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halogenstruck
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oxalyl chloride by TCCA
routine: Dimethyl Oxalate=Chlorinating,UV==>Bis-trichloromethyl Oxalate=catalytic decomposition,heating=>(COCl)2 USpat 2816141
a variation to the method mentioned in this blog can yield aforementioned Bis-trichloromethyl Oxalate by TCCA and Dimethyl Oxalate
Attachment: Benzyl chloride.mht (1.1MB)
This file has been downloaded 46603 times
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Jor
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Bis-trichloromethyl Oxalate=catalytic decomposition,heating=>(COCl)2
Is the other product phosgene? If so, AVOID THIS REACTION!
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halogenstruck
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yes phosgene will produce but as it`s a gas it won`t liquify with oxalyl chloride.
even pure oxalyl chloride easily breaks to phosgene.
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Jor
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I hope you realise this gas is an ENTIRE other league than Cl2/NO2, and it is even MUCH more toxic than HCN, PH3, etc. This gas is so toxic that I
don't even feel safe at all in my home made fume hood, unless I use very small quantities. But you want to do this on a synthesis scale...
AFAIK exposures to 100ppm may give you a fatal dose within a minute... 5ppm is LD50 for 1 hour. Please rethink!
Try to get cyanuric chloride, and chlorinate anhydrous oxalic acid with it (look at Sauron posts, he gave lots of good advice on this route). Or make
the cyanuric chloride, this involves HCN and ClCN, but these are still much less toxic than phosgene.
In my opinion, a lot is possible in a home lab, I don't shy away from dangerous chemicals, like mercury salts, benzene, CCl4, hydrazine, arsenic, but
phosgene (and others very nasty ones like H2Se and nickel carbonyl) should NOT be used, unless less than a gram or two.
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DJF90
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I've seen an old preparation in a home lab book for nickel carbonyl. You're right that phosgene is toxic, but only twice as much as HCN...
SF4 is FAR more toxic (10x that of phosgene)... its a shame really, a very nice reagent for organic synthesis. Anyway.. I don't want to be undermining
the toxicity of phosgene, cos its pretty damn nasty... but, it could be absorbed (in toluene IIRC) for later use, and if you have a fume hood and work
in a sealed system (i.e. all joints greased, outlet tube lead through toluene and then through a solution to destroy any escaping phosgene) then I
don't think its out of range for the advanced amateur.
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entropy51
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Quote: Originally posted by Jor  | | When I distilled bromine once, and saw the deep red vapours red, it was an incredible sight, and was scared but at the same time amazed.
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Jor, phosgene is no more dangerous to work with than Br2. Br2 has better warning properties, but neither is
a big deal in a good hood. Practically everything discussed on this forum is potentially lethal, but mostly only if you don't know what you're doing.
If you don't, potentially becomes probably.
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Jor
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First phosgene is more than twice as toxic than HCN, maybe it is 2 times more toxic if you recieve the dose in a minute, after all HCN has a very
steep dose response curve, unlike phosgene.
Can you provide references for SF4 toxicity? I'd be interested to read it, as I have never heard of this gas. I agree that the gas can be used safely
in a good fume hood, but not many people on this forum have one... And unless you live on the countryside, I think it is not responsible to vent lots
of phosgene, so yes absorption is a must.
Oh and entropy, phosgene is much more toxic than Br2. I have worked inside with neat Br2 (with doors wide open and a blower blowing to the door) and
it was really unpleasant at times. I am still fine and I am sure i wouldn't have been with phosgene. Ofcourse those were my early unwise days 
But halogenstruck, can you buy cyanuric chloride? this chemical is really cheap and the best way of making oxalyl chloride. Or PCl5 can be used, but
that is hard to get, just like the P needed to make it.
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DJF90
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Jor, you take what Entropy says out of context... nowhere does he say that phosgene isn't as toxic as bromine (because its a fact that it is much more
toxic) but he says its "no more dangerous to work with" than bromine.
SF4 is a nasty gas, and it's synthesis can be found in Brauer. It is a commonly encountered molecule in Inorganic chemistry, as it has the C2v point
group, and its 19F-NMR spectrum is interesting (contrast between high/low temps - Berry pseudorotation). I don't have a reference for it, it's just a
fact I've remembered for a while, so if you want one you'll have to search for it. Synthetically it can effect the conversion of carbonyls to
gem-difluorides and carboxylic ester groups to trifluoromethyl. Of course, phenylsulfur trifluoride is a nicer reagent that can be used as a
substitute, but its still pretty horrid.
