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tom haggen
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Phosphorus Chlorides
I've been reading around as usual, and as usual certain chemicals jump out and interest me. I've been taking a liking to acetic anhydride
lately and noticed that you need phosphorus trichloride as a precursor. How exactly would someone go about obtaining such and interesting organic
solvent?
[Edited on 30-1-2005 by tom haggen]
[Edited on 30-1-2005 by tom haggen]
[Edited on 30-1-2005 by tom haggen]
N/A
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enima
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Forget obtaining the chemical, its used to make sarin gas. (reacted with methanol to make trimethylphosphate).
I'm not sure about synthesis, I'm sure someone here knows a method/proceedure.
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BromicAcid
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Usually I would classify phosphorus trichloride as a reactant as opposed to a solvent but really it's splitting hairs. It can be prepared by
readuction of phosphates with HCl at high temp I believe but that's just a preliminary thought. Of course you could chlorinate phorphorous
directly too both posing their own somewhat serious problems.
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neutrino
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Someone’s been reading Mega’s site, haven’t they? If you want acetic
anhydride, there are better methods, like the one where a pyrosulfate is refluxed with an acetate. There is a thread on this at RS.
A little OT, I hear that the various phosphorus halides have different colors.
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Mumbles
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If I were ever to make Acetyl Chloride(the precursor he has in mind) I would try using SCl2 probably. Perhaps thionyl chloride*. I've seen some
references say this reaction works, and some say that it doesn't. The sulfur compounds are so much easier to produce with the much easier
aquisition of elemental sulfur.
* Produced by the reaction of SO3 on SCl2
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garage chemist
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Because I recently got 250g of technical grade red P from a new cheap source, I will also begin to work with phosphorus halides.
About 2 years ago, I tried to chlorinate red P (with undried chlorine and very primitive apparatus) and the only thing I was producing was lots of
very nasty smoke and a sublimate of PCl5. The glass tube with the P became very hot.
I'l try this again, if I have the neccessary apparatus. Suitable apparatus is the most important thing here and the reason that I didn't
experiment with this preparation since then, even though I always had more than enough Phosphorus (bought 100g from ebay).
The correct procedure for PCl3 in Jander- Blasius calls for white P, btw.
Chlorination of red P seems to always result in PCl5, perhaps this is due to the lower reactivity and lower volatility of red P.
Maybe PCl3 can be prepared by heating the easily made PCl5 with a calculated amount of red P (maybe white P is needed for this?)?
[Edited on 31-1-2005 by garage chemist]
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garage chemist
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The classic preparation of PCl3 is the reaction of white phosphorus with chlorine under an inert atmosphere and condensing the formed PCl3 vapors.
White phosphorus is next to impossible to obtain and has to be made. WP can be produced from red Phosphorus by depolymerizing it at 600°C and
condensing the vapors. This is easily done in a bent test tube (made of borosilicate glass- NOT of soda- lime glass, because this would soften at the
needed temperatures) closed with glass wool, but only small amounts (not more than 5g a time) can be produced this way.
WP also poses handling problems due to its extreme flammability (a pea- size piece will violently self-ignite after approx. 10-20 minutes and then
splatter burning WP drops everywhere- this happened to me once) and toxicity.
I did an experiment to see if PCl3 can be readily produced from red Phosphorus.
3,1 g red P (0,1mol) were added to a 250ml three-neck rbf with gas- inlet tube nearly touching the RP, a stopper on the right side and a thermometer
adapter on the middle which was stuffed with tissue paper to allow over- pressure to escape but no circulation of air into the reaction.
A chlorine generator was charged with the necessary amounts of TCCA and HCl to generate enough chlorine to, in theory, chlorinate the red P all the
way to PCl5 (a LOT of chlorine is needed).
The chlorine was dried with a sintered-glass-bubbler washing bottle containing conc. H2SO4.
When the chlorine touched the RP, the RP instantly caught "fire" with a faintly yellow flame and the rbf fogged up completely with a white
sublimate (PCl5).
The rbf became very hot.
