Sauron
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Cl2 + CS2 -> four very useful compounds
This is a very simple and highly productive reaction that directly produces two comounds that are both very useful.
They are both nasty smelly corrosive liquids.
One is sulfur (II) chloride.
The other is perchloromethyl mercaptan, or trichloromethyl sulfenyl chloride.
I will post attachments detailing the reaction, but first let me explain what you can do with the products:
1. Perchloromethyl mercaptan is mainly used to make CCl4 by reduction with iron filings under reflux.
It can also be reduced to methanefulfonic acid or mesyl chloride.
Or it can be reduced to thiophosgene, which is very handy for making certain transformation.
The CCl4 can be reduced to CHCl3 with wet iron filings.
2. As will be seen the improved modern process for chlorinating CS2 using granular AC bed at a regulated temperature (the chlorination is exothermic)
produced not a mixture of SCl2 and S2Cl2 which is difficult to fractionate from the CCl3SCl but only the desired form, SCl2 low boiling (58 C)easily
seperated.
SCl2 is useful as a chlorinating agent for carboxylic acids to acyl chlorides and acid anhydrides.
Now note, CS2 can be made from carbon and sulfur so this is one of those process streams that really can't be regulated effectively.
CS2 is volatile and very very flammable.
CCl3SCl is toxic and an obsolete war "gas" (but it is liquid.)
C(S)Cl2 is also toxic and an obsolete war "gas" (liquid).
SCl2 and S2Cl2 are corrosive fuming liquids.
MeSO2H and MeSO2Cl are toxic and carcinogenic.
CCl4 is toxic and so is chloroform.
And I shouldn't have to remind that Cl2 is toxic and another obsolete war gas.
Still there's a lot of useful material in this stream. Anyone interested?
[Edited on 8-2-2007 by Sauron]
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Sauron
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Here are two US patents from the 1970s to AKSO and a Synthesis (Thieme) article (in German) by same chemists describing same process. The article has
illustration of bench scale setup while patent is on industrial scale. However, it is erasy to correlate the two.
Basically a slow trickle if CS2 is fed through a jacketed column packed with a bed of GAC and mixed with a slow stream of Cl2 gas, the column being
cooled with water to a moderate temperature.
SCl2 and CCl3SCl collect below. No S2Cl2 forms and this facilitates fractionation as the bp's are nearly 100 C apart.
[Edited on 8-2-2007 by Sauron]
Attachment: s-1971-21761.zip (1MB)
This file has been downloaded 407 times
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garage chemist
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If you tell us how to make CS2 this would all be of good use to us.
There is an extensive thread on CS2 synthesis here and so far nobody here has succeeded in making it! Ask Bromic.
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Sauron
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That's odd. After all it clearly does work on an industrial scale and has for hundreds of years. I will have to go read that thread.
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Organikum
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If one has the means and some skills then industrial processes can very well be applied by the amateur.
Whereby much of the recently published academic stuff done on minimol scale and products identified by GC but never isolated is completely worthless -
more chemical masturbation then actual chemistry.
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Sauron
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@GC
Calcium carbide becomes incandescent in sulfur vapor at 500 C forming calcium sulfide and carbon disulfide.
That is a relatively low temp compared to the usual ones for C and S rxn. Maybe worth a try.
CaC2 + 5 S -> CaS + 2 CS2
Maybe not as economical as charcoal and sulsur but on the other hand if that one does not work...
No H2S produced. One is still left with the condensation of very hot CS2 vapor, life's a bitch. Lots and lots of heat exchangers. Ending with dry
ice/ethanol or some other freezing mixture.
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garage chemist
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I once heated CaC2 with sulfur in a test tube until the sulfur boiled, nothing happened. Is it not possible to lower the reaction temperature a bit to
allow it to occur in the liquid phase?
Gas- phase reactions, especially when the gases have to be heated, are just so damn inconvenient on a small scale.
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Sauron
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Not that I am aware of, but then how to you lower heat of reaction? Find a catalyst.
I found this reaction in the 1911 Encyclopedia Online. So it is an old reaction, and there ought to be lit. on it.
Other carbides might give same rxn but, I suspect CaC2 is br far the cheapest carbide available.