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Myfanwy
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many things are more poisonous than phosgene.
For example Perfluoroisobutene. this is made easy by pyrolysis of PTFE(teflon) and is 10 times more toxic than phosgene.
why dont bubble the phosgene in ethanol or lye?
i think this is very interesting, because TCCA, methanol and oxalic acid arent very hard to get for hobbychemists.
this is may the only option for me to get oxalyl chloride.
anyway i wanted for a long time to make phosgene. i just want to make this one time in my life.
are there some easier ways to make it? (dont have CHCl3,CCl4 etc)
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entropy51
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Then perhaps you can explain why the NIOSH
permissible exposure limit for both Br2 and phosgene is 0.1 ppm
I stand by my statement: | Quote: | | Jor, phosgene is no more dangerous to work with than Br2. Br2 has better warning properties, but neither is a big deal in a good hood.
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I have worked with both of them, at home and at work. If you had you would know that this is just basic
stuff. You will probably understand when you have a bit more experience. Until then, you could benefit by learning from those with that experience.
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mnick12
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| Quote: Originally posted by DJF90 | | I've seen an old preparation in a home lab book for nickel carbonyl. You're right that phosgene is toxic, but only twice as much as HCN...
SF4 is FAR more toxic (10x that of phosgene)... its a shame really, a very nice reagent for organic synthesis. Anyway.. I don't want to be undermining
the toxicity of phosgene, cos its pretty damn nasty... but, it could be absorbed (in toluene IIRC) for later use, and if you have a fume hood and work
in a sealed system (i.e. all joints greased, outlet tube lead through toluene and then through a solution to destroy any escaping phosgene) then I
don't think its out of range for the advanced amateur. |
DJF90-
Are you sure SF4 is 10x more toxic? I took a quick peek on wiki and saw that the health rating for sulfurtetrafluoride is only 3, http://en.wikipedia.org/wiki/Sulfur_tetrafluoride . Mabe you were thinking of disulfur decafluoride? According to wiki it is 4x more toxic than
phosgene, and had some use as a chemical wep http://en.wikipedia.org/wiki/Disulfur_decafluoride . I am not saying your wrong because I only know 2 mins worth of reading on these two
compounds, but does SF4 have some toxic effect wiki failed to mention?
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Jor
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Entropy, the permissible exposure limit says nothing about lethality. I2 and Br2 have 0,1ppm, Cl2 (more toxic than I2) 1ppm, HCN 5ppm (more toxic than
Br2), etc. Fact is that LD50 1Hr is 5ppm for phosgene and 192ppm for bromine.
I am interested how you worked with phosgene at home. Did you use a fume hood commercial or homemade? Or you worked outside? Interesting as I would
like to make some more CrCl3 from the hydrated chloride and this involves leading hot CCl4 over the material, and phosgene is formed.
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DJF90
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Jor: Anhydrous chlorides are best made by refluxing with thionyl chloride. On a separate note, a book I have here says this about HCN: "Although
hydrogen cyanide is an active poison, the reagent can be prepared in quantities up to 0.5kg without undue danger if a good hood is available and
proper care is taken". I think anything can be utilised in the home lab so long as adequate precautions are in place - of course 0.5kg HCN is a little
excessive, but 50g or so is more realistic for something I'd do if I had a hood at the moment.
mnick12: You're right, I've made a mistake. Its 2x more toxic than phosgene, which is 10x more toxic than HCN (IIRC), making SF4 20x more toxic than
HCN. Handling is a real bitch as it seems to react with glass and is gaseous at STP. It hydrolyses readily to give HF. Not nice stuff. Reference is
Feiser.
Entropy: I intend on making some diphosgene as a "safer" alternative, starting from methyl chloroformate. Thiophosgene is another reagent that I find
intriguing and would like to use some day. Diazomethane is another I'd like to utilise at some point.
