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Sauron
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Reliable other members with experience in this area report no success at trying to convert PCl5 to PCl3 or at obtaining PCl3 from chlorination of red
P.
Like, garage chemist. I believe him.
Anyway we are not concerned with PCl5 but with POCl3.
The reaction of PCl5 with water or alcohols produces POCl3 and HCl or RCl
If HCl on POCl3 reverses that reaction under any conditions I am unaware of it.
If that were so then
POCl3 + 2 HCl <--> PCl5 + H20
The problem being to segregate the products at the right before they can react I do not believe this is preparatively useful.
---------------
H3PO3 = P(OH)3 and PCl3 is its acid chloride.
P2O3 (P4O6) is the anhydride, produced by burning P in limited air or O2. VERY toxic. So it's a good thing we can't get P so we are not tempted to
make it!
P2O3 reacts with oxalyl chloride to produce PCl2, CO and CO2. In short, since the carbon oxides are gases, PCl3 is the only liquid product.
Can we start with H3PO3 and use excess oxalyl chloride to dehydrate the acid to P2O3 in situ? Maybe.
2 H3PO3 + 6 (COCl)2 -> 2PCl3 + 6HCl + 6 CO + 6 CO2
which is the combined form of the following two equations:
2 H3PO3 + 3 (COCl)2 -> P2O3 + 6 HCl + 3 CO + 3 CO2
P2O3 + 3 (COCl)2 -> 2 PCl3 + 3 CO + 3 CO2
Oxalyl chloride is expensive, but I don't care too much about that.
This ought to work.
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How about H3PO3 + PCl5?
This would shift the problem back to getting red P.
Let me think about this. The analogous reaction for H3PO4 is well known. Looks like H3PO3 + PCl5 would produce a mixture of PCl3 and POCl3.
H3PO3 + 3 PCl5 -> PCl3 + 3 POCl3 + 3 HCl
In the reaction of H3PO4 with PCl5 this does not arise since both the hydrolysis of the PCl5 and the chlorination of the acid produce POCl3.
Anyway oxalyl chloride is clealy better.
Yes I am well aware that H3PO3 commercially contains a little water. No that is not built into any of the above.
[Edited on 2-11-2008 by Sauron]
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not_important
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Most ferrophosphorus seems to come from China these days, and in large lots as they are targeting industrial users. I believe the usual types are 1/4
and 1/3 phosphorous, purity over a wide range depending on needs.
But unless you get lucky it appears to be mainly an industrial produce, and you don't seem to want to buy 1000 kg so it's likely not practical.
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Sauron
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No luck so far, tomorrow I will put my importer to work on it.
With the rodenticide type (P-rich) phosphides there may well be import problems even if I can source them anywhere.
And I note with chagrin that the cretin who wrote the Wiki piece on Ca3P3 stresses, from the start, purported applications to incendiary bombs. This
is alarmist, it is ancient history, no one uses Ca phosphide this way now, it's an agro-pesticide nothing more. But that's just the sort of thing that
would get Thai Customs very upset. What rubbish!
Ferrophosphorus by the way is mostly Fe2P ferrous phosphide, although that is 21% P and ferrophosphorus goes up to 27%.
It's a byproduct of WP manufacture. By far the most mass produced phosphide.
Phosphor bronze is about 1% P as Cu3P with a little tin.
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Sauron
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Pardon the double post but I would like to summarize:
Some time back I made the observation that Roger Adams' prep-1920 paper in JACS pointed out that oxalyl chloride reacts with certain inorganic acid
anhydrides (i.e., oxides) to produce the corresponding acid chlorides. The examples he demonstrated were AsCl3 from As2O3, chromyl chloride from CrO3
and one other, I forget which. My observation was that this reaction will work with P2O5 to produce POCl3.
Well now we have a cheaper way to produce POCl2 from P2O5 and NaCl.
So I turned my attention to PCl3. The requisite P2O3 is unavailable but we can buy H3PO3 (P(OH)3) and simply throw enough oxalyl chloride at it to
effectively make P2O3 in situ.
