04-19-02 09:16
No 299041
For the reaction: GAA + xS + yCl2 __> Product,
under exactly what conditions (x,y, temp, catalyst, etc.) is the product,
a) Monochloroacetic acid (MCA)
b) Acetyl Chloride (AC)
c) Acetic Anhydride (AA) ?
In Post 208698 (Antoncho: "Re: Vilsmeier mechanism: the alternatives to POCl3", Chemistry Discourse), Antoncho says MCA is formed under reflux and in 'less vigorous' conditions, AC is the product. Any idea of what these 'conditions' are, Antoncho ? Anybody ?
For obvious reasons option (c) is quite interesting and I wouldn't have thought it likely except that Patent GB211167 claims it can be done with an 'excellent yield' of AA. However, after reading the patent a few times, I'm still having trouble figuring out exactly what makes their process give AA rather than AC or MCA.
(Hive Bee)
04-19-02 10:15
No 299048
Acetyl Chloride and acetic acid will give you acetic anhydride. I'm sure boiling acetic acid in thionylchloride will do the trick as well.
(Stranger)
04-20-02 04:45
No 299375
The AA synth from NaOAc, S and Br2 on R's page is easy and works greeat. I'm sure Cl2 could bee substituted for Br2...
Azarius
(Hive Bee)
04-23-02 07:49
No 300364
Hest:
I don't have AC. I need either AC or AA. My last SOCl2 was used up making AC from acetic acid (which is btw quite an endothermic reaction), but all was lost due to suck back of water from the gas absorber.
Azarius:
Although Br2 is available, it seems too valuable to me to be used on reagent preparation, unless it were in catalytic quantities. Cl2 can be substituted but the synth requires some AA to be present initially. (Actually I've tried it but the outcome is not clear at this stage..)
I'm puzzled that my post only got two responses (thanks Hest & Azarius) but the number of views is 100+. I would think more bees would have something to say regarding OTC Acetic Anhydride or OTC Acetyl Chloride...?
(Old P2P Cook)
04-23-02 07:55
No 300368
If you want OTC acetic anhydride then I would think that you would use the ketene process.
(Hive Bee)
04-23-02 15:23
No 300435
Terbium:
Although the ketene process is elegant, I have no wish to fuck with such a toxic substance, or start constructing specialized equipment(*). Judging by my history of handling Cl2 it would just be looking for trouble.
It has been recommended as the answer to OTC AA by a number of bees, but I wonder how many of them have actually done it completely DIY (other than Hypo).
However, although I do appreciate the responses received, so far nobody has or is willing to answer the question posed by my original post.
* But by now I've learnt that I should never say never..
(Official Hive Translator)
04-23-02 18:00
No 300457
Sorry for not replying earlier, i just missed this post.
so...
I suggest you stick to the S-and-Cl2 and Na acetate route described in that another (UTFSE) post of mine now archived on Rhodium's - i copied it verbatim from a good old chembook.
Chloroacetic acid is formed when AcOH is boiled in light w/S or red P and bubbling chlorine. Chloroacetyl chloride is also formed. This reaction, i believe, proceeds via a free-radical mechanism.
If no catalyst is used, only acetyl chloride forms under the same conditions. However, it quickly reacts w/the acid to form anhydride.
If the reaction of sulfur, chlorine and sodium salt of AcOH is performed under milder conditions, however, the mechanism is altogether different. First disulfur dichloride is formed from rxn of sulfur and chlorine. Then S2Cl2 reacts w/NaAcO to form NaCl and acetyl disulfide. The latter is unstable and decomposes at ~80-90 C to AcOAc, SO2 and 3 sulfurs.
I hope that answers your question, oh thou, the exquisite flower of the faraway misty cliffs...
Antoncho
P.S. Oh, yeah. BTW. By now constructing new equipment has beecome SWIM's second name
- this not only develops one's imagination and technical and creative skills, but also makes life gradually more and more pleasant, as the said equipment accumulates and begins to pay back for the efforts spent in making it. Really.(Hive Bee)
04-24-02 09:43
No 300724
Antoncho:
Yes thank you, that's exactly the kind of info I was looking for - you're the man.