All the chlorine was absorbed and the RP slowly vanished (see attached picture).
No liquid was produced, only heaps of white sublimate.
Chlorinating RP seems to always yield PCl5.
After all the chlorine was added, the rbf was left to cool (closed with stoppers and the thermometer adapter).
Then a small stirring bar was added and the PCl5 sublimate on the walls was scraped off by moving a magnet over the outside of the rbf. The sublimate
was quite hard and not everything could be scraped off.
To the PCl5, 1,5g of RP were added (an excess over the theoretically needed amount to form PCl3).
It was mixed with the stirring bar and then the mixture was heated.
After a while, rapidly growing drops of liquid appeared in the solid mixture. They appeared to be boiling and the reaction continued after removing
the heat source. A puddle of liquid was soon produced and I refluxed it to dissolve the PCl5 on the walls into the liquid. Everything reacted and I
had about 10-15ml of colorless liquid (fuming in air) with a sediment of unreacted RP on the bottom. I'll have to distill the crude PCl3 and
observe its boiling point (POCl3 can be an impurity from reaction with atmospheric oxygen).
So we see that chlorination of RP exclusively produces PCl5, but PCl5 reacts rapidly and completely with RP to form the desired PCl3.
No working with WP is thus needed.
Note: I did this experiment in a fume hood. PCl3 and PCl5 are listed as being "very toxic" by the merck index. I assume that the toxicity on
inhalation is meant here, since they both rapidly hydrolyse to relatively harmless products when subjected to moisture (but phosgene does that, too).
RP is a non- watched and non- regulated material in Europe (at least in germany), it's still very difficult to get, though.
If you really can't find it anywhere where you live, you might consider ordering from www.kno3.com , they ship worldwide.
The attached picture is the reaction of RP with Cl2. Note how the RP in the near vicinity of the gas inlet tube has vanished.
The green hue on the rbf is a reflection of the green flat bowl under the rbf.
I first posted this as a new thread, but then I found this thread here, so I deleted the new thread.
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chloric1
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Oh nice pic
I read an older patent about carbon reduction of phosphates at 700 C in a stream of cyhlorine gas to obtain your halides.
Also, I have the chemistry book KINGS Chemistry book 2004 by Jared Ledgard and his proceedure states you reduce tricalcium phosphate with activated
charcoal above 1000 C for about an hour then take the calcium phosphide that results and put this in methylene chloride and use rapid stirring while
adding chlorine to the mix. The chlorinated solvent would help control the reaction a little and I wonder if anyone has heard of this methodology.
[Edited on 5/27/2005 by chloric1]
Fellow molecular manipulator
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Pyridinium
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| Quote: | Originally posted by tom haggen
I've been reading around as usual, and as usual certain chemicals jump out and interest me. |
Same here. Actually the phosphorus halides have always interested me, though I've never had occasion to work with them. It's a shame that
PCl3 happens to be used in making certain things... naturally ruining it for the rest of us who genuinely love science. 
I guess we can look back into history and blame the people who invented war gases... though sooner or later, somebody would've discovered them
anyway.
Anyhow, there's something about fuming compounds that contain phosphorus... I don't know what, but they sure are fascinating.
I think in one of the standard preparation methods for PCl3, you need some PCl3 to begin with?
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akcapr
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how exactly does acetic anhydride react with water to make acetic acid? like how many molecules of h2o does it take in or watever
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evil_lurker
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| Quote: | Originally posted by akcapr
how exactly does acetic anhydride react with water to make acetic acid? like how many molecules of h2o does it take in or watever
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Acetic anyhydride is merely acetic acid that has all the water molecules removed.
Adding small amounts of water will turn it into glacial acetic acid, keep going and you got vinegar.
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The_Davster
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CH3COOCOCH3(acetic anhydride) +H2O --> 2 CH3COOH
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I am a fish
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| Quote: | Originally posted by evil_lurker
Acetic anyhydride is merely acetic acid that has all the water molecules removed. |
Incorrect. Acetic anhydride is a dehydration product of acetic acid. In chemistry, dehydration means the removal of hydrogen and oxygen atoms in a 2
to 1 ratio (as opposed to drying, which is merely the removal of water molecules). Acetic acid that has has all the water molecules removed, is
anhydrous acetic acid. Acetic anhydride, on the other hand, is a completely different chemical.