One approach that wouldsidestep the problem of dealing with all that hot CS2 vapor and also the mechanical difficulties of vapor phase S reactions
would be to do this in an autoclave (Parr pressure reactor) capable of 500 C. These are available in lots of sizes, and rated for up to several
thousand PSIG. Follow the rxn by watching the pressure rise, then cool it down finally chilling it and take off your liquid CS2. Sure there's capital
cost of the reactor but, you eliminate the capital cost of all that heat exchange and condensation system, and also the sulfur vaporizer. Second hand
Parr vessels and other pressure reactors can be had on LabX and the used market. I would not contemplate buying one new.
------------
Different approach, and I am going on pure memory here, but I seem to recall that an old process for making CS2 was roasting iron pyrites with
charcoal. Pyrites are just iron sulfide, right? And cheap. Maybe that works better than elemental sulfur?
[Edited on 8-2-2007 by Sauron]
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Sauron
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If the slow trickle of CS2 and slow feed of Cl2 to column bed of GAC does not appeal, the same rxn can be accomplished by a one-pot chlorination of
CS2 in the presence of iodine.
As long as the temperature is kept in the recommended range 20-30 C the rate of Cl2 addition, or consistency of same is not critical. You just
chlorinate till a specified increase in volume (2X) has occurred. Then you let the product sit for 2 days. This improves the yield.
The procedure must not be conducted in sunlight.
Sunlight, temp over 50 C and overchlorination are conditions favoring formation of CCl4. You are better off making your CCCl4 (if that is your target
rather than thiophosgene) after seperation of the sulfur chloride.
The product will contain CCl3SCl, SCl2 and S2Cl2. In order to convert the S2Cl2 to SCl2 ithus facilitating fractionation, you simply pass the mixture
through the GAC bed under conditions specified by Rpp and Meyer (see above) and you will have only the perchloromethyl mercaptan and SCl2.
A JACS article detailing this procedure is attached.
[Edited on 8-2-2007 by Sauron]
Attachment: ccl3scl.pdf (278kB)
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Sauron
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Thiophosgene
C(=S)Cl2
was a failure as a WWI war gas because unlike phosgene it is non-insidious. You KNOW when it is around. Also it is a high boiling liquid whereas
phosgene has a bp just over 0 C.
Here's a review of thiophosgene's versatile chemistry -- and by the way this is not a CWC listed compound.
[Edited on 8-2-2007 by Sauron]
The Org.Syn. prep of thiophosgene is not very efficient and the apparatus described would require an enormous fume hood, probably 3 m wide walk in
style.I included this prep for comparison in the attached zip file.
A Synthesis (Thieme) article and two US patents by same chemists as the CCl3SCl work above, Rupp and Meyer at AKSO, is much better. CCl3SCl is fed
slowly through a heated fixed bed of silica gel having particular properties specified. The products are (just as in the Org.Syn. prep) thiophosgene,
molten S and a lot of hot angry H2S which after the thiophosgene has been condensed, is trapped in an oversized caustic scrubber. The molten S
collects in a flask at the bottom of the column.
[Edited on 8-2-2007 by Sauron]
[Edited on 8-2-2007 by Sauron]
Attachment: s-1978-24896.pdf (1.3MB)
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BromicAcid
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Sauron, I have never heard of the method involving the use of calcium carbide (as far as I can remember) for the preparation of
CS<sub>2</sub> but it sounds interesting. As far as the iron sulfide method, I have heard of that as well but IIRC the temperatures
involved are somewhat prohibitive. My success with the Carbon/Sulfur method have been dismal at best. NBK left a comment on my site regarding my
setup
"Regarding the CS2 synth, the old processes used all iron pipe fittings, with the carbon being heated to redness before sulphur lumps were dropped in
on top via a long tube sealed with a ceramic plug
The preheating would seem to prevent the sulfur from subliminating before it could react, as it did in your experiment."
Makes sense and I would have acted on it too if I had more time to experiment. Then there is the propane method which was going to be one of my next
experimental things but that never got off the ground either. And my asphaltum method which also never got a run. Gahhh! I wanted
CS<sub>2</sub> and CCl<sub>4</sub> so bad!!! It's interesting to know what I could have done should I ever get some
CS<sub>2</sub>. What we need are more people out there experimenting to prefect a method of preparation but that is a fact best suited to
the CS<sub>2</sub> thread.
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Sauron
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@BromicAcid, thanks much. I also suffer from an overabundance of projects and insufficiency of time.
CS2 is one of those deceptively simple compounds that one takes for granted,, like, it's just a solvent, right? Wrong. And same goes for CCl4. In both
cases the reactions they are capable of surprise and astonish.
