Sciencemadness Discussion Board

P4O10 and P4S10 w/Oxalyl Chloride

Sauron - 24-12-2006 at 02:14

I started this thread a while back asking what would happen upon direct chlorination of P4S10 (phosphorus pentasulfide) but never got an answer.

So I am starting it afresh and reforming the postulate a bit as now I can answer this.

P4S10 is analogous to P4O10 phosphorus pentoxide. The lattr is the anhydride of H3PO4 and so we can regard P4S10 as the anhydride of H3PSO3 thiophosphoric acid.

Upon treatment with oxalyl chloride, P4O10 reacts according to the balanced equation
P4O10 + 6 C2O2C2 = 4 POCl3 + 6 CO + 6 CO2

to produce phosphoryl oxychloride (the acid chloride of phosphoric acid) and carbon monoxide and dioxide.

That is in the lit. if you look hard enough.

By analogy

P4S10 + 6 C2O2C2 = 4 PSCl3 + 6 CO + 3 CO2 + 3 CS2
ought to produce thiophosphoryl chloride.

This is AFAIK a novel reaction; if it is in the lit. I have not found it.

Inorg.Syn. vol 4 p 71 gives two methods to prepare thiophosphoryl chloride: (1) the reaction of P4S10 with PCl5, and (2) the reaction of PCl3 with sulfur and AlCl3.

Tantalizingly there is also a reference (no.5) to reaction between CCl4 and P4S10 (!) but the publication is an old Italian one I have never encountered before, from pre-WWII,

I like my idea better as the only byproducts are carbon oxide gases.

PSCl3 is the starting material for the systemic insecticides Parathion, Malathion and Systox. In synthetic organic chemistry it like P4O10 is very useful. And it is hard to come by.

As is POCl3.

Oxalyl chloride is expensive but can be made by a variety of means we have elaborated in other threads q.v.





[Edited on 26-9-2007 by Sauron]

Sauron - 25-9-2007 at 01:01

Furthermore, it is relatively easy to desulfurize P(V) com (the P=S bond) so that the process overall goes

P4S10 -> PSCl3 -> PCl3

which would be a very handy alternative to chlorinating P.

I have never found a method to reduce POCl3 to PCl3.

If we place this chain of reactions alongside the oxalyl chloride reaction with P2O10 then all of the "denied" P halides become accessible. No one is proposing to restrict the common and inexpensive dehydrating agent P4O10 and there is no great support for restrictions on P4S10 which I have readily purchased and which is used in the match industry.

Now I go look for those desulfurization methods.

-----

YES. To desulfurize a pentavalent P thiophosphoryl compound like this you react is with a trivalent P compouns, particularly phenylphosphonousdichloride. The trivalent P wants to be pentavalent badly and grabs the S from the other. So then you have PCl3 and phenylphosphonic dichloride.

This is a wee bit circular since the usual way to make the phenylphosphonous dichloride AFAIK is a Grignard on PCl3 with phenylMgCl etc. However maybe it can be purchased, or made from different starting materials or maybe the corresponding dibromide might work.

P(=S)Cl3 + C6H5PCl2 -> PCl3 + C6H5P(=S)Cl2

See JACS 83, 2299.

Org.Syn has a prep for phenyldichlorophosphine. Not a Grignard but a Michaelis-modified Friedel-Crafts of benzene and PCl3 with AlCl3. The complex is broken up with POCl3. As a means of making a reagent to make PCl3 this obviously is circular.

But phenyldichlorophosphine IS readily available commercially, from Acros, Aldrich, and Fluka, probably others. Whether or not I can get it here remains to be seen.

[Edited on 25-9-2007 by Sauron]

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Mardec - 25-9-2007 at 13:01

P4S10 + 6 C2O2Cl2 = 4 PSCl3 + 6 CO + 6 CO2 ??!!

10 S left, 4 right
12 O lef, 18 right
..

Don't you mean something like:

P4S10 + 6 C2O2Cl2 = 4 PSCl3 + 12 CO + 6 SO2

Sorry if I am wrong about this, I was just reading this when I noticed. I can't really help you, your knowledge is way past mine :-)

And how would you make P4S10. Destilling a solid mix of red P and S in a vacuum?

panziandi - 25-9-2007 at 14:58

I think the gist of it is that the phosphorus sulphide is easily obtained as its an industrial chemical used in match production... so doesn't need to be prepared, and can be convert to the thio-acid chloride PSCl3 (- which can be desulphurised to PCl3 fairly easily). If you have ready access to red P you wouldn't need to follow this route to PCl3, but the main point is that PSCl3 is a useful reagent in itself which is very difficult to get hold of, and this reaction provides a potentially easy route to this compound... which all makes sense really. It's an interesting idea... ;)

Sauron - 25-9-2007 at 17:06

Thanks, Mardec, yes, there was a typo in the first eqn and a mistake in the second, both are now corrected and balanced.

The first reaction is based on the work of Roger Adams with oxalyl chloride and mineral acid anhydrides in JACS c.1919-1920. At that time oxalyl chloride was produced by chlorinating oxalic acid with PCl5. So clearly it would have been circular to make POCl3 this way. But he demonstrated the principle on As2O3 to make AsCl3. Since P and As are adjacent in same period, and P2O3 is the anhydride of phosphorous acid H3PO3, it is clear that (if P2O3 were available) that oxalyl chloride would give PCl3. It is just as obvious that the available P4O10, the anhydride of H3PO4, will give POCl3 its acid chloride.