1f `/0u (4|\\| |234d 7|-|15, `/0u |234||`/ |\\|33d 70 937 0u7 /\\/\\0|23.
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unionised
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Meanwhile, back at the topic...
Does anyone know if matches still use P2S5 and whether or not you could chlorinate that to get mixed P and S chlorides?
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garage chemist
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Matchbox strikers still contain red Phosphorus (mixed with glass powder for friction and glue).
Matchheads themselves don't contain phosphorus or P compounds.
I read somewhere that the easiest way to get the P from the strikers is to slide a large lighter flame across the striker. This softens the glue and
the P paste can be scraped off with a knife while still hot. Then it needs to be washed (don't know if the glue is water-soluble or soluble in
organic solvents- this requires experimentation).
Or just buy the red P from www.kno3.com.
It's expensive though., but much less expensive than the extraction from matchbooks.
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12AX7
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I've got about 100 strike pads saved up, I was going to try distilling it off. Not going to be pretty or very high yield though, eh?
Tim
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Jome
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According to the rhodium files RP could be dissolved in acetone and then purified by I2 and HCl.
https://www.synthetikal.com/Rhodiums_pdfs/chemistry/rpbible....
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unionised
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RP doesn't disolve in acetone, the glue does.
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garage chemist
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And the iodine converts the RP to PI3, which is the wanted material for meth production, but not for us. Don't use iodine!
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Jome
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Damn, guess I should've read more carefully before posting. ..
How would one purify the P then? Sublimation?
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Tweenk
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The standard procedure to make PCl3 is reacting chlorine gas with P, at first leting in the chlorine VERY slowly, and then, when P is covered with a
layer of liquid PCl3, letting it in faster with an inlet tube stretching out under the surface of liquid.
BTW I think this thread should be moved to inorganic chemistry
And now we add powdered sugar to the previously liquefied chlorine dioxide...
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Hellhound
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If you guys want to get RP from matchboxes you can use this method: take 5-7 matchboxes, tear off strikers ,using razorblade and trying to take along
as little paper as you can.
Then put strikers in a flask and pour 38% HCl. Amount is 300-500 ml,it doesn't matter very much at all.
Heat flask on the water bath for 10-15 min. Solution will become dirty with some trash floating in it. Continue heating and in a few minutes match
strikers will become red from one side and black from the other side,where paper was.
You must catch this moment and cautiously decantate acid. Then,wash remains with water and then with acid.After this pour strikers again with 38% HCl
and let it stay for 5min. Decantate acid,wash it with water another time and pour remains on a glass plate. You may then grind it with blade and wash
another time with acetone to free it from glue(as it was already said in previous posts).
Yield is 0.3-0.4 g of RP from 5 matchboxes.
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Hellhound
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The exact composition of matchbox strikers may vary in different countries but differences aren't great.
This is one of the recipes:
RP 30,3%
Sb2S3 41,8%
Fe2O3 12,8%
CaCO3 2,6%
ZnO 1,5%
Ground glass 3,8%
Glue 6,7%
The glue is usually a kind of bone glue.
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neutrino
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We’re trying to make things in visible amounts here. We don’t all have your patience/dexterity/lack of creativity. Go look at the Phosphorus thread.
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S.C. Wack
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Believe it or not, the subject of matchbooks has come up before, such as
https://sciencemadness.org/talk/viewthread.php?tid=2142
and you can also see there that people are fond of calling bullshit on me, I'm not sure why this is.
However, the question was P4S3 in the matchheads, and what can be done with this. This is a very good question worthy of research.
This is what Kirk-Othmer 4th ed and Ullmann's 6th ed have to say about match composition:
Attachment: match compositions.txt (9kB)
This file has been downloaded 3701 times
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