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Author: Subject: Acetic anhydride preparation
tupence_hapeny
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What precisely is the problem with the concept?

If not the concept that a dehydrating agent will in fact dehydrate a carboxylic acid – giving an acid anhydride (which is basically all that ketene does in the propionic anhydride synthesis – giving propionic anyhydride and acetic acid), which would appear to be somewhat settled, is the problem with the preparation of the metaphosphoric acid?

I realize that the nasty nature of this compound, as discovered on this forum: here

here

etc.

May be the problem when dealing with it in its liquid form, however, P2O5 is supposed to be fairly easy to use when dealt with in an admixture with DMSO, so I suggest that the easiest way to deal with the metaphosphoric and pyrophosphoric acids would be to make them via dehydrating them with charcoal (as per the patent), which would basically prevent the problems dealt with in the references above, and provide a dry medium from which they could be extracted with DMSO, DMF or (dare I say it) NMP (or whatever will work). Alternatively, the glacial acetic acid could be passed through a filter containing the charcoal/metaphosphoric acid mixture – giving acetic anhydride and charcoal/pyrophosphate.

NB For the synthesis of polyphosphate, see the synthesis of HI from H3PO4 on Rhodium’s site, the acid mixture is heated to 400C (which would cause the formation of HPO3) and then reacts with iodide to produce HI and a white, waxy, polymeric substance. I suggest that this may in fact be P2O6 (2HPO3 + I2 = 2HI + P2O6) which is, after all, a waxy, white, polymeric substance.

http://www.erowid.org/archive/rhodium/chemistry/hydriodic.ar...

Also see how else this same HI can be made, oh look, P2O5:

http://www.erowid.org/archive/rhodium/chemistry/anhydrous.hi...

BTW, I haven’t yet seen anywhere where this particular approach has even been attempted.

I intend to grab some phosphoric acid today, although that means that I also have to get some fucking bicarb, vinegar, dry acid, etc. as well.

The reason I suggested the metaphophoric acid is basically because it appears to act as a de facto higher phosphorus compound, plus the fact that it is a very strong dehydrating agent.

I suggested this method, as the production of elemental phosphorus goes from phosphoric acid, to pyro-metaphosphoric acid, while absorbed on carbon - I have seen no industrial process where anybody tries to do so in the liquid form - cause there ain't much it won't eat. The added benefit of the method from wood shavings is that if something is going to be dehydrated and oxidised, it will be the wood.

Anyhow, if you've tried it and it didn't work - that is a different story, however, I see no report from anyone that they have even made it this way- let alone tried it.

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Sauron
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I'm not interested. It's your idea, you try it. That way if it works you get the credit. And if it doesn't the only time wasted is your own.

I do have uses for P2O5 but this is not one of them.

I know multiple ways to make Ac2O that work very well. If I want Ac2O I use one of them. Same goes for acetyl chloride.

Some of the guys and gals have trouble getting some of the reagents, like TCT and oxalyl chloride. Fortunately I do not have his problem.
tupence_hapeny
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Sauron,

I have only, by UTFSE and reading my way through this entire post, only found one person who made any serious reference to this approach:

S.C. Wack

 Quote: Sort of. A Turkish professor unaware of it was studying the heating of metaphosphate with various salts in the 50's. Halogens were produced in an earlier article by heating the alkali halide salts with metaphosphate; and in this article the good doctor uses the theoretical amounts on a small scale with the halates, nitrite, nitrate, acetate, carbonate, sulfite, oxalate, and chlorides of Al, Mn, Cd, and Ni. The dry acetate was heated with alkali metaphosphate to 280-370C. 2 CH3COONa + Na2P2O6 --> Na4P2O7 + (CH3CO)2O, or so the author thinks. The patent used lower heat and GAA mixed in. The author's name gives no inventor hits at espacenet. There is nothing in the article that I can see (not speaking cheese-eating surrender monkey is a slight handicap) which suggests that the vapors were condensed and analyzed, which is not surprising given the small scale. At the end of the article, she seems optimistic that this can be used as a preparative method for acetic anhydride and promises to publish an investigation of this. Later. She died in 1992. So someone is going to have to try this, and I don't have metaphosphate on hand. It should be mentioned that except for this and the Pb acetate article that I mentioned earlier, there isn't a whole lot out there on heating acetates and not getting acetone or methane. There are some German patents and some Russian articles on heating Cu, Fe, Ni, Co, Ag, and basic Al acetates alone and getting the anhydride, but AFAIK these all use vacuum. Attachment: bull_soc_chim_fr_1259_1956.djvu (426.23 KiB) This file has been downloaded 99 times

