conducter
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Lead Acetate distillation with PAA
I was wondering if anyone has a procedural writeup of how to do this or at least some tips.
From what i know all one has to do is heat Lead Acetate and Phenylacetic acid and the distillate that comes over will be Benzyl Methyl Ketone (p2p)
because the lead acetate is turned into Acetic Anhydride in situ.
ive read rhodiums page as well as others but cant seem to find a detail on ratios or what temp to react at for how long or anything
Actually i believe that lead acetate should be to 3:1 ratio to PAA but any help would be nice.
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guy
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Lead acetate turns to acetic anhydride?
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chemrox
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For the preparation of the reagent in question: http://www.crscientific.com/leadacetate.html
If the desired result is acetic anhydride, why not go directly there? There are numerous threads and posts with methods for it available.
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conducter
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http://designer-drug.com/pte/12.162.180.114/dcd/chemistry/p2...
scroll down to Route 1B, the Reaction of Phenylacetic Acid with Lead(II)Acetate
it says and i quote...
"The in situ formation of acetic anhydride from the heating of lead(II)acetate will result in by-products identical to those produced through Route 1A
by the described Dakin-West, Perkin, and aldol condensation reactions"
Question: If the desired result is acetic anhydride, why not go directly there? There are numerous threads and posts with methods for it available.
Answer: The acetic anhydride is not the desired product. P2P via the distillation of lead acetate with Phenylacetic acid results in P2P. The reason
this way is interesting to me is that AA is very hard to obtain without ketene or ketene lamp. And lead acetate is very easily obtained.
[Edited on 23-2-2007 by conducter]
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garage chemist
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Heating dry silver acetate results in acetic anhydride distilling off, according to the admin of the german chemistry forum.
Argh, I could hit myself for not posting this in the acetic anhydride thread!
This seems to be a very viable method for smallscale preparation of Ac2O. The silver can be recycled over and over, and you dont even need GAA. Even
vinegar would theoretically do the job, of course with extensive boiling down of the silver acetate solution (precipitate Ag2O from a silver nitrate
solution with NaOH, filter off, and dissolve in acetic acid).
Too bad the residue is silver and not Ag2O, because silver oxide decomposes so easily, so for recycling, you need to dissolve it in HNO3 and
precipitate Ag2O with NaOH.
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S.C. Wack
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And the source for this statement is? Experience? Some blurb in a book? Is this simple distillation? The JACS article uses inert gas sweeping, which
is often necessary to get yields of desired pyrolysis products from salts. Yield 600 mg on heating 2.1 g at 300-400C 2-1/2 hrs.
There is much mention of silver acetate (two RSC CS2 articles, patent, Ber. article, Soviet article) copper acetates (patents, Soviet article), and Al
acetates (Soviet article), but the only mention of lead that I've seen is the JCS article that I posted earlier in the appropriate thread. The JFS
article does not say (i.e. present evidence) that the anhydride is formed, regardless of the quote.
The other refs above:
DE556247
US2073686
Proc. Chem. Soc. 20 (1957)
Zhur. Neorg. Khim. 5, 558 (1960)
Izv. Akad. Nauk SSSR, Otd. Khim. Nauk 1003-1011 (1963)
Ber. 69B, 2152 (1936)
[Edited on 25-2-2007 by S.C. Wack]
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Organikum
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For conveniant production of lead(II)salts of carboxylic acids look for chemoleos posts here:
http://www.sciencemadness.org/talk/viewthread.php?tid=5490
Otherwise the salts can prepared from litharge and the carboxylic acid, the acid should just not be too concentrated. <60% strength for acetic acid
as an example.
Pyrolysis with decarboxylation sweeps itself with CO2 and for those reactions involving the thermal decomposition of salts I encounterd comparable
simple tweaks are possible which avoid sweeping with inert gas. Either by modifying the setup (enhanced heat transfer for example) or by using other
salts, additional catalysts or whatever.
This must not be valid for ALL reactions, thats understood, but it for sure is worth a shot or three before giving up before even starting just
because in some article they had to use inert gas and do secret stomp dances around the flask to get it going.
Is only my opinion, what else.
/ORG
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Sauron
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If you look far enough back in Chemical Abstracts in the 1920s there is a description of the dry distillation of phenylacetic acid and lead acetate to
produce P2P.
The abstract was from a Japanese forensics journal or maybe a pharm journal, at that time amphetamines were a huge clandestine product in Japan as
people took them so they could work longer hours (much like long haul truckers did in the 50s and 60s) and this method was a fave among Japanese bent
chemists at the time.
I did this reaction many times c.30 years ago and found that it worked very well at the scale indicated in CA but, did not scale up very well.
A few caveats:
1. You can expect to throw away your flask after every batch as there is no way I ever found to get the large amount of solid residue out of there.
2. You will need very efficient condensrs. I used a Friedrichs with a long West in series. When the ketone finally comes it come hot and angry and
FAST and if you don't have a good setup you will lose some.
3. Carefully fractionate your product, preferably in vacuo.
I only used one other method, to make P2P, back then and that was a malonic acid synthesis of the ketone starting with phenylacetyl chloride. Much
SOCl2 died for my sins. This method scales better, and is more elegant than the lead acetate method. These days most people will have trouble getting
thionyl chloride so either TCT or benzoyl chloride is the better way to go to prepare the requisite acid chloride of phenylacetic acid. TCT is cheaper
and more efficient since it has 2-3 times the active Cl of benzoyl chloride per mol and benzoyl chloride is used (her the HC Brown method) in 2:3 or
1:2 excess.
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Organikum
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For scaling up look here:
http://www.erowid.org/archive/rhodium/chemistry/p2p.paa-pb.h...