With the oxyacid anhydrides of sulfur, oxalyl chloride gives SO2Cl2 with SO2, and chlorosulfonic acid with SO3. There are of course other and cheaper ways to make these.

For the relationship between P4O10 and P4S10, see Wohler's pioneering work in Ber. in which he demonstrated that P4S10 (P2S5) will replace O with S in many organic compounds and in the process become P4O10 (P2O5) !!

Thus with acetic acid P4S10 gives thioacetic acid and phosphorus pentoxide. With acetic anhydride P4S10 gives diacetyl sulfide and with diethyl ether, it gives diethyl sulfide, P4O10 being byproduct. With ethanol it gives ethyl mercaptan (ethanethiol) what stink!

You can find the example of thioacetic acid (or thiolacetic acid) in Org.Syn. if you do not read German.

P4S10 is routinely used to replace carbonyl O with carbonyl S.

P4S10 is flammable solid and toxic and readily hydrolyzes to H2S. So caution is advised. Not everyone everywhere may be able to purchase it.

@panziandi, thanks, yes, you understand that post perfectly. Note the corrections on the equations.

Sauron - 25-9-2007 at 18:45

Here is the Roger Adams paper from JACS.

He deomstrated the chlorination of inorganic acid anhydrides (oxides) to mineral acid chlorides with oxalyl chloride with two examples

As2O3 + 3 (COCl)2 -> 2 AsCl3 + 3 CO + 3 CO2

CrO3 + (COCl)2 -> CrO2Cl2 + CO + CO2

And he comments that it is probable that this reaction can be extended to other oxides of this type. (!!)

Arsenic (III) Chloride from arsenic trioxide and chromyl chloride from chromium trioxide, so the handwriting is on the wall for P2O3 and P2O5 (P4O10)

And, I argue, P4S10.

While I have balanced the equation for P4S10 and (COCl)2, I am not entirely satisfied with CS2 as a product. Other solutions for the equation might be found, such as one giving elemental S as a product, or another giving COS as a product that seem more likely to be real-world. CS2 forming at relatively low temperatures seems unlikely.

So

P4S10 + 6 (COCl)2 -> 4 P(=S)Cl3 + 6 COS + 3 CO2 + 3 C

P4S10 + 6 (COCl)2 -> 4 P(=S)Cl3 + 6 SO2 + 12 C

P4S10 + 6 (COCl)2 -> 4 P(=S)Cl3 + 6 S +12 CO

All balance but take your pick as to byproducts



[Edited on 26-9-2007 by Sauron]

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Sauron - 26-9-2007 at 01:02

The tantalizing reference in Inorganic Syntheses VI p.71 is

De Fazi,

Atti II cong. nazl. chim. pura ed appl. 1926, 1293

which sounds like National Congress of Pure & Applied Chemistry (year) 1926 p.1293 author De Fazi.

And all I know is that it claims P4S10 reacts with CCl4 to give PSCl3.

Naturally I will try to get this reference but in meantime it is worth noting that the following equation balances

P4S10 + 3 CCl4 -> 4 PSCl3 + 3 CS2

Now wouldn't that be loverly? as Eliza Doolitle used to say.

Rather economical cince we would have made the CCl4 out of CS2 to start with! we'd get it all back.

I wonder what Chemical Abstracts might have on this?

-----------------------------

To complicate matters a little further, according to Brauer, a German patent teached that PCl3 in vapor phase at 160 C reacts with S to form PSCl3. Lab scale procedure is detailed in Handbook of Inorganic Preparations. No AlCl3 needed and therefore no POCl3 required to bust up the complex after reaction as per Inorg.Syn.

To me this rather begs the original question I posted way back: what happens if you hit P4S10 with Cl2?

Well the vapor phase/molten S reaction is not very efficient and it is rather slow.

The AlCl3 catalyzed method on the other hand, as exemplified in Brauser, hydrolyzes the complex with water not POCl3 and claims a 97% yield. Clearly, this one is the best alternative, to the thus far untried oxalyl chloride method and the still amorphous CCl4/P4S10 method.

Here are the Brauser pages.



[Edited on 26-9-2007 by Sauron]

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Mardec - 26-9-2007 at 03:57

So PCl3 can be made from red P and Cl2 gas? Interesting, I have red P but I am not going to try it.. PCl3 is very toxic..


P4S10 + 3 CCl4 -> 4 PSCl3 + 3 CS2 sounds interesting, but formation of CS2.. are you sure? Would it just desolve.

P4S10 in matches hun.. I thought they where sulpher free these days.

Sauron - 26-9-2007 at 04:15

Inorg.Syn says you can make PCl3 from red P and Cl2 in presence of PCl3 to suppress formation of PCl5.

The experience of one of our members is that from red P all you get is PCl5, and that PCl3 must be made from white P (much harder to get.) So I rather hope Inorg.Syn. is right.

I do not recommend trying to get P4S10 out of matches. What is in matches is normally P2S3 admixed with many other things. I recommend buying P4S10.