As far as I can see, it should be possible, using that patent, to dehydrate the phosphoric acid/carbohydrate mix at between 150-200C. Unfortunately, at these temps it may still eat some glass. However, as most households contain at least one temperature controlled, self-contained heating, acid impervious (at that temp) appliance (electric frypan with teflon), it should be possible to get down to under 10% moisture.

From that point, the moisture limitations should prevent serious interaction between the pyrophosphoric/metaphosphoric acid and glass/ceramic, so in such way can it be taken to 400C and metaphosphoric acid.

Once carbon/metaphosphoric acid are to hand, it should be theoretically possible to simply mix the dry carbon/metaphosphoric acid with the glacial acetic acid and let the metaphosphosphoric acid slowly absorb water and transform itself into pyrophosphoric acid. All that would be needed is a sealed glass bottle/container - to prevent atmospheric moisture being absorbed.

My question is, is it possible to separate acetic anhydride from glacial acetic acid by fractional crystallisation, or is glacial acetic acid soluble in the anhydride?

tup

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Sauron
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You want to do a pressure reaction in a home appliance with two highly corrosive compounds?

The procedure you describe calls for a nice autoclave made of some nice corrosion resistant metal like SS or better, Hastalloy. Ac2O boils at 140 C, and is highly flammable. Any accident with your home appliance will rapidly degenerate into a disaster.

If you can't afford proper equipment don't do this reaction.

Of course, AcOH boils at 117 and is nonflammable. I doubt you will get any Ac2O so at least the fire hazard might not happen. But you will still have a bomb of hot angry glacial acetic acid and hot phosphoric acid (still liquid) -- no thanks! VERY unsafe.

[Edited on 11-4-2007 by Sauron]
tupence_hapeny
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Not a pressure reaction, I want to dehydrate the phosphoric acid with rice husk. I intend to start with an excess of rice husk and as it boils down, at 130-150C I will add the rest of the phosphoric acid. Of course, this is not suitable for the pressure reaction, that would be daft, would it not?

I will then transfer the mix to a baking tray (pyrex) and heat it in the oven at 250 for a number of hours. (Still without the acetic acid or even the sodium acetate). That will come separately.

BTW Am I the only one who thinks that the dichloroacetyl chloride from trichloroethylene could be converted into its anhydride rather simply?

Anyhow, here are two links (although I cannot access the full articles), in one P4O10 is used to make the anhydride of difluoroacetic acid:

http://jb.oxfordjournals.org/cgi/reprint/73/4/749.pdf

And in the other it is used to dehydrate dichloroacetic acid to its anhydride:

http://www3.interscience.wiley.com/cgi-bin/abstract/35000249...

If someone could get these articles I would be eternally grateful.

Another interesting aspect of this idea is that P205/Al2O3 is used to convert aldehydes to acylals with acetic anhydride. The supported reagent is used without solvent and is easily separated from the product(s) by filtration.

[Edited on 11-4-2007 by tupence_hapeny]

Attachment: Tetrahedron Letters 48 (2007) 2881–2884, 'P2O5-Al2O3 Catalysed Aldehyde to Acylal'.pdf (129kB)

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Sauron
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Goget the DOIs for those articles and request them yourself in References. That's what it is for.
tupence_hapeny
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I cannot get in there

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einstein(not)
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Has anyone looked at this patent?
http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=GB299342&a...
not_important
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 Quote: Originally posted by einstein(not) Has anyone looked at this patent? http://v3.espacenet.com/textdoc?DB=EPODOC&IDX=GB299342&a...