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BromicAcid
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I work with phosgene and SF4 on a regular basis, but regarding phosgene, no, it's not horrible so long as you have the ability to contain and
neutralize it. These are the real issues here, any time you work with a poisonous gas you literally need to be able to do these things and have them
planned out otherwise you cannot go forward. If you're got that figured out, your problem is going to be separating it from your formed oxalyl
chloride. In my experience making chloroformates and other phosgene derivatives, even pulling under vaccum with efficent stirring is still
insufficent to remove all the phosgene, that stuff is tenacious, and unless you can shoot a TCD you'll never know for sure.
[Edited on 4/6/2010 by BromicAcid]
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entropy51
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| Quote: Originally posted by Jor | Entropy, the permissible exposure limit says nothing about lethality. I2 and Br2 have 0,1ppm, Cl2 (more toxic than I2) 1ppm, HCN 5ppm (more toxic than
Br2), etc. Fact is that LD50 1Hr is 5ppm for phosgene and 192ppm for bromine.
I am interested how you worked with phosgene at home. Did you use a fume hood commercial or homemade? Or you worked outside? Interesting as I would
like to make some more CrCl3 from the hydrated chloride and this involves leading hot CCl4 over the material, and phosgene is formed.
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Jor, as DJF90 pointed out, I didn't say phosgene was not more toxic than Br2, just that it was no more
dangerous to work with. Toxicity of vapors is normally expressed by the Haber product Ct, where C is concentration and t is exposure time, to produce
some effect such as 50% lethality. The key is to keep exposure time t = 0, which a good hood and effluent scrubber will do.
If I did chemistry outside, I would get a long vacation off the Florida keys. My hood is home made. We used tanks of phosgene at work, and I would
not try that at home. I make only small amounts and use it immediately in the reaction. If I were to do your prep, I would set it up so that the
CCl4 was pulled over the chloride by gentle vacuum and pulled through a caustic scrubber (bubbler). If the phosgene is under negative pressure
relative to the atmosphere, it cannot leak out before it enters the scrubber. I would not attempt it without a good hood.
@ Bromic Acid, you guys moved the Carbolabs operation to your shop, didn't you? I used to know those guys. They knew phosgene like nobody else!
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BromicAcid
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@ Entropy51, you knew the Bethany crew? Wow, talk about a small world! Yeah, they were the phosgene experts hands down.
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entropy51
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| Quote: Originally posted by BromicAcid | | @ Entropy51, you knew the Bethany crew? Wow, talk about a small world! Yeah, they were the phosgene experts hands down. |
Yes, I knew some of them many years ago. It is indeed a little place.
Oh no, you wouldn't!
Trust me. Most hateful stuff in the world.
[Edited on 6-4-2010 by entropy51]
[Edited on 6-4-2010 by entropy51]
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Jor
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| Quote: Originally posted by DJF90 | Jor: Anhydrous chlorides are best made by refluxing with thionyl chloride. On a separate note, a book I have here says this about HCN: "Although
hydrogen cyanide is an active poison, the reagent can be prepared in quantities up to 0.5kg without undue danger if a good hood is available and
proper care is taken". I think anything can be utilised in the home lab so long as adequate precautions are in place - of course 0.5kg HCN is a little
excessive, but 50g or so is more realistic for something I'd do if I had a hood at the moment.
mnick12: You're right, I've made a mistake. Its 2x more toxic than phosgene, which is 10x more toxic than HCN (IIRC), making SF4 20x more toxic than
HCN. Handling is a real bitch as it seems to react with glass and is gaseous at STP. It hydrolyses readily to give HF. Not nice stuff. Reference is
Feiser.
Entropy: I intend on making some diphosgene as a "safer" alternative, starting from methyl chloroformate. Thiophosgene is another reagent that I find
intriguing and would like to use some day. Diazomethane is another I'd like to utilise at some point. |
I know about the thionyl chloride route. But the problem is, thionyl chloride and PCl5 are like the ONLY chemicals I really want, but i can't buy. And
making it is a real hassle, I don't have the time for that. But I do have enough (350mL) of CCl4 so that's the way I go.
Yes, I have used HCN as well in my hood, I made a few grams to make some KCN. I am not very scared of HCN when you generate the few grams over a
pretty long period (hour), as your body quickly breaks it down, that's why 5ppm is upper limit for 8 hours, your body can easily break it down at this
concentration fast enough. I have heard you can consume up to a gram of KCN spread over a day without ill effects.
Lung irritants are different, they do their damage and your body is slower to heal.