If you can.

I am not completely certain about getting CS2 out of the purported rxn of CCl4 and P4S10. That equation was my own and while it balances, the by product(s) may be differed. But, I won't know what the reference says till I get my hands on it and I won't know if it works till I try to replicate it.

But, where does CCl4 come from? while you could chlorinate methane all the way, most CCl4 has always been made by chlorination of CS2. An intermediate is CSCl4 that is, CCl3SCl). A byproduct is a mix of sulfur chlorides. If you add a FeClx catalyst yopu get only CCl4.

So a reverse of this process is not unthinkable. People usually think of CCl4 as an inert solvent but it is actually highly reactive under certain conditions.

woelen - 26-9-2007 at 05:01

Is there really P4S10 in matches? I don't think so. I thought it was a lower and not hydrolysable sulfide, like P4S4.

Oxalyl chloride is not available for me, but I do have P4O10 and SOCl2. Could these be used to make POCl3? Of course, I first could make oxalyl chloride from SOCl2 and (COOH)2, but I have understood that this is an awkward reaction, which requires a lot of SOCl2 and is rather slow. I am a little hesitant of experimenting with SOCl2 if I am not knowing exactly what could happen, due to the extremely pungent and toxic nature of many compounds involved. I have to do these experiments in the open, without fume hood, and not knowing precisely what I could possibly make, I first would like to have some advice on this.

I also have NbCl5. This is a fuming yellow solid, which quickly turns white in contact with air (formation of NbOCl3, followed by formation of Nb2O5). How much does this compare to PCl5? In inorganic chemical experiments I noticed that this is violently hydrolyzed by water. NbCl5 is fairly easily reduced, e.g. to dark blue Nb(IV) compounds. I tried that with zinc as reductor.

Sauron - 26-9-2007 at 05:40

Sorry but thionyl chloride will not chlorinate oxalic acid. It just fails.

There are only two reagents I know of that will chlorinate oxalic acid. One is PCl5 and therefore, basically unavailable for most of us. The other is CC (TCT) which is available to some of us, but hard to make yourself. If you can buy it it is far cheaper than any other method to make oxalyl chloride.

I never said that anyone can get P4S10 from matches. I gather from the usual basic refs that the stuff is or was used in that industry. I agree with you that most match formulations I have read contain a lower P sulfide, Along with a lot of other stuff. Sort ing that out would be a nightmare and I have no indication that the lower P sulfide is synthetically useful for anything.

Nor is making P4S10 a viable option even is you have lots red P. See Brauer for details.

So buying it if and where you can is the only answer.

SbCl5 as a potential chlorinating agent for red P is Ozone's idea.

The point about oxalyl chloride is that its chlorinating powers are very similar to those of PCl5 and so is its dehydrating power. PCl5 will make both oxalyl chloride and TCT. TCT will make oxalyl chloride. Neither will make PCl5.

I hope this helps.

PS Ullmann's says P4S10 is used for lubricating oil additives, insecticides and flotation agents. Of these the most important are dithophosphate esters of alcohols and phenols.

The P-sulfide used in the match industry is P4S3 and then only for strike-anywhere matches. P4S3 is the only P-sulfide that can be melted without partial decomposition.

I hope that resolves the confusion.

[Edited on 26-9-2007 by Sauron]

garage chemist - 26-9-2007 at 07:18

I have done the chlorination of red P in chloroform several times, always at temperatures near the boiling point, and this always directly gives PCl5. PCl3 doesnt even seem to be an intermediate in this reaction! Even when more red P is added to the solution/suspension of PCl5 and it is refluxed, no reaction takes place. The PCl5 stays PCl5.

Only the dry reaction of PCl5 and red P gives PCl3. This, however, is not a very good method due to a significant amount of POCl3 being produced as byproduct.

I have also tried the chlorination of red P in premade PCl3, this does not work due to instant clogging of the chlorine inlet pipe by PCl5, even at the boiling point. The clogging of the inlet pipe was also a problem with the chlorination of red P in chloroform, although not as severe.

A method that I think is very promising is the use of a high-boiling solvent as the reaction medium of red P and chlorine. I am thinking of pentachloroethane, which is easy to prepare oneself by addition of chlorine to trichloroethylene, and has a reasonably high boiling point. As the dry reaction of PCl5 and red P shows, a high enough temperature will effect their reaction.
One would then suspend red P in pentachloroethane and add enough chlorine to only convert a part of the P to PCl5. Then reflux to effect reaction between P and PCl5 and distill off the PCl3.

The fact that trichloroethylene is very difficult to get here (classified as toxic and carcinogenic in the EU) has prevented me from trying this until now. I have acquired a small amount of it, but think of it as being too valuable to use it up like that.

I rather convert my red P to white P by vacuum sublimation, and react this with chlorine in the abscence of any solvent.
This makes PCl3 very nicely. I am not afraid of handling white Phos, it is infact my favorite chemical due to its spectacular reactivity.
The only limitation to this process is that conversion of red to white P can only be done in small batches due to technical and safety reasons.
Red P needs at least 600°C to sublimate with useful speed, and under vacuum even high-quality borosilicate flasks slowly deform under this heat.
Also, if the apparatus shatters, you potentially have a very big problem. Phosphorus burns are extremely painful and can poison you through absorption, with consequences like liver cirrhosis from sub-lethal amounts.
I have done the conversion in batches of not more than 5g until now. I have acquired a 30ml quartz flask which should enable me to do the conversion in batches up to 10g at a time, but have not used it yet.

White Phos also splatters should it catch fire during the followup purification (self-ignition temp is 50°C, and it catches fire even when wet) and small particles of burning P are sprayed around. When you turn off the light afterwards, you can see tiny green glowing dots everywhere... this happened to a hobby chemist I know, hed had to wash his hair with CuSO4 solution because there were glowing dots in his hair as well. Of course he wore full body and face protection, but his hair was exposed. P4 is fun.

Sauron, can you get P4S3? This is the material used in strike-anywhere matches. Chlorination should afford a crude mix of PSCl3 and PCl5, and you can distill off the PSCl3.
Does PSCl3 further react with chlorine? If yes, you can separate PCl5 from sulfur chlorides by adding chloroform. PCl5 is sparingly soluble in cold chloroform, and well soluble in hot chloroform as I have found out.

You might be able to reduce PCl5 to PCl3 with a metal, or desulfurize PSCl3 by a method you know.

Eclectic - 26-9-2007 at 07:56

Why not chlorinate the red P dry and distill off PCl3 as it is formed at the higher temperature?

Sauron - 26-9-2007 at 08:05

Thanks, g c. I buy P4S10 from Merck but the agent rapes me so I am going to switch to Acros. If either sells P4S3 I can likely get that.

Acros charges less for a Kg P4S10 than I paid for 250 g from the Merck reseller here. So even if I end up paying 2X the Acros price I will still get 2X the product for the $$

I just downloaded eight ACS articles dealing with a variety of novel (to me) reactions of P4S10 w/organic compounds, let me digest these and report back.

Antwain - 26-9-2007 at 09:03

@Sauron - when you say that P4S10 is hydrolised easily, how bad of a smell are we talking about. When I was much younger I once pulled a prank with ~25mg of iron sulfide. That was bad, bad to the point of hazmat people coming to spray probably peroxide into the air. I developed a new understanding of what ppb means. That kind of 'fun' is long behind me, but I'm wondering, if you open a bottle of this stuff anywhere but under a fume hood is it going to start churning out H2S from moisture in the air, or do you just need to keep it away from water and similar things which can hydrolise it?

Also, I can't find the damn reference, I looked for ages, but I have seen a similar reaction to the one with oxalyl chloride, and I would expect that COS rather than CS2 would be formed.

Sauron - 26-9-2007 at 09:19

P4S10 is a solid and comes in metal cans, the ones I have are all 25 g and I have 10 of them. I will open them in a dry box (glove box) well dessicated and with airlock. The dry box later gets purged into hood. The hood vents to a massive scrubber. So I doubt the neighbors will notice.

You may be right about COS. We will see.

Mardec - 26-9-2007 at 10:20

COS, dahm I even never heard of this molecule.

(ClC=O)2, I think I can get that, I have a direct contact that orders from VWR international, they have everything.. well almost everything but it costs.

And I like to make things myself. Buying precursors is something that everybody can. But making them yourself..

Like axt in hun pentryl quest, he made all the precursors, even benzene.


Anyway, why do you need PSCl3 anyway?

Eclectic - 26-9-2007 at 10:41

COS is Carbonyl Sulfide

garage chemist - 26-9-2007 at 10:55

Can one make P4S10 oneself from red P and sulfur? I'm interested in this material, even if only as a convenient source of high-purity H2S that doesnt need heating to evolve the gas (I have ZnS and it sucks, it needs to be boiled with HCl to react).
HoWi says that the reaction of red P with sulfur is vigorous, having to be done under CO2 atmosphere to avoid explosive ignition.
And Ullmann says the product is distilled? Is the reaction of stochiometric amounts red P and S even complete on its own after ignition, or will it stop at a lower sulfide?

Sauron - 26-9-2007 at 18:57

See Brauer for lab prep details. The nomenclature is odd, look for P2S5, or P4S10

I think he has it as diphosphorus pentasulfide or tetraphosphorus decasulfide. It's in the Phosphorus chapter unsurprisingly.

Quite right, @eclectic, though COS (O=C+S) has other named as well. Don't worry, no one will be breathing it. Hood, scrubber etc.

COS is commercially available (Aldrich sells it in LBs)

Here's Baruer pp 563-567 covering P4S3, P4S5, P4S7, and P2S5 (P4S10) preps. A little laborious. You take the initial crude product and seal it in a glass tube, place that in a larger diameter iron pipe packed with sand, cap that and heat the pipe in a tube furnace at 700 C for a time. So you need a tube furnace.

The P sulfides lower than P4S10 do not undergo any of the reactions with organic compounds and so are of little interest to me. I only included them because you mentioned an interest in P4S3 for chlorination.



[Edited on 27-9-2007 by Sauron]

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Sauron - 26-9-2007 at 19:42

Mardec, I don't *need* PSCl2, I have a somewhat fading need for PCl3, and I am speculating that I can desulfurize PSCl3 to PCl3.

Much of my use for PCl3 is now taken care of by PBr3.

To desulfurize a P(V) compound like PSCl3 you react it with a P(III) compound that really wants to be oxidized to P(V). The literature mentions PhPCl2 for this purpose. It garbs the S from the P atom in PSCl3 and runs like a NY chain-snatcher. Becoming PhPSCl2. I think essentially any P(III) compound will do the job, like Ph3P that I already have (that's triphenylphosphine.)

Oxalyl chloride is nasty, corrosive, irritationg, and likes to decopose to carbon monoxide. Store it in the cold, and only open it in the hood with sash down and gloves on. Always assume the bottle will be under some pressure and will vent when opened. You do not want to inhale (COCl)2 vapor nor CO and you do not want to get any splatter of oxalyl chloride on your skin or in your face. A useful tool but one that demands respect.

Sauron - 27-9-2007 at 07:39

Another reaction of P4O10 and P4S10

Phosphorus pentoxide reacts with benzene at 275-325 C (stirred autoclave, molar ratio 20:1 excess of benzene 24 hrs)

The product after hydrolysis with hot water is PhP(O)(OH)2 phenylphosphonic acid, along with orthophosphoric acid. Sadly this is not the phenylphosphinic acid we would be happer to get but it is interesting. It can be chlorinated to PhP(O)Cl2.

A similar reaction takes place with benzene (again in large excess) and P4S10, proceeding at lower temperatures and with a different workup. The reaction is not smooth for benzene itself but works well for anisole.

The JACS 76 1045 (1954) for the P4O10 reactions and the subsequent article on the reactions of P4S10 are attached.

I rolled them into a single pdf.

[Edited on 27-9-2007 by Sauron]

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Sauron - 27-9-2007 at 23:23

The literature contains an example of the use of phenyldichlorophosphine to reduce the complex Me[PCl3][AlCl4] to MePCl2. Normal hydrolysis of this complex gives MeP(O)Cl2.

If I recall correctly, the complex from PBr3 is also possible, I will have to review.

Furthermore, tributylphosphine is also effective for this reduction although yields are somewhat lower (60% vs 80+%)



[Edited on 28-9-2007 by Sauron]

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Mardec - 28-9-2007 at 08:12

Correct me if I am wrong.

Sauron needs PCl3

PBr3 is made (easely) from P + Br2

2 PBr3 + 3 Cl2 -> 2 PCl3 + 3 Br2

That Br2 can be used again to make PBr3 .. and so one.

I think Woelen once made PBr3 from Br2 and red phophorous, but I can't find the experiment on his webpage anymore.

Sauron - 28-9-2007 at 08:39

What makes you think, Mardec, that Cl2 will displace Br in PBr3?

I am all ears.

I purchase my PBr3, I don't make it. If I had red P I would try to make PCl3 but more likely end up with PCl5 - which still has its uses of course. PCl3 is NOT readily made from red P, it is readily made from white P.

One of our most competent and experienced members has been kind enough to give us the benefit of his considerable experience in trying to make PCl3 from red P under various conditions, and he says this is a tale of unmitigated woe.

I have seen nada in the literature to support a simple halogen exchange such as you propose. Wereit so, I would be delighted. Were it so then reagents like SbCl3 or (shudder) SbCl5 might do the job. But lacking any literature I am loathe to expend any of my precious PBr3 to try it on the basis of a hunch.

I am reading organophosphorus chemistry and inorganic phosphorus chemistry in the primary literature in two languages covering 127 years and doing so about 8 hrs a day.

Don't get me wrong, you might be right. F does displace Cl for example, but, even that does not happen in a clean straightforward way. For example antimony fluoride dispaces only one Cl in PCl3 or in POCl3. and that in poor yield (20%). See Saunders.

Mardec - 28-9-2007 at 09:30

Well

In the first year of my studies we had an experiment involving redox reactions.

We made Cl2 with KMnO4 and HCl and putted that chlorine in CHCl3 (testtube amounts).

Then we added too a bit of this Cl2 in CHCl3 (just to keep it from flowing away, Cl2 gas..) some NaBr Solution, the whole became red/brow.

Cl2 replaces Br because it is a stronger oxidiser then Br2. Same with Cl2 to I- or Br2 to I-

So I was kinda hoping this would work to with PBr3. PBr3 after al is notting more but with Br2 oxidized phosphorus. So wouldn't Cl2 wanna replace Br2 on the phosphorus just because of the redox potential?

Sorry if I am wrong, I was just trying to apply the things I know to the unknow. It is called experimenting after all :D

Fleaker - 28-9-2007 at 10:07

I can give this a shot as well, but I'll have to get PBr3. I think there might be a small equilibrium quantity of PCl3 produced which maybe would be enough that an efficient distillation setup might make this direct chlorination worthwhile. My experience working with Cl2 and Br2 in non aqueous systems is that the Cl and Br like to hook up with each other, often resulting in various compounds. Brauer's has a good bit (I think :P) on how things like BrCl are formed... As Sauron said, there are many competing reactions and usually you won't chlorinate something fully. It may be higher up on the electron negativity scale, but it won't necessarily displace all of your other Br atoms.

Sauron - 28-9-2007 at 10:10

Sorry, but it's just not that simple.