That's what 2&cent;_&frac12;&cent; has been talking about.
Sauron
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@tup, email Polverone or another moderator and request PW for References.

Heavan's gate will swing wide.

Just remember to always provide DOI
chemrox
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Which Na(x)PO4 is it? NaH2PO4? which one do you get mixing NaOH and H3PO4? is there a way to manipulate the outcome of mixing these?

[Edited on 17-5-2007 by chemrox]
tupence_hapeny
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I have just found some rather interesting articles on the topic (JACS)...

Here they are in order (3 part series) - they utilize benzoyl peroxide as a catalyst and proceed to perform some EXTREMELY interesting work with poor old, much maligned, sulfuryl chloride (see the third article):

http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1939/61/i08/...

http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1939/61/i12/...

http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1940/62/i04/...

They also use this compound to make benzotrichloride, which can be used to prepare phosphorus halides (from various phosphoric acids & the pentoxide), thionyl chloride, phthaloyl chloride, etc.

Just goes to show, there really is nothing new under the sun...

tup

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Sauron
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Perhaps you are unaware that the coauthor of those papers is the famous H.C."Boron" Brown, father of organoboron chemistry?

Anyway free radican chlorination with SO2Cl2 and an initiator is very well known and has been discussed on this forum previously, see the Chlorination of Methyl Formate thread and its references.

A more contemporary method is to use AIBN as FR initiator rather than dibenzoyl peroxide.

These are alternatives to photocatalyzed direct chlorination.

Main problem is pretty much same:

Where will you get your sulfuryl chloride? In most countries (mine included) you can't buy it. You can make it but you need oodles of DRY chlorine and so you are in the Cl2 generating biz and with an elaborate drying train betwixt generator and reactor to scrub the water. In the case of SO2Cl2 you can also expect to need a tank of SO2, or another gas generator with its own and different drying train. You then pass both gases over catalyst (proper grade of GAC) in a cooled tube, as reaction is exothermic. You can make maybe half a liter of sulfuryl chloride a day with this setup.

Sulfuryl chloride and its vapors attack the skin and eyes, you will need to protect yourself with fume hood, gloves, mask, etc.

This entire technique is pertinent neither to acid anhydrides nor acid chlorides as you will see when you study the articles. Thanks for the papers, they are useful but not for acetic anhydride. You might consider starting a free-radical chlorination thread or joining Organikum's thread on toluene chlorination which can be done this way.
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Sulfuryl chloride can be prepared by an easier, discontinuous method, using camphor as catalyst. Look in Sartoris "The War Gases".

Free radical chlorination of hydrocarbons like toluene with sulfuryl chloride is well known and described even in my old Organikum book.

But I wonder what happens if one reacts sulfuryl chloride with e.g. sodium acetate? Sulfuryl chloride is an acyl halide in itself, although one of relatively low reactivity.

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Sauron
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Camphor indeed catalyzes the rxn of Cl2 and SO2 but both still need to be in well dried condition or the moisture will destroy the sulfuryl chloride as fast as it forms.

Also quite a bit of product ends up trapped in the camphor. It's a mess. The GAC (granulated activated carbon) process is better and as soon as you have a few hundred mls of SO2Cl2 can be run very advantageously as a loop reactor with the sulfuryl chloride acting as a solvent for the gases being introduced. The reaction tube is water jacketed to remove heat of reaction, otherwise the GAC turns into CCl4.

The advantage of the loop reactor (using peristaltic pumps with PTFE heads and PTFE tubing because sulfuryl chloride desroys Viton rather rapidly) is that you can run with excess SO2 or excess Cl2 and then at the end, just shut off the component that is in excess. If SO2 is in excess then add Cl2 slowly till the product turns a very pale yellow-green, signalling that Cl2 is now in slight excess. If Cl2 is in excess then shut it off and slowlyadmit SO2 till the pale gren color disappears.

