Phosgene a substitute for PCl3 in CH3COCl production?

[FadeToBlackened]

After reading that thionyl chloride can also be used for this reaction, I started looking around trying to find a synth for it. I had no luck; all I found were uses of it. I did, however, just find www.twinlakechemical.com, a supposed company that supposedly sells acyl chlorides and some of their precursors. They claim to also use phosgene. I'm not really knowledgable on this though, maybe someone else could think about it?

I also found www.chemicalland21.com, they have little bits of insight about a various many chemicals and often a little description of how they are made. Just thought I'd add that.

So aside from the inherent danger of using phosgene for halogenating acids, (not that PCl3 would be friendly..), would it be possible?

Edit: The more I search the more I do see COCl2 referred to for this.

[Microtek]

Seeing that SOCl2 is used in many chlorination reactions, I looked into production as well. I found that the reaction of SO2 with Cl2 produces it along with some byproducts.
While both SO2 and Cl2 are nasty, they could be absorbed or destroyed without too much trouble. The question is how difficult it would be to separate the SOCl2 from the byproduct.

[FadeToBlackened]

from http://www.xdhg.com.cn/article/2002/abs/e-abs-2002-03.html:

Abstract: Applications of thionyl chloride in pharmaceutical and pesticide sectors and application developments in organic synthesis reaction and ring formation reaction are introduced. Synthesis methods of thionyl chloride such as HSO3Cl method, SO2 method, SO3 method, co-production method and enterprises adopting above methods are evaluated. The domestic production, demand, import and export of thionyl chloride are analyzed. It is suggested that backward HSO3Cl method should be eliminated and new plants should adopt advanced technologies. Factors such as feedstock source and scale effect should be considered when new plants are being built.


HSO3Cl, chlorosulfonic acid.. possibly made from readily available sulfamic (amidosulfonic) acid?

[Al Koholic]

By passing Cl2 gas into molten sulfur at 295 degrees centigrade one can obtain S2Cl2: Cl-S-S-Cl. This can be used in a synthesis of CH3COCl. I forget the exact details of either synthesis...I believe I may have seen it on rhodium. The appeal of this method of acyl chloride production is that all the necessary chemicals are easily obtainable. A simple chlorine generator, some pure sulfur powder, and the appropriate equipment is all that is required. I am thinking about adding the sulfur to a 500 ml two neck round bottom boiling flask. The Cl gas will be administered through the side neck via a length of bent glass tubing and a stopper. I haven't got the synth in front of me but I believe it is fairly straightforward. Just had a look at Merck...you can find a synth in- Feher Handbook of Preparative Inorganic Chemistry vol. 1, G. Brauer, Ed. (Academic Press, New York, 2nd ed., 1963) pp 371-372. Hydrolysis: H. L. Olin, J. Am. Chem. Soc. 48, 167 (1926). Merck only mentions molten sulfur so maybe my memory of 295 centigrade is incorrect. The product has a boiling point of 138 C so it is easily purified by fractional distillation. It mustn't contact water though as nasties will form.

Al

[FadeToBlackened]

Good to see someone but myself replied to this!

I believe megalomania has a synth for CH3COCl using PCl3, which says SOCl2 may also be used (S2Cl2 also?). I don't see how it would make much of a difference depending on which chlorinator you used. As I was thinking this, Nitrogen halides (being discussed a bit now) and aluminum chloride also crossed my mind.

[FlaAlchemist]

Can PCl3 be made by any other methods than reacting red or yellow phousphous with Cl2?

[nbk2000]

Passing chlorine through activated charcoal saturated with metaphosphoric acid produces PCl3.

[vulture]

How about making PCl3 from PH3?

PH3 gas (itself very poisonous) is made by reacting calciumphosphide with water:

Ca3P2 + 6H2O ---> 2PH3 + 3Ca(OH)2

Calciumphosphide can be bought as rodent poison or made by reducing Ca3PO4 with aluminium, a reaction commonly used for rodenticide smoke bombs.

2PH3 + 6Cl2 ---> 2PCl3 + 6HCl

Problems:

1) Is this reaction feasible?
2) PH3 is extremely poisonous and autoignites on contact with air.

One could also burn the PH3, collect the formed P2O5 and make POCl3 with that...

[Polverone]

One could also burn the PH3, collect the formed P2O5 and make POCl3 with that...
The combustion of PH3 is also going to produce H2O, and we all know how much P2O5 loves water.

[Al Koholic]

Yeah. Phosgene would be an excelent chlorination agent. I actually found a method of making acetyl chloride with phosgene before...can't remember what I did with it though, could find it again if theres any interest! I'll keep and eye on this thread...