I am sure I need not point out that phosgene would act just like oxalyl chloride does.
So the problem is solved, albeit expensively. I can achieve some economy by making my own oxalyl chloride using TCT and anhydrous oxalic acid.
The phosphide route is uncertain of supply, unsure of importability, and iffy as to result.
So I am for the time being, satisfied.
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Sauron
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From this point on this thread is a continuation of discussions in the Acetic Anhydride thread on making POCl3 and/or PCl3
In particular the chemistries of H3PO3 and P2O3/P4O6
To recap:
Just as P2O5 (P4O10) is the acid anhydride of H3PO4, the familiar orthophosphoric acid, P2O3 is the anhydride of H3PO3 the less familiar phosphorous
acid sometimes called phosphonic acid.
H3PO3 exists in tautomerism between P(OH)3 and HP(=O)(OH)2
POCl3 is the acid chloride of H3PO4 and PCl3 is the acid chloride of H3PO3.
We have a number of ways to prepare POCl3 but only one for PCl3 which is unavailable to us because it requires WP.
We can obtain PBr3, H3PO3, and P2O5 without any trouble.
One prep of POCl3 from P2O5 and NaCl produced 10-25% PCl3 by wt of POCl3 formed so if we make enough POCl3 by this methos we will obtain a decent
amount of PCl3 and maybe our problem is solved.
We know that oxalyl chloride according to Roger Adams, reacts with some inorganic oxides that are anhydrides of mineral acids, to produce the acid
chlorides. Adams demonstrated this with As2O3 to obtain AsCl3 in excellent yield. We have long theorized therefore that oxalyl chloride will react
with P2O5 to give POCl3 and with P2O3 if available to yield PCl3.
Thorpe and Tutton in JCS Trans., 1890 57 545 prepared P2O3 from WP and limited O2 in CO2 and reacted it with Cl2. He obtained POCl3 and a glassy
metaphosphoryl chloride.
It turned out however that Prof.Thorpe's P2O3 contained appreciable amounts of WP which helps explain the violence of the chlorination and so perhaps
PCl3 was formed but under those conditions, may have scavenged enough O2 from the reaction vessel's atmosphere to be oxidized to POCl3.
On the other handP2O3 is a very odd compound as can be seen from its reactions with cold water and especially hot water. A review in Inorg.Chem. 5
(1966) documents the chemistry of P2O3/P4O6 which sometimes eacts very energetically and can undergoe simultaneous oxidation-reduction.
For example with hot water, P2O3 almost explosively decomposes to red P, PH3 and H3PO4. Huh? That's simultaneousreduction ( -> P and PH3) and
oxidation (to P2O5 which hydrolyzes to H3PO4 with water.
Go figure.
Therefore I am not prepared to say what P2O3 will do with oxalyl chloride. It might smoorhtly be chlorinated to PCl3 as I wish, or it might do
something unexpected.
I probably will not find out in absence of WP.
But I can get H3PO3 and try that. Again there is a large uncertainty factor.
I have some papers to read.
P2O3 can be prepared from PCl3. According to a paper in Ber. in 77 (the citation is incorrect in Merck, they got the right volume only. They have page
as 689 when it is 698 and year 1944 when in fact it is 1945 as the volume straddles both years.) Anyway PCl3 is reacted with trimethylammonium sulfite
in liquid SO2 as solvent. I love learning new reagents.
To me, the transformation PCl3 -> P2O4 is a hopeful omen, as it implies that P2O3 -> PCl3 ought to be possible. Better, maybe the available PBr3
might work instead of PCl3 our target.
I am awaiting these papers. Will post them here asap.
[Edited on 4-11-2008 by Sauron]
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Sauron
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The upshot of that review in Inorg.Chem posted in post just above is that most of the "violent" reactions of P2O3 in solid or liquid phase can be
controlled by proper technique. This includes the hydrolysis with cold water which when conducted properly gives exclusively the normal
(orthophosphorus acid) product as one would expect from an anhydride.