But the problem with HCN, I don't know if I can smell it so I still avoid it, unless I need to make it, wich i don't anymore as I have enough KCN now.
I try to avoid all very toxic gases. The only toxic gasses I make in great quantities are HCl, NO2, HNO3. I dissolve metals very often to make
compounds, and I work with (boiling) aqua regia a lot lately. I my acid bottles getting empty quite fast lately, need to order some new ones 
The only toxic gasses wich have made me uncomfortable so far are phosgene and stibine, I have made both.
SF4 sounds like something scary, but not something that you would encounter often
Diazomethane You need some special glasware to handle this, or it might explode
right in your face 
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DJF90
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Not necessarily. I recall being lead to a paper that claims it can be safely done in ground glass apparatus, and even on a fairly grand scale.
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HamalachMichael
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| Quote: Originally posted by Jor | I hope you realise this gas is an ENTIRE other league than Cl2/NO2, and it is even MUCH more toxic than HCN, PH3, etc. This gas is so toxic that I
don't even feel safe at all in my home made fume hood, unless I use very small quantities. But you want to do this on a synthesis scale...
AFAIK exposures to 100ppm may give you a fatal dose within a minute... 5ppm is LD50 for 1 hour. Please rethink!
In my opinion, a lot is possible in a home lab, I don't shy away from dangerous chemicals, like mercury salts, benzene, CCl4, hydrazine, arsenic, but
phosgene (and others very nasty ones like H2Se and nickel carbonyl) should NOT be used, unless less than a gram or two.
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| Quote: Originally posted by Jor | I hope you realise this gas is an ENTIRE other league than Cl2/NO2, and it is even MUCH more toxic than HCN, PH3, etc. This gas is so toxic that I
don't even feel safe at all in my home made fume hood, unless I use very small quantities.
|
Exactly, the dangers of dealing with phosgene cannot be underestimated. Infact if you're not an experienced and skilled and knowledgable chemist with
access to a proper laboratory I would not even medle with that substance as you have expressed yourself in other words.
Anyone undergoing various procedures to produce a desired product ought to read carefully the MSDS (Material Safety Data Sheets) for each chemical
used in the procedures to be aware of the potential dangers and hazards to health and even one's own life.
Also the chemical reactions themselves and any potential byproducts of the various procedures ought to be known and investigated for any potential
dangers.
Also there is a danger of someone posting a method to produce a chemical substance, but would not be aware that some product could be formed that
where not even part of the method, such as the radical reaction of chloroform under the presence of UV light and oxygen. Given someone has not the
knowledge and has a let's say 100ml of chloroform stored in a clear 1 litre glass bottle that was left for several months over which phosgene would
accumulate and once such bottle would be opened it could be a potential Pandora's box. This is just a rough scenario and whether such would cause
potential danger would need further experimenting, the point is that such scenario is potentially dangerous and for this reason it is important to be
fully knowledgable before undertaking any laboratory experiment especially those less obvious that are not simple NaOH + HCl type reactions, though
even such a simple reaction has dangerous associated with it.
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HamalachMichael
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| Quote: Originally posted by Jor | | I know about the thionyl chloride route. But the problem is, thionyl chloride and PCl5 are like the ONLY chemicals I really want, but i can't buy. And
making it is a real hassle, I don't have the time for that. But I do have enough (350mL) of CCl4 so that's the way I go. |
PCl5 can be made using phosphorus and chlorine gas. P4 you can buy on ebay and chlorine gas you can produce yourself easily via various routes of
which one is the electrolysis of NaCl.
Then once you have the first chemical you want that is PCl5 you can use it to make thionyl chloride by reacting it with sulphur dioxide which you can
buy in a gas cylinder or produce yourself by the combustion reaction of elemental sulphur which you can buy cheap on amazon.
For someone like yourself that has made such killer substance as phosgene I understand not what is such a big hassle for you to make both PCl5 and
thionyl chloride according to the procedures posted above?
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careysub
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On the Relative Toxicity of Phosgene, Bromine, and HCN
A useful reference for addressing this issue is found here:
https://books.google.com/books?id=fRBhwEqijk8C&pg=PA274&...
