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chemicalpower
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mrSauron If you think that J got Acetyl chloride then why is the colour light yellow How much time do you think is needed For the reflux reaction to
complete I refluxed For 8 hours and then left the mix to cool overnight in morning a white precipitate had settled and the colour was Transparent I
Fractionated the liquid and Collected a Liquid at 75 degrees. I mean to ask how much time is required for the fractionating as I Think I hurried
because no or unoticABlE liquid came at 55 degrees further Should I refractionate the liquid once again
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Sauron
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It would not hurt to refractionate the product.
How are you measuring the temperature? And where?
Bath temperature, liquid temperature, vapor temperature in pot, vapor temperature at top of column?
Do the fractionation SLOWLY, allowing several hours at 100% reflux to equilibrate system. Then start collecting at a high reflux ratio, at least 10
drops returning to column for every drop taken off.
In this fashion you should see an accurate boiling point of acetyl chloride 51 C.
Don't worry about color. Light yellow is OK.
NO OTHER PRODUCT IS POSSIBLE THAN AcCl.
It isn't AcOH bp 117 and it certainly isn't Ac2O bp 140.
So most likely you are just doing the fractionation fast and you are getting AcCl and a little AcOH and bp is therefore a little high.
---------
As to making the AcCl: the literature source was vague, it was just a suggestion in the book "S-Triazines and Derivatives" by Smolin and Rapaport, amd
it said that "long refluxing of cyanuric chloride in a large excess of glacial acetic acid is a good way to make cyanuric acid" The acetyl chloride
is by product. The precipitate is cyanuric acid.
So, the 8 hours was my idea but it could be shorter or it could be longer, if I were you I would try 8 hours, 16 hours and 24 hours (using same
amounts of CC and AcOH each time) REFLUX, that means BOILING all that time. Compares how much product you get at each reaction time. When you get 100%
of the theoretical amount you can stop increasing the time. If you get close enough say 90-95% you can also stop increasing time if you want.
Remember you do not want AcCl to escape through condenser. So you keep reducing the heat as more and more AcCl forms so that all AcCl condenses in
first half (bottom half) of condenser, you can see where this is happening.
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chemicalpower
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i am measuring the temperature at the top of the fractionating column i guess the vapour temp.i will do the reflux for 16hrs now
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Sauron
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Just remember to do the fractionation as slowly as you can stand to.
And don't let AcCl get out of the condenser during reflux.
As AcCl increases and AcOH decreases a little, bp will fall.
So heat input is slowly brought down to compensate
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Sauron
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Not yet. I have requested quote for VA, and I have purchased a pressure reactor in case the reaction requires that (it could just as easily require
vacuum.) When I have any results I will post them here.
Meanwhile @chemicalpower is making very good progress with solventless chlorination of acetic acid to acetyl chloride with TCT as suggested in
"S-Triazines and Derivatives" by Smolin & Rapaport. He is now working on optimizing reflux time vs yield.
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chemicalpower
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ok i have increaed the reflux time to 14hrs seems to be correct.but i just found outthe sodium acetate i have been using is trihydrate form not
anhydrous.and anhydrous is not available here.what do i do about tht is there anyway to convert trihydrate to anhydrous sodium acetate.
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Sauron
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You heat the trihydrate in a drying oven (with the trihydrate in a large evaporation whish of shallow porcelein) at @125 C and the water is driven
off. Break up the fused acetate into powder and immediately use it. Otherwise it simply readsorbs water from the air and reverts to trihydrate.
Frankly you need to do this even if you can buy "anhydrous" NaOAc because it is seldom anhydrous enough.
However, why worry about NaOAc? You can react AcCl with glacial AcOH in presence of a tertiary amine (like triethylamine) to obtain Ac2O.
And since you already have AcOH this is better.
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not_important
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Note that when fusing sodium acetate you do not want the temperature to rise too high or it will decompose. I think that 150 C is about the very
hottest you should allow the aceate to reach.
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Sauron
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Yes, that's why I specified 125 C. A drying over usually has ventilation option, and temp control. I use a Memmert oven with both. You can track the
extent of drying by weight loss. Tare the evaporating dish, and used a weighed amount of the trihydrate. You will lose three moles of water per mol of
the trihydrate, that is a loss of 54 g per mol.