About the only reaction which was not amenable to mederation was that with methanol.
--------------------------
In liquid SO2 as solvent
2 PCl3 + 3 [(Me4)N]2SO2 -> P2O3 + 3 SO2 + 6 [(Me4)N]Cl
Isn't that sweet? And I see no reason why the available PBr3 should not work just as well.
If so we can get P2O3 without recourse to elemental P at all.
Scaleup may be a bit of a problem.
For joy for joy!
[Edited on 4-11-2008 by Sauron]
[Edited on 4-11-2008 by Sauron]
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Sauron
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Here is a German review article from Z.Anorg.Allgem.Chem. covering three preps of P2O3 including the one from PCl3 above. The others are from the
elements with the air diluted with N2O or N2 and run at diminished pressure so the liquid P2O3 distills off.
The prep from PCl3 in liquid SO2 works best at 80-100 mmols per 250 ml SO2 with yields up to 85% So a prep run in a liter of SO2 would yield about 15
g P2O3.
[Edited on 4-11-2008 by Sauron]
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Klute
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How do they form tetramethylammonium sulfate? Heating dimethylsulfate with excess trimethylamine? Wouldn't that form the hydrogenosulfate?
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Sauron
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Sulfite not sulfate.
I do not know ywt, I have two German papers to translate and about a dozen ACS articles and some googling results that will reveal the answer. However
TMA-sulfite appears to be a relatively populat CTH agent, reducing agent, etc. When I have the details of prep I will post.
Were I to speculate I would say that passing SO2 into a solution of tetramethylammonium quaternary salt would suffice.
Tetramethylammonium chloride is rather cheap - $35 for 250 g (Acros) so if this is starting material, no worries.
[(Me4)N+]2[SO2]-2 sorry this does not support superscript or subscript text
This is a n ionic compound (quaternary ammonium salt)
whereas dimethyl sulfite is an ester (MeO)2SO2
and Me2SO2 would be dimethylsulfone.
[Edited on 5-11-2008 by Sauron]
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Klute
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Maybe methylating trimethylamine with dimethylsulfite? Or using SO2Cl2 in a way or an other (although Cl2 might oxidize the sulfite to sulfate?)
have you got any indication for it's use in CTH? Seems quite interesting..
EDIT: apparently tetramethylammonium sulfite solution are prepared by bubbling SO2 in a solution of tetramethylammonium hydroxide... Seems pretty
easy. Drying the salt might be another story though.
I guess you could use the hydroxide with a little % of water, enough to form H2SO2 in-situ, and then remove the formed water under vacuum or by
azeotropic removal , and complete drying over P2O5 or by adding SOCl2?
US4400397
This might be usefull too:
http://www.rsc.org/publishing/journals/DT/article.asp?doi=DT...
EDIT: removed brain fart.
[Edited on 5-11-2008 by Klute]
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Sauron
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Yes there is mention in one of the ACS articles I found using their SE of CTH use of this compound. I searched all journals, all dates, using OR
boolean switchs, on title and full text keywords tetramethylammonium sulfite and with page set to 100 responses I got 25 hits. I pulled up the ones
from J Org Chem to read first (from my archive) rather than having to go through References.
--------------
An interesting article from Ber. 34 (1901) by Krafft et al. This reports that transformations are possible between oxides or chlorides (and I assume
other halides) and the elements of same group (P, As, Sb).
Thus 4 PCl3 + Sb4 -> 4 SbCl3 + P4
I already posted the Brauer prep of red P from PBr3 and Hg metal. The Krafft reactions are similar.
_________________________
I just received another paper by Wolff from Berichte in 1929, this one related to the last mentioned, but one reaction looks even sweeter for
extracting the elemental P content of PX3 halides,
4 H3PO3 + PCl3 -> 3 H3PO4 + 2 P + 3 HCl
The 2 P there is really 0.5 mol P4 = 62 g from 1 mol PX3 and 4 mols orthophosphorous acid. I have 1 Kg of the tribromide, which is a little more than
4 mols. So this requires 16 mols H3PO3 if I want to reduce it all to red P, which would be if I got the arithmetic right almost 250 g.