I have a US patent file that does all this on a bench scale with Masterflex pumps, a UV-Vis to monitor the color at peak for Cl2, and mass flow controllers to control the stoichiometry of the gases. I have everything to do this now except for the MFCs. Those have to be calibrated for the specific gases and set for pressures just over 1 atm to work with a gas generator rather than gas cylinders. Anyway the MFCs are not necessary, as mentioned the process works fine with one component in excess. More important is controlling the rate of gas production which I do by controlling the feed to the gas generator using again, peristaltic pumps. Altogether it is a pretty elaborate setup but it will reliably turn out about 60 ml an hours of sulfuryl chloride so how much do you need?

I talked two or three AC sellers out of about a dozen half-Kg samples of GACs of appropriate sizes and types. Cost me nothing. The dozen or so Masterflex pump drives and heads I have came off LabX cheap, and only three are require for this setup. One is a PTFE diaphragm pump and the others are peristaltic pumps to move much less agressive fluids for the gas generators. Very mundane tubing handles conc HCl with impunity. It's only the sulfuryl chloride that is a bitch. But PTFE shrugs it off.

This takes a rather large hood to do, what with three pumps, and the colorimeter, the CSLR and reactor tube, and connections out to recirculating chiller. It's the hood that is holding me up. A 2.5 meter wide 1 meter deep hood. I do expect to have this installed before the end of the year. I'll post pics of the hood and this setup at that time.

Maybe I can set up the CSLR and tube and colorimeter in my glove box and feed the Cl2 and SO2 from generators and drying trains outside the box. The glove box is here already. This could be set up much sooner. The box would be sufficient barrier to protect me from the SO2Cl2 so why not? It's a big old Labconco.

Would you care to see the patent?

[Edited on 2-6-2007 by Sauron]

Attachment: 5498400[2].pdf (444kB)

tupence_hapeny
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Hang on,

If the peroxide-catalyzed chlorination of toluene proceeds effectively the same as the photo-induced chlorination of toluene (which it appears to do - barring the solvent effect) and the product of each - firstly benzyl chloride, then benzodichloride then benzotrichloride are the same - whether achieved with SO2Cl2/Peroxide or Cl2/UV - then it should be possible to di & trichlorinate the initial benzyl chloride simply by adding additional chlorinating agent (& perhaps additional catalyst?)?

I suggest that TCCA (once again, apologies to those offended by the continued reference to this widely available and useful chemical) could be used instead. This has even been mentioned (in a vague way) by someone here (insofar as using an excess of toluene it should be possible to keep the percentage of di/trichlor down).

As to whether this is on or off topic, I hesitate to call it - simply because fully half of the posts here deal with the usefulness and synthesis of a variety of halogenating agents - to the extent that they produce the AcCl which is then turned into Ac2O in-situ... I would regard it as being particularly unfair if I am called for being off-topic in relation to the original post - when 'most' of the posters to this topic have been similarly off topic.

tup

PS I am interested in this precisely because TCCA is so widely available (as is toluene) and such a route would provide direct access to Ac2O without seriously expensive chlorinating agents (which could also be prepared via benzotrichloride)... Imagine - highly sought after & seriously restricted chemicals becoming widely available?

PPS Sauron, before you say it, where this was discussed earlier, alternative solvents were provided, and other members of this forum provided details of their results using TCCA for the preparation of benzyl chloride (in which reaction TCCA is used a virtual replacement for sulfuryl chloride) - so this MIGHT work - I cannot say for certain that it will.

[Edited on 2-6-2007 by tupence_hapeny]

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Sauron
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The only relevance of your posts to THIS thread is the rather distant one that benzotrichloride can be employed to make phthaloyl chloride which can be in turn utilized to make acyl chlorides and thus acid anhydrides.