Now,
I suggest you stick to the S-and-Cl2 and Na acetate route described in that another (UTFSE) post of mine now archived on Rhodium's
I tried this and it appeared to work, although not very well. Where I deviated (yes I'm a deviant) from the method was allowing the decomposition of acetyl disulfide at atmospheric pressure rather than vacuum. So once I get my aspirator station behaving itself I'll try it again (and oh yeah I've got to make more NaOAc first..damn) which brings me to the other point,
By now constructing new equipment has beecome SWIM's second name - this not only develops one's imagination and technical and creative skills, but also makes life gradually more and more pleasant, as the said equipment accumulates and begins to pay back for the efforts spent in making it. Really.
I completely agree but by now my 'lab' is littered with the corpses of equipment that didn't quite work (H2 generators, Cl2 generators, vacuum devices, stirring devices, etc.) and I'd like something to work in simple glassware for a change.
Jeez this is turning into a very long dream...
(Hive Bee)
04-24-02 10:18
No 300734
M_G I wish I could mail you 5L of AA, this is a waste of your skil's and time.
(Stoni's sexual toy)
04-24-02 10:52
No 300746
Acetic anhydride is such a common chemical and used in such big quantities that depending on your local laws it might not be difficult and dangerous at all to order it when you are affiliated with a university or a company. It's not difficult either to come up with or find an established (e.g. analytical) procedure which absolutely requires this chemical. Every lab I've seen so far had a bottle of AA, this substance being controlled is another example of wishful thinking on the side of the authorities. It simply will not happen. They don't have the manpower to even collect the names of all legitimate users of AA *). I even ordered AA under my real name without giving my phone number or address before in a country which specifically says that every purchase of AA has to be reported, and nothing whatsoever happened. If the Men in Black would have showed up to question me I would have simply laughed in their faces and given them a 3 pages long list of legal uses for the AA and told them to quit harassing me like this.
*) obviously doesn't apply to the US where the government prefers to spend 40 billions a year on the war on drugs instead of using the money for something useful instead.
I'm not fat just horizontally disproportionate.
(Chief Bee)
04-24-02 14:51
No 300786
I even ordered AA under my real name without giving my phone number or address before in a country which specifically says that every purchase of AA has to be reported, and nothing whatsoever happened.
Ditto here, in another european country. More than once from different suppliers, young and innocent. Intention: RDX.
(Stoni's sexual toy)
04-25-02 10:45
No 301179
Still, a note of caution.
What worked for us years ago will not necessarily work for you today. Use your brain when you attempt anything like that. Have a good reason why you need the AA, use common sense and check your local laws.
I'm not fat just horizontally disproportionate.
(Newbee)
04-25-02 12:58
No 301206
Yes osmium, you're right. AA is a scheduled precursor (class II), EU-Order Nr. 3677/90 from december 13th, 1990. All transcations must be recorded and reported before shipping. Be careful, undercover investigations are common at least here in germany
!
(Stranger)
04-27-02 11:18
No 302042
Ditto here, in another european country. More than once from different suppliers, young and innocent. Intention: RDX.
I rung up the customs office when I was 14 asking them if it was ok to import AA (also with intention of RDX) for general laboratory use. They said it was fine. They asked me what I wanted the methylamine for though (Intention: MMAN).
Azarius
(Stranger)
05-01-02 21:40
No 303887
Although the ketene process is elegant, I have no wish to fuck with such a toxic substance, or start constructing specialized equipment(*).
This wannabee found that generating ketene was easy as could be, although flicking the switch to the nichrome wire was nerve racking. All-in-all, it was suprisingly easy to handle this noxious gas with proper glassware and good ventillation. Regrettably the wire heated up so much that the stopper was breaking down in the claisen adapter and no solution was ever pursued.
If you can't obtain acetic anhydride through the regular means of acquisition... give it a go!
improving the bowel movements of cats & dogs everywhere...