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Sauron
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I do not advise heating above 125 as you will inevitably get some decomposition.
It takes longer but is less wasteful.
You really need a dedicated drying oven designed for chemical applications.
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UnintentionalChaos
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Red phosphorus is a stabilized form of phosphorus. It is still pure, but unlike white phosphorus, it wont combust spontaneously in air, spreading
clouds of P2O5 into every crevice of your workspace.
It will react just fine for what you need it to.
[Edited on 4-25-07 by UnintentionalChaos]
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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Sauron
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Phosphorus will do nothing for you in this reaction.
PCl3 or PBr3 might but you do not get those from P and HCl or HBr
You get those from P and Cl2 or Br 2
Don't waste your time. When I have results I will let everyone know.
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chemicalpowerII
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dear mr sauron,
i refluxed the mix for 16 hours and the white precipitate settled down. then i filtered the precipitatae out and fractionated the liquid, once at
100degrees. then the second time at 55degrees. everything seems as expected. the fractionation column behaved nicely and the temp at the top was easy
to keep at 55 degrees and about 450cc distilled over. now the sodium acetate is hard to make anhydrous and i when i heat it at 120degrees for half an
hour and then mix with the liquid ( presumably acetyl chloride) it gives a clear liquid with similar smell to acetic acid rather a little more pungent
and chlorine smelling.
but it fails all test , like it mixes in water on contact, is not combustable
tommorow i will try the TEA method.
isnt acetyl chloride conbustable.
to satisfy my curiosity i tried to refractionate the liquid for the third time, but as soon as the evaporation cloud reaches the top the temperature
rises to 110 degrees , if it were acetyl chloride it should fractionally distill over at 55 degrees or so, whats going on here
by the way i changed my log in name because i lost my previous password and it wasnt sent to the email so i re registered
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Sauron
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I'd guess you did not dry the sodium acetate well enough, half an hour is nowhere near long enough.
There the water of hydration remaining in the sodium acetate simply converted your acetyl chloride - unquestionably that is what was distilling at 55
C - to AcOH and wasted it.
And that is why the sodium acetate must be thoroughly dried.
Good luck with the AcOH/AcCl/TEA method.
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chemicalpowerII
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ok i tried the TEA acetyllchloride method when i mixed the TEA acetic acid and acetyl chloride drop by drop the mix started heating up and i kept it
under reflux.but i forgot to filter the teachloride out and started fractionating have fractionated a little liquid yet and have a dark brown liquid
in the reaction flask dont know what will come out of it any ideas
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Sauron
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What was vapor temperature of product at top of column?
If 140 C then Ac2O
Dark brown liquid in pot is TEA, amines oxidize readily and turn dark which is why we distill them before use.
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chemicalpowerII
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i have again started the acetic acid cc process fot acetyl chloride. mr. sauron what is the pungent gas that escapes out even though the temperature
at the top of the reflux condenser is 30degrees smells like hcl to me
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Sauron
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And I am still waiting for vinyl acetate to arrive. I think it may take substantial experimentation before find the right combination of variables
described in that cursed patent (if any) that will work. Catalyst, pressure vs normal vs vacuum, etc.
You can disregard everything chemicalpower has said because he never obtained any TCT. What he thought was TCT (CC) was cyanuric acid. Not cyanuric
chloride! And later all he could find was TCCA (trichloroisocyanuric acid) which is totally different and will not do same job. So all of his posts
are worthless.
You at least have a cheap source of AcCl in bulk, and you have the capability to dry NaOAc in quantity. You just have to fix a few small details in
the handling of the AcCl and in the fusing of the acetate salt. So you still have a good workable method at hand. Use it.
When I have anything to report about the VA method (good or bad) I will post it here.
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chemicalpowerII
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what will happen if he keep a mixture of acetic anhydride +acetic acid at 10degrees temp or below that. would the aceticacid glacial form crystals and
can the anhydride be poured out.
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Sauron
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Phosphoris acid,
However you will have a very hard time seperating the acetyl chloride from the phosphorus compounds, the PCl3 is quite expensive, so are PCl5 and
POCl3.
If you want to look at alternate chlorinating agents look at benzoyl chloride and phthaloyl chloride if available in your country.
But I think you already said you can't get them? Or was that the fellow in Pakistan? I don't remember.
No news yet on VA method, sorry.
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garage chemist
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Lets say one was building a 1000°C max. tube furnace with a 25mm quartz tube, would it be possible to generate useable quantities of ketene and react
them to AA by heating the furnace to 750°C and slowly distilling acetone into one end of the pipe?
At the other end, the product gas would pass through a condenser with ice-water to condense unreacted acetone and then through a washing bottle with
glacial acetic acid.
I am in the process of building an electric tube furnace, and when finished would like to try ketene/AA production just to see if it is possible. The
furnace would predominantly be used for synthesis of carbon disulfide if that works and the technical difficulties (most importantly getting
temperature-resistant gastight connections to the quartz tube) can be overcome.
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Organikum
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IIRC in the acetic anhydride thread is a post of mine, which names a patent which explains in detail the construction of an apparatus which produces
ketene from acetone.
It consists mainly of a coppertube of 70cm length with 3mm inner diameter, which is in a zone of about 10cm to the end heated to 700°C to 800°C.
Then the formed ketene is vented into acetic acid to be cooled rapidly and to form the AA.
The beauty of the patent is that it names exact temperatures, flow rates etc. something rarely found otherwise.
Another nice aspect is that such a 3mm tube is simply safe from explosion and flameback.
Temperature control in the hot zone is an issue - I suggest to lead the thin copper tube trough a big junk of metal and to heat this with a
temperature sensor between tube and metal.
Rapid cooling of the formed ketene is essential or it will polymerize, an issue the ketene lamps all have.
/ORG
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S.C. Wack
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JACS 47, 1427 (1925):
Summary
An improved apparatus for the preparation of ketene from acetone is
described. The temperature, the rate of flow of acetone, and the percentage
decomposition of acetone all influence the yield of ketene.
For practical purposes, the following conditions seem best for ketene
production: temperature, 695-705°; rate of flow of acetone, 5 cc. per
minute, and the decomposition of acetone, between 25 and 40% of that
introduced. These conditions give consistent yields of ketene which range
between 35 and 45%.
The glass combustion tube becomes stratified after it has served in a number
of runs. No ketene results when the glass tube is replaced by an iron
pipe. Carbonization occurs instead, at temperatures which would allow
ketene production.
JACS 56, 1760 (1934):
...Below 600° the yield of ketene shows a
measurable diminution but above 600° the effect
of changing the temperature is not much greater
than our experimental error; we have verified
this up to temperatures of about 900°. We also
find that the temperature of the decomposition,
provided it is above 600°, is only at best a second
order effect compared with the effect of the extent
of the decomposition of the acetone...
Summary
In order to obtain good yields of ketene from
acetone it seems to be essential to decompose only
a small fraction of the acetone. Factors such as
the temperature of decomposition (provided it is
not much below 600°), time in the furnace and the
presence of inert gases do not appear to have any
very appreciable effect on the yield of ketene
except in so far as they affect the fraction of
acetone decomposed...
[Edited on 12-6-2007 by S.C. Wack]
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Sauron
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The literature of ketene generation is extensive and subject of a CR article which I posted early on in this thread.
If you examine and cross-compare the reliable checked methods the tube furnaces do not compare well to ketene lamps, the former producing about a
quarter of a mol an hour compared to half a mol for the ketene lamp. The tube furnaces generally required rather long heated zones. My tube furnace is
2" x 12" while the one described in Org.Syn is more like 20" long which certainly speaks to the vapor residence time in the furnace.
The lamps' achilles heel is carbonization of filament requiring cleaning so spare filament assemblies are called for, increasing apparatus cost.
All in all I do not think this is a fruitful line of inquiry at least not for Ac2O prep for which better methods are at hand.
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S.C. Wack
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If one has a working tube furnace, I don't see how it cannot be fruitful. It can gather dust or be put into service. The electric furnace core in the
first quote that I posted (by the same author as in the OS page) was 3 X 80 cm btw. No mention of glass tube diameter, and no mention of apparatus in
the second quote - other than the tubes were quartz and did and didn't contain broken quartz or pyrex. Just giving the helpful hint of the ketene
getting carried away by excess acetone vapor.
[Edited on 13-6-2007 by S.C. Wack]
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