TCCA and sulfuryl chloride are mechanistically very different.

Chemically and structurally totally different. And benzyl chloride is NOT a subject of this thread, benzoyl chloride is (slightly) but those are two different compounds. And you don't make benzoyl chloride with TCCA.

So IMO you remain OT here, and you should start your own thread or move this material to Organikum's thread which DOES deal with free radical chlorination.
tupence_hapeny
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Right,

Is this still off-topic (in my view, NO it is not, may not work - fuck knows why - but it ain't off topic - BTW how fucking OTC would that be?).

As to sulfuryl chloride, here are a series of three articles on the subject by McKee & Salls, in the first - they deal with the production of sulfuryl chloride using activated charcoal - the biggest problem being the condensation of the same - was solved by using the chlorosulfonic acid generated in-situ by reaction of some of the as formed sulfonyl chloride with water - which then dissolves more SO2 & Cl2 (+SO2Cl2) improving the yield. Note that one of the earlier processes used glacial acetic acid - probably making AA in-situ, as AA was also used to condense the shit...

If not, simple addition of benzoyl peroxide to the final mixture would solve that problem (provided NaAc was added as well).

In the second paper they deal with making the sulfuryl chloride by reacting liquid chlorine & liquid sulfur dioxide (low temps are a must) and using the SO2Cl2 as a solvent for the resultant mix of Cl2/SO2 & SO2Cl2. Apparently GAA could also be used as a solvent...(may not be in this paper - I cant remember).

The third paper deals with the hydrolysis of SO2Cl2 to give hydrochloric and sulfuric acids... It is therefore off-topic, but mentioned all the same simply to provide the remainder of the necessary information.

PS Do you seriously dispute the fact that the majority of posts on this topic has been similarly off-topic?

EDIT BY POLVERONE: DO NOT DIRECTLY LINK TO ARTICLES WITH THE JACS TRICK. IT WILL HASTEN THE ARRIVAL OF THE DAY THAT ROUTE IS CUT OFF FOR ALL OF US.

[Edited on 6-2-2007 by Polverone]