(p. 274 of "Evaluation of the Effects and Consequences of Major Accidents in Industrial Plants" By Joaquim Casal)
He presents a set of parameters and an equation for evaluating the LC01 (lethal to 1% of the population) for all three of these chemicals for various
time periods (values in ppm).
Evaluating this for periods of 1, 10, 100, and 1000 minutes we find:
Phosgene (1 min) 384
Phosgene (10 min) 38.4
Phosgene (100 min) 3.84
Phosgene (1000 min) 0.384
Bromine (1 min) 1737
Bromine (10 min) 347
Bromine (100 min) 69
Bromine (1000 min) 13.8
HCN (1 min) 580
HCN (10 min) 183
HCN (100 min) 58
HCN (1000 min) 18
Another bit if data:
Threshold detection concentrations -
Phosgene: 1.0
HCN: 1.0
Bromine: 0.1
Intolerable concentrations -
Phosgene: none
HCN: none
Bromine: 10
Commentary:
The strict Haber product linear relationship exhibited for phosgene is due to it being a true cumulative poison, very little detoxification with
time*. HCN on the other hand has an efficient natural detoxification mechanism, that allows continuous exposure without any harm as long as exposure
stays below the rate of elimination.
From this data bromine appears not to be cumulative either, but unlike HCN it has a very low continuous exposure limit -- not due to its systemic
toxicity, but due to its intense sensory irritation. This is a notable difference for bromine compared to the others - it is a pungent, intense
irritant, and in fact will cause someone to flee rather than endure the exposure.
The other two are detectable at low levels, but can the odors can be concealed, and often the nose becomes desensitized and stops being able to detect
it. This does not happen with bromine.
Executive summary:
Phosgene and HCN are about the same in toxicity for very short concentrated exposures, but at all times longer than a few minutes phosgene is much
more toxic than HCN or bromine. The absence of any strong warning odor makes it very dangerous if not handled with excellent equipment. Except for the
possibility of a lethal exposure from a sudden dense bromine cloud, a lethal bromine exposure is virtually impossible since no one could tolerate it.
NB: The equation (or the parameters supplied) breaks down if stretched to extremes, the 18 ppm for HCN at 1000 minutes is actually below the level
that can be tolerated indefinitely due to detoxification.
(I have in the past been professionally employed in modelling toxic respiratory exposures, BTW)
*The time scale on which phosgene detoxification occurs is on the order of a week. Lethal exposures can be accumulated over the course of several
days. This phenomena was observed in WWI.
[Edited on 20-9-2015 by careysub]
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softbeard
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| Quote: Originally posted by HamalachMichael |
For someone like yourself that has made such killer substance as phosgene I understand not what is such a big hassle for you to make both PCl5 and
thionyl chloride according to the procedures posted above? |
I don't think you should be encouraging Jor to produce PCl5 and SOCl2 through the synthesis routes you've outlined.
Jor may not have proper materials for handling these materials at hand. Each of these substances, PCl5, SOCl2, COCl2
is unique and requires unique handling. Lumping them all together as acidic lung irritants, and saying since he's handled the worst of the bunch
('killer' phosgene) means that he's ready to prepare the other chlorides is IMHO wrong.
Even PCl5, and through it's hydrolysis product POCl3, can produce pulmonary edema if not handled properly. SOCl2
(though I think is far more benign to your lungs compared to the others chlorides in this list) can cause all kinds of corrosion problems in any metal
(esp. iron/steel) tools or machines exposed to the vapours.
You know, further up this thread is a post by Myfanwy from 2010. As I understand it, he had a bit of a lackadaisical attitude towards phosgene. I do
not claim to know the details of his passing, but I believe it involved phosgene.
My point is, each one of these chemicals and their precursors have their unique properties that have to be respected. I'm by no means a chemical
alarmist, but there can be a very fine line with some of these materials and you must show them respect. Stay safe.
Edited to assign proper quotations
[Edited on 20-9-2015 by softbeard]
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softbeard
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Thanks, careysub. I think that is excellent information on the relative toxicities and gives you a rough quantitative handle as to how much release of
the materials is you've listed is tolerable. The comparison to Br2 is very interesting as a reference point.
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x3110n
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The title says: "oxalyl chloride by TCCA", now, tell me again; why are we discussing the toxicity of stibine, phosgene, HCN and all this?? This has
nothing to do with the prep of oxalyl chloride by TCCA!
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