You were dealing with ionic NaBr, while PBr3 is covalent P-Br bonds.

Furthermore the three in PBr3 are not equivalent; you might replace one and then find that replacing the second is a LOT harder and the third even harder than that. You must appreciate that PX3 (any trivalent P halide) is an acid halide of phosphorous acid, H3PO3 and that acid exists in two tautomeric forms

P(OH)3 trivalent

HP(=O)(OH)2 pentavalent

with the latter predominating.

So a simple redox model simply does not fly.

This is what makes the lower oxyacids of P so "interesting" in the Chinese-curse sense. "May you live in interesting times!"

Look up the alcoholysis of PCl3 and PBr3. The Wiki level of understanding will tell you that PCl3 makes trialkyl esters while PBr3 makes only alkyl halides. And Wiki will show you all sorts of nice mechanistic diagrams to explain this as a sN2 reaction yada yada.

Actually what goes on is that the reaction of 3 mols of ROH with one mol PCl3 releases HCl while forming P(OR)3 and HCl is quite slow to attach the O-C bond. In the case of PBr3 however, HBr is much better at the same job so you will get some R-Br and normally at best dialkyl hydrogen phosphite

H-P(O)(OR)2

That pesky tautomerism at work again!

If you allow the process to continue (but it gets slower at each consecutive stage) you will end up with 3 RBr and phosphorous acid and that is why PBr3, or red P and Br2, are a method for making alkyl halides. The red P/Br2 makes PBr3 in situ.

HOWEVER if you run this same reaction in the cold and employ three mols of a tertiary amine to trap the HBr you CAN make triesters of phosphorus from PBr3. No matter what crap Wiki puts out to the contrary.

With PI3 or red P/I2, same story only even worse. But even here under the right conditions trialkyl esters can be made, it is just more difficult. (And absurd economically.)

Note that the dialkyl hydrogen phoshite is pentavalent. You can easily halogenate that -P-H bond and make a chlorophosphite diester. You can then react that with alcohol and a tertiary amine and what do you have? a trialkyl PHOSPHATE not a phosphite at all. Just as if you have started with H3PO4 or POCl3 or P2O5. Got a headache yet? Eyes glazed over?

That last method is actually used to prepare mixed phosphate esters P9O)(OR)2(OR1) etc.

I wish it were so easy to replace Br with Cl on P(III) as you suggest.

Mardec - 28-9-2007 at 10:15

Yes of course, how foolish of me to presume all PBr3 would become PCl3 :-).

Btw PBr3 is collourless liquid right? So make some Cl2 and put it in some CHCl3, add some PBr3 and if it becomes red/brown we know..

Btw Sauron if you need red P, I know a webstore that sells it in 0,5 kg quantities.

EDIT,

I now read saurons post to... Yes, I shouldn't confuse anorganic with P chemistry.. :-)

I Get a good Idea of what you say, but it is still difficult to comprehend.. I am all new to P chemixtry.

So a triester of phophorus woud be like : (R1O)(R2O)(R3O)P right? But if it goes wrong you get crap like this : (R1O)(R2O)(R3O)P(=O) right?


And yeah, wikipedia is a nice fictional site with some real life elements.


[Edited on 28-9-2007 by Mardec]

Sauron - 28-9-2007 at 10:45

Well normally you make a triester with all three R the same, and if all goes well and you use tertiary amine and you stir well so no hydrogen halide builds uplocally...you don't get any contamination with dialkyl hydrogen phosphite. Which is undesirable because sometimes this is very hard to remove, as in the case of the ethyl esters.

My point was that normally once P(III) goes to P(V) it is bloody hard to reverse that.

Because P(III) WANTS to be P(V) or to put it in chemical terms, it is favored, kinetically, thermodynamically or both.

I could try your idea and might at some point, but I am hoarding my 1 Kg PBr3 (which not very much in molar terms not in volume as it is bloody dense) while continuing the paper chase.

I would happily buy from that website if I thought there was a chance in hell of getting it in through Thai Customs. Red P requires a special import license from the Defense Ministry, Office of the Permanent Secretary, hard to get. As you might imagine I would not care to have a package addressed to me or mine, confiscated, quite apart from the loss of $$ this could have repercussions. So alas...I will stick to what I am allowed to buy.

But thanks for the tip.

Mardec - 28-9-2007 at 10:54

Oh yeah live in Thailand. Well, then I don't think I can help you. You could try to look for a factory that makes novelty fireworks. And try to buy some red P from them.

But it seems like you manage :-).

And something I noticed. Red P with Br2, does that give PBr5 of PBr3?

Edit, PBr3 of course, my mind was sleeping..

[Edited on 28-9-2007 by Mardec]

Sauron - 28-9-2007 at 11:06

RedP with Br5 can give either PBr3 or PBr5 depending on proportions. Normally you would make these in an inert medium (red P does not dissolve in anything I can think of.) See Brauser and IS for details.

Sauron - 29-9-2007 at 01:45

Here's a relatively clear-cut reaction of P4S10 with an ortho-ester, specifically triethyl orthoformate

Heating the two gives a 92.5% yield of triethyl dithiophosphate

P(=S)(OEt)2(SEt) or P(=S)(SEt)2(Oet) - the authors were not certain which.