If and when I figure out how to take that to PCl3 it would be about 600 g. That would make me happy, especially augmented with more from the P2O5/NaCl
reaction.
Because of the uncertainty of getting from red P directly to PCl3, I might opt to wait. To be certain of PCl3 I'd have to convert the red P to white P
and that is a task neither easy nor without hazard.
Anyway this line of inquiry is so far unusually productive.
[Edited on 5-11-2008 by Sauron]
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Sauron
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The paper referred to in last post by Wolf and coworkers is attached. The reaction I highlighted, between phosphorous acid (phosphonic acid) and PCl3
was reported by Michaelis, in J.Prakt.Chem 8, 359 (1873) I am seeking the paper in References, all I know so far is thet reaction proceeds at 150 C.
The attached paper (Wolf et al) was an attempt to extend the work of Krafft to prepare P2O3 from PCl3 and H3PO3 It ended in failure. But it pointed me
at the Michaelis paper in next post, from Annalen 325 p365 (1902) which looks very useful.
[Edited on 5-11-2008 by Sauron]
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Sauron
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This paper by the famous A.Michaelis describes the reaction of H3PO3 with PCl3 to produce elemental P and H3PO4 along with HCl.
12 g H3PO3 and 5 g PCl3 are heated 12 hours at 150 C in an autoclave. The red powder obtained is washed successively with H2O, alcohol and ether,
affording 1.15 g red powder which analyzed as 93% P, balance mostly Cl.
By using 12 g PCl3 and 12 g H3PO3, the powder analyzed as 97.83% P.
(My comment: halide contamination is not an issue since I will chlorinate this anyway to PCl3 or PCl5 so the original stoichiometry is better.)
The yield is 50% of the theoretical.
Yhe significance is that while PCl3 may be hard to obtain if not impossible, PBr3 is not, I can buy it and some of you may be able to as well. The
stoichiometry ought to be same, HBr will be produced rather than HCl.
I will ferret out the rest of the details.
If yield is 50% of theory I would only get c.125 g red P out of 1 Kg PBr3 this way.
The reduction with Hg in Brauer is better, almost qiantitative.
[Edited on 6-11-2008 by Sauron]
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Sauron
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I revisited that Brauer prep and I may have spoken too soon. It also produces a highly impure red P contaminated by bromine as Hg bromides, and
although the % yield may be better, the actual amount of isolated P from a mol of PBr3 is the same as in the Michaelis prep.
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Sauron
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As of 2/09 most of my goals in this area have now been achieved, at least on paper.
I set out some years ago to find ways to prepare a variety of phosphorus compounds useful as reagents for organic synthesis which for various reasons
I cannot purchase. The chief difficulty was thst I also cannot purchase red phosphorus where I am.
I wanted to be able to prepare PCl3, PCl5, POCl3, PSCl3, and some derivatives of these such as triethyl phosphite and diethyl chlorophosphite which at
first glance is rather daynting without elemental phosphorus.
But I am happy to report that this is now all feasible and that all that remains is experimental verification of the known methods.
There are two entry points.
P2O5 (P4O10) reacts at temperature with NaCl to yield POCl3, and a little PCl3.
PBr3 is available unrestricted and can be converted to PCl3 with Hg2Cl2. PBr3 can also be converted to red P with Hg metal but that process is
inefficient and gives a product contaminated with Br2.
With these points of entry, the whole panoply opens up.
POCl3 -> PCl3 ->PCl5 POCl5 is reduced with tin to PCl3 which can be chlorinated further to PCl5 as needed.
CS2 + PCl5 -> PSCl3 + CCl4 (another valuable reagent)
Phosphite esters are easily made from PCl3 and contrary to conventional wisdom can also be made from PBr3, but with more difficulty.
So unless there are snags as yet unsuspected, this is pretty much the whole ball of wax.
[Edited on 20-2-2009 by Sauron]
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