HCl gas and P2O5 at normal temp and 1 atm requires almost 600 hours. 25 days, 3.5 WEEKS. The bulk of the uptake occured in first 5 days but absorption was still proceeding when they ceased measurements at 25 days.

The authors did not measure anything at elevated conditions, because they were just trying to clarify an anomaly in drying HCl gas stream over P2O5.

Now, perhaps this can proceed at a less leisurely rate at 1900 psig (the limit of my autoclave) and 325 C but we do not know that, so I must ask you in all honesty, is that what you would regard as a preparatively useful reaction?

It always pays to read the actual papers because reviews like Gmelin often omit insignificant details, like whether a reaction is actually good for anything. Like in this case, answer is "No."

[Edited on 2-11-2008 by Sauron]

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Sauron - 2-11-2008 at 04:56

The CCl4 reaction with P2O5 at 200-210 C takes place over 48 hours, and proceeds at an 80% yield (phosgene basis) in the case of the first stoichiometry.

This is not so worthless if one has a source for CCl4.

I agree that the phosgene-free second stoichiometry is to be preferred.

Here is the page 30, it is just a couple of paragraphs describing a report by a Herr Gustavson. Incidentally I got this from BnF because Wiley is missing Issue 1 of Volume 5, Berichte, so I could not get a proper citation there.



[Edited on 2-11-2008 by Sauron]

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Formatik - 2-11-2008 at 09:07

Thanks for finding the papers, in the Ber. they are also saying that only traces of COCl2 form in the 2 mol P2O5 and 3 mol CCl4 reaction. The original seems be the paper by G.Gustavson in the Ztschr. Chem. citation. They are also saying POCl3 and excess P2O5 react to form a thick, transparent mass that is left over after the POCl3 was distilled off. Further I’ve found that this mass is metaphosphoryl chloride: which forms when P2O5 and oxychloride are heated in the right ratio to 200º during 36hrs: P2O5 + POCl3 = 3 PO2Cl (Gustavson, Ber. 4, [1871] 853) and speculates it might be mixed with a polymer. Huntly (J. chem. Soc. 59 [1891] 202-8) says the reaction is more complicated and forms additionally P2O3Cl4 and P7O15Cl5. The reason why Gmelin cuts short on details is because this information didn't appear under the main preparation entries, which stick out like sore thumbs. Here is the files, they are clearest at about 65 to 75% zoom.

[Edited on 2-11-2008 by Formatik]

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Sauron - 2-11-2008 at 10:28

Thanks, I do appreciate your kindness.

The full cirarion for the above paper:

Vorläufige Mittheilung über die Reaction des Phosphoroxychlorids auf Phosphorsäureanhydrid
G. Gustavson
Bar., 4, 853 (1871)
DOI: 10.1002/cber.187100402104

I will post it shortly.

Meanwhile here is the 1891 Huntly paper from J.Chem.Soc.




[Edited on 3-11-2008 by Sauron]

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Sauron - 2-11-2008 at 15:55

G.Gustavson:

Regarding his report of the reactions of CCl4 and P2O5 at 200-210 C for 48 hrs, I would be interested in the mechanism of this reaction. A thermally initiated free radical mechanism seems likely, one involving perhaps the initial formation of the ubiquitous (with CCl4) trichloromethyl radical and a chlorine radical. If this is a FR reaction then perhaps temperature or time can be reduced by UV photolysis, or peroxide initiation.

A further question is whether a similar reaction works with CHCl3.

P2O5 + 2 CHCl3 -> 2 POCl3 + H2O + 2CO perhaps?

The short note attached concerns his study of the reaction of P2O5 and POCl3 to give metaphosphoryl chloride at 200-120 C/36 hours.





[Edited on 3-11-2008 by Sauron]

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Sauron - 2-11-2008 at 22:25

Back to the uptake of dry HCl by P2O5:

I should not have been so dismissive of this. I think that run as a pressure reaction at elevated temperature this is probably very practical and certainly as cheap as NaCl or cheaper. Most members simply do not have any pressure equipment to speak of.

A Parr bottle will at best afford 6 bar and 90 C. That is pushing things a little.

What Ace sells as glass pressure reactors are 40-50 psi (3 bar)

A Parr autoclave, of SS and normal design 1900 psi and 325 C.

The above are listed in increasing order of cost and decreasing likelihood of being in a home lab.

I have the first and third. 500 ml Parr heated shaker and 1 L Parr stirred heated pressure reafctor.

I do not presently have bottled HCl gas. The required stainless steel regulator for a full sized cyclinder is pricey, but sooner or later I will have to get one. I already have ordered 5 SS diaphragm valves for lecture bottles so I can buy a few LBs from Aldrich, and have them filled locally. Enough HCl to see what conditions work most efficiently.

----------

A complication when trying an unknown reaction with H3PO3 is that it is a tautomeric compound. Usually it exists as "phosphonic acid" HP(=O)(OH)2in pentavalent state. But its triesters and trihalides are the tervalent form reflecting the parent structure of phosphorous acid P(OH)3.

Its anhydride P4O6 (aka P2O3, phosphorus (III) oxide or trioxide, or tetraphosphorus hexaoxide, reacts very differently with water than does P4O10. The latter merely hisses when thrown into water and forms H3PO4 like a well behaved anyhydride.

P4O6 added to hot water decomposes violently to phosphine, H3PO4 and red P. In cold water it is slightly less spectacular.

So my hypothesis about its reaction with oxalyl chloride are rather speculative. However as P4O6 is "unobtainium" I won't be finding out. I'll be reacting the oxalyl chloride with H3PO3 instead.

[Edited on 3-11-2008 by Sauron]

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Sauron - 3-11-2008 at 18:09

It is probably better to let this thread return to its OT focus (making Ac2O) rather than continuing this tangent about making POCl3, albeit for that purpose.

See Inorganic Phosphorus Transformations in the Chemistry in General forum

Ephoton - 14-11-2008 at 01:59

after reading nicodems post on preparing benzoyl chloride from tcca and benzaldehyde I can not see why sodium acetate acetaldehyde and tcca in
methylene chloride at 40 C for three hours will not work.

the patent he posted was FR2633616 (A1)

Sauron - 14-11-2008 at 02:54

Well, for starters I am skeptical of patents unless there is supporting peer reviewed literature available and accessible.

Secondly, assuming that aldehydes and TCCA give acyl chlorides, which is news to me, then I would recommend preforming the acetyl chloride and reacting it with anhydrous NaOAc in a second step.

Finally, this would best be done in a pressure vessel since acetaldehyde is low boiling and it is going to be hard to reflux it without losses through condenser for three hours over a 40 C pot, even if you use a Dewar condenser.

In the end if it does work just add it to the LONG list of well documented methods of making AcCl and Ac2O which have been elaborated in this thread and prior threads on same subject.

Nicodem - 14-11-2008 at 03:19

Quote:
Originally posted by Ephoton
after reading nicodems post on preparing benzoyl chloride from tcca and benzaldehyde I can not see why sodium acetate acetaldehyde and tcca in
methylene chloride at 40 C for three hours will not work.

the patent he posted was FR2633616 (A1)

Well, if you would actually read the patent instead of generalising the reaction, you would notice that only nonenolisable aldehydes can be oxidized to acyl chlorides this way.

Sauron, the radical chlorination and bromination of nonenolisable aldehydes with N-haloamides and other such reagents to give acyl chlorides and bromides is well documented in the literature and industrial patents. The aldehydic hydrogen is easily abstractable and thus aldehydes often react in reactions based on radical mechanism (aldehydes even react with oxygen; for example the oxidation of benzaldehyde to benzoic acid on air, etc.).

Just a few examples:

With Cl2: WO2003072534, US20030130537, EP1176133, EP849253
With SO2Cl2: Tetrahedron, 25 (1969), 4363-4369.
With t-BuOCl: J. Am. Chem. Soc., 73 (1951) 702-704.
With NBS: Tetrahedron Letters (1979) 3809-3810.

Sauron - 14-11-2008 at 03:57

Thanks, Nicodem,for the clarification.

Ephoton - 14-11-2008 at 15:12

thanx my french is not the best.

what got me is the table they have and the examples.

under test 1 they state acetaldehyde with a 68% conversion
to acid halide.

due to my french being so bad I misunderstood.

what do they mean by this test.


[Edited on 14-11-2008 by Ephoton]

quarterfinal - 16-11-2008 at 10:09

i have been trying out the vinyl acetate method mentioneed in earlier threads and have succeeded in getting acetic anhydride . but the yield and purity are pretty bad. the yield is about 10% and the purity is about 60% or max 70%. there is a lot of acetic acid mixed with the product and its pretty hard to seperate with even careful fractional distillation.

Nicodem - 17-11-2008 at 00:54

Quote:
Originally posted by Ephoton
thanx my french is not the best.

what got me is the table they have and the examples.

under test 1 they state acetaldehyde with a 68% conversion
to acid halide.

due to my french being so bad I misunderstood.

what do they mean by this test.

I apologize. The French patent indeed states a 40-68% yield for acetaldehyde to acetyl chloride. It's been a few years since I checked it and seems like I mixed it up with some other paper on RCHO -> RCOCl where they claimed the reaction is only efficient for nonenolizable aldehydes or else side products resulting from alpha chlorination prevail. I will check the papers I have on this when I'll have more time. Meanwhile I checked on SciFinder and there is only one oxidation of MeCHO to AcCl listed, namely this same patent, which is suspicious to say the least. Searching for enolizable aldehydes to the corresponding acyl chlorides only gives a 3 other examples of which two are on less easily enolisable alpha-chloroaldehydes (JP06056739 and Zhurnal Obshchei Khimii, 28 (1958) 3004-3008), and one uses the decomposition of dibenzoyl peroxide in CCl4 to promote only the radical process and chlorinate isobutyraldehyde (Journal of the American Chemical Society, 69 (1947) 2916-2917).
Perhaps the dichloroisocyanuric acid (pKa 3.75 in water) which forms during the reaction is not acidic enough to catalyse the enolysation of acetaldehyde, particularly in the highly nonpolar CCl4 where its solubility and acidity is lower. Most examples of RCHO->RCOCl reaction use Cl2 where the side product is HCl and thus enolisation and consequent alpha-chlorination is inevitable.

Sauron - 17-11-2008 at 01:15

So the bottom line is that the sole patent is dubious and the yield sucks.

Not a very promising route.

Ephoton - 17-11-2008 at 02:42

only one way to find out for sure save the searching ill test the thing.
that is if time permits.
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