Phosgene itself is made by simply running a Cl2 stream into a CO stream. The gases mix and form phosgene just like that. In fact, in old days chemists used to use equal flowing streams of these gases instead of having phosgene tanks lying around. I've never tried this but supposedly it works. You could just cool the gas stream down to 8C and condense the phosgene. If you did all this outside now you'd have no problem hehehe (NE US).

Anyway, I believe that the SO2 + Cl2 also makes appreciable quantities of SO2Cl2, another good chlorinating agent. Ahhhhh the quest for the elusive acid chloride....

[Sarevok]

PCl3 can be made by chlorinating ferrous phosphide with anhydrous chlorine at 200-486°C (less than 486°C to avoid vaporizing the product). The product is mixed with non-chlorinated ferrous phosphide, heated to 270°C and then to 300-400°C with the evolution of gaseous PCl3. 40 parts by weight chlorinated ferrous phosphide mixed with 18 parts by weight ferrous phosphide should work well.

2Fe2P + 11Cl2 ---> 2(FeCl3)2·PCl5

7(FeCl3)2·PCl5 + (4+n)Fe2P ---> 11PCl3 + 22FeCl2 + nFe2P

n equals a number greater than 0.

Both reactions are exothermic so one should not have problems to maintain the temperatures between the required temperature range. The chlorinated ferrous phosphide should be immediatly reacted with non-chlorinated ferrous phosphide and then immediatly distilled (if one is going to store it, it must be stored at its liquid state: 100-486°C).

Ferrous phosphide is stable, its only hazardous if you eat it or inhale its dust, so I think a chemical supply store would seel it without asking questions. The main problem would be generating and drying the chlorine:

Posted by nbk2000
Chlorine is made by dripping hydrochloric acid onto calcium hypochlorite (HTH pool shock, $50 for 40 pounds). Drying is done by passing through sulphuric acid or magnesium sulphate, though the acid is preferred.
Burning PH3 to make P205 to make POCl3 seems unlikely (read Polverone's post). POCl3 can be made by reacting calcium (ortho or meta)phosphate with anhydrous chlorine in the presence of carbon at 800°C.

Ca3(PO4)2 + 6C +6Cl2 ---> 2POCl3 + 3CaCl2 + 6CO (with the orthophosphate)

Ca(PO3)2 + 4C + 4Cl2 ---> 2POCl3 + CaCl2 + 4CO (with the metaphosphate)

PCl3 would be less hazardous to use than phosgene... if one really wants to use phosgene, The War Gases shows various ways about how to make it, how to detect it, how to decompose it, etc.

P.S.: Is my english getting any better? I hope it is... I've always learned it on my own; now I'm studying this Grammar, Punctuation, and Spelling (http://owl.english.purdue.edu/handouts/grammar/index.html) website. Sorry if this is a silly question.

[kingspaz]

Sarevok, yes, your english is getting much better :)

[vulture]

The combustion of PH3 is also going to produce H2O, and we all know how much P2O5 loves water.

Doh! What was I thinking! Atleast you'll have reasonably pure H3PO4 which isn't such a bad precursor after all.

Would the method to form PCl3 from PH3 work? Or will it form PCl5?

[Sarevok]

I don't know if it would work, but if it doesn't work, sparks convert phosphine to hydrogen and red phosphorus (according to Modern Inorganic Chemistry, page 226). This phosphorus could be used to make PCl3 or whatever.

Here is what I found on google (http://www.c-f-c.com/gaslink/pure/phosphine.htm):
Phosphine begins to decompose into its elements at about 375°C. It reacts spontaneously with chlorine.
Perhaps the reaction is possible, after all. If it makes PCl5 instead of PCl3, there is no problem: PCl5 dissociates (probably to chlorine and PCl3) at 600°K (something like 320°C, I think), according to the same book I mentioned above, page 251.

[FlaAlchemist]

Originally posted by nbk2000
Passing chlorine through activated charcoal saturated with metaphosphoric acid produces PCl3.



Would this work if Bromine instead of chlorine?:cool:

[megalomania]

Do you have any details on the process of passing Cl through metaphosphoric acid nbk? That sounds like a very promising route if the yields are good.

[Sarevok]

This process is described on US Patent #2712494, but it does produce POCl3, not PCl3.

I think that it would work with any halogen (perhaps not very well with iodine).

[nbk2000]

My bad. :o

It's the ferro-phosphate process that produces PCl3. The metaphosporic/carbon process produces the phosphoryl oxychloride needed for tabun.

[FlaAlchemist]

Originally posted by nbk2000
My bad. :o

It's the ferro-phosphate process that produces PCl3. The metaphosporic/carbon process produces the phosphoryl oxychloride needed for tabun.


Do you mean Ferro Phosphide or Ferro Phosphate Process :confused:

Very interesting info :cool: