madscientist
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COCl2 from CCl4
Here's a rather interesting reaction that I stumbled upon.
CCl4 + H2O --(FeCl3)--> COCl2 + 2HCl
If I remember correctly, that reaction occurs readily at warm temperatures.
I weep at the sight of flaming acetic anhydride.
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Rhadon
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Phosgene is also produced in a side-reaction in the so-called Berger mixture which is used for making black smoke. It consists basically of
CCl4 (or a similar chlorinated hydrocarbon, such as tetrachloro ethylene), Zn and some additives such as Zn and MgO. I think that the latter are only
used to lower the burning speed, thereby the temperature and thereby the amount of phosgene that is evolved. So I suppose that you could just as well
leave them away or even better subsitute them with FeCl3
The only drawback of the Berger mixture is its high ignition temperature.
The following is just what I remember, and I'm not completely sure about it. There was a website that offered interesting information (try this; the website offers documents in English and German language), but it is down right now for
some reason 
In WWI, the mixture was pressed into cans and ignited in several steps, the last being KMnO4. They didn't use it because of the
COCl2, though, but because of the high density of the black smoke.
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Polverone
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other ways?
I know that chloroform degrades spontaneously over time to form COCl2. Does anyone know of a controlled way of converting CHCl3 -> COCl2 on demand? I
wonder if oxidation with sulfuric acid would work. Carbon tetrachloride would be difficult for me to obtain, but I have plenty of chloroform on hand.
I suspect that I'll need a dehydrating agent anyway, to keep any water formed away from the COCl2, so maybe conc. H2SO4 is my best bet.
Alternately, does anybody know of a labscale process for converting CHCl3 -> CCl4?
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Rhadon
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correcting myself
| Quote: | | In WWI, the mixture was pressed into cans and ignited in several steps, the last being KMnO4. |
should be:
In WWI, the mixture was pressed into cans and ignited in several steps, the last being KMnO4 / Fe.
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Rhadon
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Polverone: Uncle Fester states that you can make phosgene by reacting sulfuric acid containing free SO3 with
CCl4 according to SO3 + CCl4 --> COCl2 + 2HSO3Cl.
I don't dare to suppose if this process will also work for CHCl3, because there are persons on this forum who can determine that much
better than me 
Note: I will once again have no access to the internet for some time and therefore not be able to post replies.
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Rhadon
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Finally I'm back to internet In the meantime, I was able to validate that
phosgene may be prepared from sulfur trioxide and carbon tetrachloride. I found the information in Mario Sartori's "The War Gases Chemistry and
Analysis". Sartori does also mention another interesting method:
| Quote: |
In the laboratory, phosgene may be easily prepared be treating chloroform with chromic acid mixture:
2 CHCl3 + 3 O --> 2 COCl2 + H2O + Cl2
By this method the product is impure with chlorine and chloroform (5% about).
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BromicAcid
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I've recently been looking into organic carbonates such as methyl carbonate and ethylene carbonate. The manufacture of such compounds requires
the use of phosgene.
So I was just wondering if any of the newer members since this thread was last accessed almost two years ago know of any other methods to produce this
chemical. I am planning on a big batch of chloroform to try and convert, and waiting till the temp outside drops below 0C but until then I will
simply plot and wait.
I have some chlorinated organics like hexachloroethane and tetrachloroethylene and such, possibly stoichiometric oxidizing mixtures involving them
could be used to yeild the desired phosgene.
Edit: But if using the chromic acid oxidation procedure, how do you overcome the reactivity of phosgene with water? A website I found says it has a
half like of .026 seconds in water so how could I use an aqueous soluiton to react with the chloroform when it will almost instantly react with the
aqueous phase. I did a quick and dirty reaction to see if anything would happen, 5 ml CHCl3, 3 ml H2O, 1 g K2Cr2O7, 1 ml HCl, the chloroform layre
immediately shrunk upon shaking and appeared to bubble some (but it could have been just the emulsion that formed). The test tube heated up slightly.
Edit #2: Now that I think about it, I remember something from when I was trying to find a procedure for making carbon tetrachloride. That heating
tetrachloroethene with copper metal and water yeilds trichloroacetic acid and phosgene and carbon tetrachloride. Hummmm.....
[Edited on 11/12/2004 by BromicAcid]
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Polverone
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What about using CrO3 in glacial acetic acid, conc. H2SO4 + dichromate, or some other non-aqueous oxidizing combination? You seem to like apparatus
okay... what about combining Cl2 and CO like it is/was done industrially?
PGP Key and corresponding e-mail address
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chloric1
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Combination
simple combination synthesis will suffice but you will need activated charcoal and possibly a UV light.
[Edited on 11/13/2004 by chloric1]
Fellow molecular manipulator
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S.C. Wack
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Everything I've seen on the hydrolysis by water suggests that it is slow, especially cold. If the CrO3/COCl2 is made in situ with
dichromate and (a large excess of?) hot conc. H2SO4 as Polverone suggested, this should go well.
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BromicAcid
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I do have an affinity for apparatuses Polverone, however I've come to find out that the more effort I put into a project the more doomed it is to
fail for some reason. So I'm trying to avoid anything complicated on this one.
Considering the ease of conversion from simple chlorinated hydrocarbon to something partially oxidized, i.e., water can do it over time and it will do
it on its own over time, maybe concentrated H2SO4 might be able to pull it off on it's own, possibly with a tiny amount of copper added. At
least it is a somewhat easily condensable liquid and able to be blocked by most gas masks. It is pretty toxic though. Never found a use for phosgene
till now.
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JohnWW
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Who are you going to gas with such a large amount of the stuff, BromicAcid? The insurgents in Fallujah? Phosgene (COCl2) is a poison war gas, much
used by the Germans in WW1 on the western front, along with mustard gas. I once knew a New Zealand WW1 veteran who was badly gassed on the Somme in
France in 1916 by the stuff, having a hacking cough thereafter as the result, and who died in 1970 aged 76 of spine cancer which may have been caused
by it.
BTW Besides methyl or ethyl or vinyl or phenyl carbonates, obtained by reaction of COCl2 with the corresponding alcohols or phenols in the presence of
pyridine, polymeric carbonates sold commercially as "polycarbonate" unbreakable glass substitutes are made in the same way, except that the
simple alcohols are replaced with diols and diphenols with the -OH groups on opposite ends of the molecules. The pyridine is converted to the
hydrochloride. One of the most important, "Lexan", is made using "bisphenol A" which is 4,4'-dihydroxyphenyl-dimethylmethane.
The presence of the para-substituted phenyl groups gives it its rigidity and hardness.
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kazaa81
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chloroform...
Hallo to all,
as one who've long searched for buy CCl4, because it isn't so common, I would suggest that if one need to make COCl2 and can get CCL4,
probably is better to decompose chloroform (CHCl3) to make it...
Thanks at all! 
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BromicAcid
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Kazaa81, that's exactly what we've been talking about, despite the subject of this thread we have been a bit off subject for a while
discussing the preparation of carbonyl chloride from trichloromethane instead of from tetrachloromethane.
JohnWW, yes, phosgene is very toxic, that is why I intend to wait for much colder weather to try anything, do the preparations in a closed system, and
run exit gasses though hot water to decompose them quite readily. I also intend to wear a gas mask although the cold temperatures and wash should
save me from any lingering toxic effects that I might experience without it. Interesting note on lexan though, I was unaware that it was a
polycarbonate.
Chloric1, I don't think UV light is necessary, from what I've read it occurs over activated charcoal at moderate temperature, although I
could be wrong, but I don't want to go the combination of Cl2 and CO method, there might be some additional danger involved over a simple aqueous
oxidation.