[Edited on 15-5-2007 by Organikum]
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Sauron
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That would have been nice to read c.1977 but, I left all that behind me while Jimmy Carter was still president.
And I still think the malonic ester route from phenylacetyl chloride is better. For one thing, you don't have to deal with Pb-compound contamination
in the P2P and further down the road.
At that time P2P was just another ketone, not the Sch 1 controlled substance it is today. The DEA did not yet exist as such; it was in its short lived
transitional marriage between the old Bureau of Narcotics frin Treasury and the Bureau of Drug Abuse Control from the FDA (who didn't even have police
powers) and was called the Bureau of Narcotics & Dangerous Drugs.
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tupence_hapeny
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I've seen numerous people state that iron salts work better, however, I have been unable to find any details on this reaction, can anybody provide a
reference to this? It would be great as Iron salts presumably pose less problems due to toxicity & environmental pollution than do the lead salts.
| Quote: | Sauron said
And I still think the malonic ester route from phenylacetyl chloride is better. For one thing, you don't have to deal with Pb-compound contamination
in the P2P and further down the road. |
I would agree wholeheartedly, except for the minor caveat that the chances of the average (on the whole exceptionally paranoid) P2P cook getting hold
of chlorinating agents capable of doing the job are somewhere between slim and fuck all. In order for this route to work someone would have to come up
with a feasible route to such compounds - with the minor difficulty that the persons most likely to be using the same would be prone to topping
themselves in the process. However, given your preference for pro-active Darwinism this may appeal?
PS For those still wondering why I am trying to establish better reported routes to certain compounds, read my posts, for those wondering why I walk
so far off the beaten track - I derive no pleasure from the reiteration by rote of what is already known - looking at the literature certain areas of
chemistry which are of some interest are improving in leaps and bounds, I don't see why amateur chemistry should stay in the stone age.
[Edited on 23-5-2007 by tupence_hapeny]
We are all the sum of our experiences, and our reactions to the same
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Sauron
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If we limit this to the classical reagents SOCl2, PCL3, POCl3, PCl5 then I would concurr.
However we have slain many an electron on this forum elucidating the use of the following readily available chlorinating reagents to prepare acyl
chlorides:
benzoyl chloride
phthaloyl chloride
oxalyl chloride
cyanuric chloride
The last of which (CC, TCT) can also be used to prepare each of the other three, although phthaloyl chloride is best prepared from phthalic anhydride
and benzotrichloride.
None of those reagents is watched, nor are they considered to be CW precursors unlike the classical chlorinating reagents.
So the phenylacetyl chloride route is not quite as remote as you think.
Never heard of iron acetate being used in place of lead acetate, I would think it would require temperatures beyond what Pyrex can handle. But who
knows? I quit mucking around with P2P when John Travolta was a young star and the Shah of Iran was still on the Peacock Throne. In short, a longish
time ago.
[Edited on 24-5-2007 by Sauron]
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Organikum
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The thread is about lead dry distillation. You are distracting it for your own interests in chlorinations. Open a own thread about this and dont
destroy constructive discussions for your own interests.
(edited for civility)
[Edited on 5-24-2007 by Polverone]
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vulture
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Don't make me shut this one down.
And Orgie, if you have issues with Sauron, resolve them OUTSIDE of this board. Nobody is immune.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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MEXCHEM2006
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mix 400 gr PAA and 1,200 gr of Lead Acetate in a 2 L round bottom flask , destillation setup , in a cooking oil bath , use a calcium chloride ice
water mixture and run it thru the bulb condenser , you will first have water coming , after all the water has come out you start a partial vacuum (8"
Hg suction on a standard gauge), at approx 195°C (temperature of the oil bath ) a white liquid will distill (if your condenser isnt cold enought you
will have toxic lead fumes coming out of your condenser) , once you reach 240 °C (temperature of the oil bath) the p2p will come over , it takes like
an hour for all to come over , once it stops distilling ,, you will have in the receiving flask 2 phases (the top yellow phase is the p2p) , the yield
is in the range of 60-70 % depending on your skills.
You can clean your glassware using first water , this will disolve alot of the solid residue , then use [ ] sulfuric acid (beware of the fumes ) leave
it for an hour and then throw it away , clean again with water , doing this you would end up with very clean glassware.
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Organikum
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Thats practically identical to:
http://www.erowid.org/archive/rhodium/chemistry/p2p.paa-pb.h...
What I dont understand how you can have toxic fumes coming out of your condensor when you have hooked the setup to a vacuum?
I think thats a copycat post, the original is better.
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solo
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From what I understand, knowing MEXCHEM2006, the posted synthesis is based on the Rhodium article save the hands on notes....also even with vacuum
the exhaust of the vacuum would still have the vapors unless a trap is installed to specifically neutralize or absorb the lead fumes..........solo
It's better to die on your feet, than live on your knees....Emiliano Zapata.
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MEXCHEM2006
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If you dont cold enought your condensor a white smoke comes out of the condenser to the vacuum pump and to the atmosfer, and its not lead , its
organic lead compounds (that you have to condensate ), if you use the vacuum that the article from rhodium says you get a marvelous 20% yield .
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postart
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Has anyone attempted the Calcium acetate varriation of this distillation? Calcium acetate is easy to obtaine + it's not toxic and doesn't leave
moonrocks in your flask. I have some PAA and was thinking about a dry distillation of PAA/calcium acetate to yeild the ketone. I haven't been able to
find much lit on the calcium variation does anyone have any advise, tips, or what not. Any comments and advice appreciated!
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postart
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I am aware of this. I was looking for info more related to the distillation rather than legalities but thank you for taking time to help.
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