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Eclectic
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Hey $0.025, I don't really care about the oxidation of acetaldehyde, cause scavenging the water formed in the reaction is problematic (although 3A molecular sieve in the reactor...), but could you post the article on the last page re. CS2 in the making carbon disulfide thread? Nevermind. All you have to do is change the last few characters in the above link from *024.pdf to *025.pdf. [Edited on 6-2-2007 by Eclectic] tupence_hapeny Hazard to Others Posts: 131 Registered: 25-3-2007 Member Is Offline Mood: continuing respiration (touch wood)  Quote: EDIT BY POLVERONE: DO NOT DIRECTLY LINK TO ARTICLES WITH THE JACS TRICK. IT WILL HASTEN THE DAY THAT ROUTE IS CUT OFF FOR ALL OF US. Sorry... I will download & link to a share-provider - suitably chastened & will not recur. NOTE Sulfuryl chloride will not, either directly or with the aid of benzoyl peroxide, chlorinate acetic acid... This was wrong, as even a momentary perusal of Brown's article on chlorinations with benzoyl peroxide will show. Thus, unfortunately, a simple route is cut off.... On the other hand, another step is possible - condense the SO2Cl2 (with minimal SO2 & Cl2 dissolved in it) in the chlorosulfonic acid - distill off the sulfuryl chloride and pass that into a vessel containing Toluene & benzoyl peroxide. From the benzoyl peroxide make an agent that will chlorinate the acetic acid. Major fuck around, I know, but I see no easier (OTC) way there, on the other hand - I have always wanted thionyl chloride but certainly am not allowed to buy it - so that is the long and the short of it unfortunately... tup We are all the sum of our experiences, and our reactions to the same Sauron International Hazard Posts: 5351 Registered: 22-12-2006 Location: Barad-Dur, Mordor Member Is Offline Mood: metastable Thionyl chloride is inappropriate for chlorinating acetic and propionic acids because the bp's of those acyl chlorides are too proximate to that of the thionyl chloride (always used in excess) and therefore, the reaction mixture is too hard to seperate. See Vogel. So the fact that you can't get thionyl chloride, is immaterial to the acetic anhydride/acetyl chloride and propionyl chloride problem. This point has been emphasized and re-emphasized several times in the last 12 pages of this thread. Some of us can buy thionyl chloride (but not me, and not you.) It's a useful reagent for most acid chlorides, just not the lower few. tupence_hapeny Hazard to Others Posts: 131 Registered: 25-3-2007 Member Is Offline Mood: continuing respiration (touch wood)  Quote: Sauron Said Thionyl chloride is inappropriate for chlorinating acetic and propionic acids because the bp's of those acyl chlorides are too proximate to that of the thionyl chloride (always used in excess) and therefore, the reaction mixture is too hard to seperate. See Vogel. So the fact that you can't get thionyl chloride, is immaterial to the acetic anhydride/acetyl chloride and propionyl chloride problem. This point has been emphasized and re-emphasized several times in the last 12 pages of this thread. Some of us can buy thionyl chloride (but not me, and not you.) It's a useful reagent for most acid chlorides, just not the lower few. For acetic anhydride I would actually prefer phthaloyl chloride, I have details of the reactions with it for one thing... I have (for some bizarre and fucked up 'psyche' reason probably) actually always wanted thionyl chloride, in fact I would probably if ever given the choice take a liter of that over a liter of AA if someone wanted to sell it (Fat Fucking Chance). Consequently my musing at the end... Ummm, would it be sufficient in future when citing JAC/JOC simply to give a link to the abstract? Or should I not even do that? Perhaps just provide the citation in full? tup We are all the sum of our experiences, and our reactions to the same Sauron International Hazard Posts: 5351 Registered: 22-12-2006 Location: Barad-Dur, Mordor Member Is Offline Mood: metastable Thionyl chloride is relatively hard to make (relative to sulfuryl chloride.) This is because you need SO3 or 65% oleum to do it, and that is expensive stuff and a bitch to handle. See Brauer on thionyl chloride lab prep. Thionyl chloride has been so demonized that many countries simply ban its import without a special permit. In this country I also can't buy SO3, although I can buy oleum, up to 65% and have done so but it was very costly. How costly?$750 US a liter. OK bear in mind that a liter of 65% oleum is 2 Kg and that 65% of that 2 Kg is SO3 so it's about 50 cents a gram based on SO3. Ouch.

For the same reasons chlorosulfonic acid is a problem. The MOD restricts it and in order to make it you need SO3 or oleum and big brass balls, because running dry HCl into high percentage oleum is very exothermic.

There's another way to make chlorosulfonic acid, from sulfuryl chloride, using Hg salts, and this would probably be the way to go.

But back on topic:

Phthaloyl chloride does work, but it doesn't work any better than benzoyl chloride for making acetyl chloride and it is more expensive. If you make your own phthaloyl chloride you can get the cost down to about the same as that of benzotl chloride. You make it from phthalic anhydride and benzotrichloride.

Making your own benzoyl chloride does not achieve any similar economy because the cost of sodium benzoate is rather high. It actually costs as much as benzoyl chloride.

For those who can't purchase TCT, benzoyl chloride is the best choice for a reagent to prepare acetyl chloride. Second best if you make your own is phthaloyl chloride. But if you can get TCT do so because it is far cheaper than either.
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 Quote: Originally posted by tupence_hapeny Ummm, would it be sufficient in future when citing JAC/JOC simply to give a link to the abstract? Or should I not even do that? Perhaps just provide the citation in full? tup

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A number of methods have been discussed regarding preparation of Acetic Anhydride. Out of all of these which method is the easiest to be tried in the lab. I'll appreciate if some one could send pictures of the setup of the apparatus.

Are all the reagents discussed in this method easily available.