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chemoleo
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Alternatively, you could deactivate it with NaOH, or possibly even NH3? The latter you might want to use to flush your glassware with (i.e. the gas),
all it should produce would be urea and HCl.
Apart from reacting it with alcohols and phenols what other lovelies could one do with it?
One I could think of is to react phosgene directly with ethylenediamine... supposedly this might form ethylene urea, which has plenty of uses in the
energetic mats field (EDNA).
How about bubbling this into glycerol, or glycol?
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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BromicAcid
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Possibly just run tetrachloroethylene and dry air though a heated tube containing activated charcoal.
Cl2CCCl2 + O2 ---> 2COCl2
There is really no flammability concern considering phosgene and tetrachloroethylene are nonflammable so just achieving the proper temperature is the
achievement to shoot for. The difference in boiling points between the two should allow for easy separation once the condensed product is obtained.
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Eclectic
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Ethyl Carbonate
Bromic, If you do a patent search for ethyl carbonate and urea, there is a patent for production of carbonates using urea dissolved in alcohol under
pressure and heat. It could possibly be done in an empty CO2 tank, distilling the ammonia into another.
(Danger, Danger, Will Robinson!)
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BromicAcid
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1) Eclectic, I did the search and actually came up with a number of patents just as you said, although a number of them used some exotic catalysts,
the most tame catalyst that I saw was an organo-tin catalyst, they all involved pressures along with a constant stream of nitrogen gas to evacuate
formed ammonia, but they may prove useful some day, patent 5,565,603 is probably the best patent I found, very interesting.
2) On phosgene from chloroform;
| Quote: | Chloroform is oxidized by sulfuric acid and potassium dichromate as indicated by this reaction.
(a) H2SO4 + K2CrO4 ---> K2SO4 + H2O +CrO3
(b) 4CrO3 ---> 2Cr2O3 + 3O2
(c) 2CHCl3 + CrO3 + O2 ---> COCl2 + CrO2Cl2 + H2O
A mixture of chloroform, sulfuric acid and potassium dichromate is heated on a water bath.
2CHCl3 + K2Cr2O7 + 5H2SO4 ---> 2COCl2 + 2KHSO4 + 5H2O + Cr2(SO4)3 + Cl2
Chloroform is oxidized by potassium dichromate in the presence of sulfuric acid in order to prepare phosgene. Hydrochloric acid is removed by water.
(a) K2Cr2O7 + 4H2SO4 ---> K2SO4 + Cr2(SO4)3 + 4H2O + 3O
(b) CHCl3 + O ---> COCl2 + HCl |
Yes, I realize that the first equation states dichromate then says chromate within it. These were quoted from three separate entries in the
'Encyclopedia of Chemical Reactions'.
(3) On phosgene from carbon tetrachloride I found:
| Quote: |
Carbon tetrachloride reacts with sulfuric acid with kieselguhr as a catalyst.
(a) 3CCl4 + 2H2SO4 ---> 3COCl2 + 4HCl + S2O5Cl2
(b) CCl4 + S2O5Cl2 ---> COCl2 + 2SO2Cl2
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From the same book, interesting side products there.
(4) And on phosgene in general:
| Quote: | | The reaction between phosgene and water is completely irreversible yet there is evidence that phosgene could be kept indefinitely in contact with a
sufficiently concentrated hydrochloric acid solution. |
So it looks like if I just used a water trap it would stop working after a certain concentration of HCl was achieved in solution, better to use
corpious amounts of KOH then. The book that I got this information from quote some really old sources so the equations are usually not totally
correct, for example, the book has preparations for chlorine tetroxide and perbromic acid the 1890's but it is a good place to look for ideas.
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Eclectic
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Alkyl Carbonates
EP0638541 looks good. It reacts urea with a glycol (ethylene glycol: antifreeze) with a catalyst (almost anything apparently, the first example uses
zinc oxide). The product is reacted with a lower alcohol to form the desired carbonate.
[Edited on 20-11-2004 by Eclectic]
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