I would not really care as I would want to cleave the ester to PSCl3 with Cl2 and then continue the chlorination. According to Gmelin, 2 PSCl3 + Cl2 -> 2 PCl3 + S2Cl2, isn't that nice? I found this reference in a Knotz patent, US 2765561 p.2 end of example 6:

Gmelin Kraut, Handbuch der Anorganischen Chemie I, 2, Seite 192, 7.Auflage (1909)

This could be a solution for those who can't buy or make oxalyl chloride, but want to start with P4S10 to get to PSCl3 and PCl3.

The ethyl orthoformate is not hard to make. Also can be bought. Here is the Org.Syn prep from abs ethanol, chloroform and sodium metal. It is also possible to employ commercial or preformed sodium ethoxide (dry or in solution) or ethanolic NaOH - see references at end of the monograph.

Procedure:

146 g triethyl orthoformate and 61 g P4O10 are heated in a 500 ml RB flask equipped for vacuum distillation and fitted with a thermometer at the still head, the temperature being raised to 95 C over ten minutes, At this point an exothermic reaction set in and heating was stopped. In 15 minutes the reaction abated and heating was resumed. The temperature was raised to 150 C over 30 minutes; during this time 56.5 g of ethyl formate and ethyl thionoformate distilled over at 760 mm and were condensed. The pressure was then reduced to 10mm and a further 12,3 g of ethyl formate and ethyl thioformate were condensed in the dry ice-cooled cold trap, and 5.5 g of unchanged ethyl orthoformate distilled at 40-42 C.

The pressure was then reduced to 0.65 mm and 109.2 g of crude triethyl dithiophosphate distilled between 66 and 74 C(92.5%). This product was redistilled and 94 g of pure triethyl dithiophosphate boiling sharply at 115-115.5 C/10mm. Density and refractive index are given in the text.



[Edited on 29-9-2007 by Sauron]

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Mardec - 29-9-2007 at 02:09

2 PSCl3 + Cl2 -> 2 PCl3 + S2Cl2

Sounds nice, but to obvious.

But wouldn't PCl3 react with the Cl2 gas too?

PCl3 + Cl3 -> PCl5
or
PSCl3 + Cl2 -> PCl5 + S

So special conditions should be follow to avoid these reaction I guess.

-Snip-

EDIT: Stupid idea, but would PCl5 + (2)S -> PCl3 + S(2)Cl2 work?!

[Edited on 29-9-2007 by Mardec]

[Edited on 29-9-2007 by Mardec]

Sauron - 29-9-2007 at 03:06

Complain to Gmelin not to me.

Gmelin is the inorganic Bible (even more than Mellor.)

It is the inorganic equivalent of Beilstein.

So, I would suppose that Cl2 will cleave the S faster than it might add to P. If you continue chlorination beyond the amount needed, as determined by mass gain, then you would maybe start to convert some PCl3 to PCl5 - unless the S2Cl2 absorbed it first.

(Thanks for the edit.)

SCl2 is not stable. S2Cl2 is stable. If you overchlorinate S2Cl2, any SCl2 you make will slowly disproportionate to S2Cl2 and Cl2. Once again see Brauer.

As to the mix of PCl3 and S2Cl2, along maybe with some unreacted PSCl3 and some overchlorinated PSCl3 now PCl5, and SCl2, trick will be to examine the bp's and see how tricky the fractionation might get.

[Edited on 29-9-2007 by Sauron]

Mardec - 29-9-2007 at 03:23

Quote:
Originally posted by Sauron
Complain to Gmelin not to me.

Gmelin is the inorganic Bible (even more than Mellor.)

It is the inorganic equivalent of Beilstein.
[Edited on 29-9-2007 by Sauron]


I was not complaining ;-)

And I didn't know Gmelin, so I didn't know it was such a good book. I am looking to download it right now.

And I deleted the mustard joke..

I am going to look for my first year books, I just remembered there was a page about PCl3 in that.

Sauron - 29-9-2007 at 03:51

Not to worry.

Gmelin is not a book but a massive mult-shelf collection of books, so good luck on downloading. Also, it is entirely in German. (Unlike Mellor.)

Like Beilstein, Gmelin is usually to be found only in libraries. Although about the first half of the Beilstein Haupwerk is available in pdf. That covers all the alicyclic and single ring hydrocarbon lit. through 1910. The first supplement (likewise, about 30 volumes) goes to 1920, the 2nd supplement to 1930. The 3rd and fourth supplements (combined) to 1959 and the fifth supplement, only one in both German and English, to 1979.

Plus the huge indexes, particularly the centennial index.

But it is worth it to try to buy these up on used market even though it will run a couple thousand at least.

JohnWW - 29-9-2007 at 05:43

Has Gmelin been scanned and uploaded anywhere? It certainly should be, especially as nearly all of it is now out of copyright.

Mardec - 29-9-2007 at 07:28

German is not such a big problem, I am a native dutch speaker. Dutch and Deutsch are familie.

Still though I prefer english.

After Christmas I will be working (stage) in a chemical research and devellopment facility for a huge international. They have a huge chemical library (Chemicals and books). I am looking forward to it!!
So maybe I will have acces to gmelin there :-).

[Edited on 29-9-2007 by Mardec]

Sauron - 29-9-2007 at 14:15

The reaction of P4O10 wurh benzene under autogenous pressure in an autoclave (275 C, 24 hrs) is interesting and when done under the right conditions quite high yielding.

However it requires a massive molar excess of benzene to P4O10, and since the working capacity of the autoclave is 2/3 nominal capacity, and especially since benzene expands in volume threefold at the temperature involved, which is near its critical temperature, these factors conspire to demand a rather large capacity autoclave for a reaction that will produce a relatively small amount of product.

I have a 1 liter autoclave and the most I could get out of a batch I could run in that is 5-10 g phenylphosphonic acid.

Autoclaves being expensive, unless you have a big one on hand, this looks like a non-starter.

Too bad, because otherwise it looks like fun.

My target anyway is phenylphospnous dichloride. To get there from the phenylphosphonic acid is possible but extra work.

PhP(O)(OH)2 -> PhP(O)Cl2 by means of a large excess (6 fold) PCl5 in POCl3. The byproduct is POCl3 but as PCl5 is scarce, the alternative SOCl2 suggests itself even though the reaction is described as sluggish and lower yielding.

I would try oxalyl chloride instead of SOCl2.

So I just pulled up yet another Chem.Rev. article, this time on the phosphonic acids instead of the phosphonous acids, and we will see what we will see.



[Edited on 1-10-2007 by Sauron]

Sauron - 30-9-2007 at 19:40

Traditionally the routes into the R-phosphonic acids

R-P(O)(OH)2

have been few. In the late 19th century Michaelis modified the Friedel-Crafts alkylation reaction to condense alkyl halides with PCl3 (or PBr3) with the help of AlCl3.

Grignard and co workers however found that the reaction of alkyl and aryl magnesium halides to PCl3 gives exclusively tertiary phosphines. It was not until the 1950s that methods were developed that allow the use of Grignard and lithium reagents to prepare RP(O)(OH)2 and R2P(O)OH.

Generally we would not regard these techniques as familiar protecting hroup strategies.

Classical diazonium salts have failed to react with phosphorus halides, but again in the 50s, it was found that diazonium fluoborates and fluosilicates react in organic solvents with PCl3 using copper chloride as catalyst. This is an extension or special case of the Bart reaction. Yields are no better than fair but the reaction has been widely used because is has more scope than the more usual techniques and many phosphonic acids and derivatives have been prepared this way that have not been easy, or even possible, by other means.

The diazonium complexes can be worked up as either phsphonic acids or phosphonous dichlorides.

Sauron - 2-10-2007 at 00:52

Back to P4S10 electrophilic substitution reaction with anisole.

It seems that the 24 hr reaction in an autoclave is now passe. Org.Syn. has an 82% yield prep of same compound, now known as Lawesson's Reagent, done in glass under reflux, 10:1 excess of anisole, neat.

Attached.

Product is a useful and stable thiating reagent.

[Edited on 2-10-2007 by Sauron]

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Sauron - 2-10-2007 at 19:25

Some basics

Hydrolysis of P4S10

This is instructive because it is the simplest case of the thiation effect of this reagent.

Quite in accordance with my contention that P4S10 ought to be regarded as the anhydride of the real but unstable thiophosphoric acid, phosphorus pentasulfide reacts with water according to the equation

P4S10 + 16 H2O -> 4 H3PO4 + 10 H2S

In effect P4O10 thated the water.

If thiophosphoric acid were stable then

P4S10 + 12 H2O -> 4 H3PSO3 + 6 H2S

but it isn't, so an additional four mols water are required

4 H3PSO3 + 4 H2O -> 4 H3PO4 + 4 H2S

If you combine these equations you get the overall reaction.

Kekule described the hydrolysis and the alcoholysis of P4O10 in his classic paper, attached.

P4S10 + 10 EtOH -> 10 EtSH + P4O10

But in fact the interaction of P4S10 and ethanol gives rather a mess, principal products being triethyl O.O,S-thiophosphate and triethyl O,S,S-thiophosphate. So P4S10 is behaving in this instance very much like an anhydride of thiophosphoric acid.

[Edited on 3-10-2007 by Sauron]

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Sauron - 3-10-2007 at 02:04

As the attached paper demonstrates, the crude neutral fraction of the reaction product of alcoholysis of P4S10 with ethanol is a complex mixture.

However a 50% yield of P(S)(OEt)2Cl can be isolated in pure form after chlorination with a single equivalent of Cl2 in MeCl2 (DCM).

My conclusion is that further stepwise chlorination would likely yield

P(S)(OEt)Cl2, then PSCl3, and if Gmelin got it right, exhaustive chlorination would proceed to PCl3 + S2Cl2.

This may be worth a try. I will have a closer look at this paper and its antecedents.

Well the yields suck (16%) so the way to go with P4S10 is definitely ethyl orthoformate not alcohol.

Ethyl orthoformate reacts in minutes not hours or days, gives a 90+% yield of same product, and is both readily purchasable and readily preparable if you can get Na and CHCl3. Or even just NaOH and EtOH if you can wait a few days for them to react.

[Edited on 4-10-2007 by Sauron]

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