You know about the rxn of CS2 with Na metal shavings? It condenses to a heterocyclic ring system, who would have thought? A few more trnformations,
one of them involving a potassium xanthate - again from CS2 - and you have the tetrathiafulvalene system, C8128S8 and all those electrons on the
sulfurs all in a charge couple complex. The basis of organic superconctivity. Just as an example.
And the Luddite environmentalists are out to banish CS2 from the globe. What nonsense.
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Fleaker
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@ Sauron/Bromic
I apologize for being lazy about it, but what are some of the high temperature routes to go about this? Having a melting furnace to 1750C and a tube
furnace to 1200 I'd like to try out these methods. This has definitely piqued my interest as it seems more of an engineering issue to make a system
for its synthesis. And no, I didn't know about the reaction of CS2 with sodium, that is very interesting.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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Sauron
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I guess we ought to get the CS2-making thread (quite extensive) going again rather than trying to rehash all that in this one.
As to the CS2 rxn with sodium, I mentioned that in a couple of threads on other topics a while back. But I will at least sketch this (final) structure
and post it here as it is lovely. The crystals are reported to be a very nice deep red color.
There are two Org.Syn. procedures concerning this. One is the condensation with sodium and the other, a different route to same system. There were
explosions reported when attempting the condensation with potassium so some workers felt that it was prudent to regard all alali metas with CS2 at
potentially hazardous.
[Edited on 9-2-2007 by Sauron]
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Sauron
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Here's a zip file of the two Org.Syn. articles on this C8H8S8 system.
The first starts with CS2 and does not quite go all the way to the final coupled system.
The second is an alternative route that avoids reacting CS2 with a bunch of Na shavings. Supposedly the product is cleaner. Also they pointed to some
explosions reported with the other procedure but in fact those were only with potassium shavings and not with sodium at all. I would stick with sodium
if I were to go that route, but actually I plan to proceed the other way.
The alternate route starts with condensation of ethylene dithiol and chloroacetyl chloride. I have to make the acid chloride as it can't readily be
shipped (requires refrigeration.) I already bought the extremely stinky and headache inducing dithiol.
[Edited on 9-2-2007 by Sauron]
Attachment: CV9P0203[1].zip (302kB)
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Sauron
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Another useful and productive chlorination is that of methyl thiocyanate.
The yields from 100 g of MeSCN the following mixture:
cyanuric chlorice (solid, crystals) 65-70 g
Fract. 1 thiophosgene/CCL4 mixture (approx 2:1 on molar basis) bp 70-74 C up to 50 g
Fract. 2 perchloromethyl mercaptan bp 148-150 C Main cut, 84 g after working up Fract 1 with further chlorination
Fract. 3. bp >200 C unidentified mixture, small qty, containing some cyanuric chloride.
While some have called this of no preparative value, I do not agree. Fractions 1 and 2 represent the product stream of this thread, and this prep
makes them accessible to those who cannot obtain CS2.
James gives the overall reaction as
3 CH3SCN + 11 Cl2 -> 2 CCl3SCl + C(=S)Cl2 + Cl3(CN)3 + 9 HCl
CCl3SCl can be converted to CCl4, or to C(=S)Cl2, or to MeSO2Cl.
CC (TCT) is a useful byproduct hard to obtain in Europe where it is rated as highly toxic (T+).
The Fraction 1 is mostly thiophosgene and many of its reactions can be conducted in CCl4. I bet it can be seperated efficiently by LC (gravity or
HPLC) techniques not available at the time of James.
Methyl thiocyanate can be prepared easily. The classical methos (cited in Merck Index) is from the action of dimethyl sulfate on aq barium
thiocyanate. I suspect that other methylating agents such as iodomethane ought to work. Sure enough Vogel p.301 confirms, alkyl halides and KSCN or
NaSCN in 95% ethanol give alkyl thiocyanates.
Perhaps this is a good employement of a MeCl generator from CC and MeOH.
[Edited on 9-2-2007 by Sauron]
Attachment: sau[1].pdf (193kB)
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garage chemist
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The synthesis of CS2 might be doable on a small scale in a microwave.
Charcoal absorbs microwave energy very efficiently and reaches temperatures in excess of 1000°C which is enough to react with sulfur.
One could fill a test tube with a sulfur-charcoal mix for a few cm and then with pure charcoal for the rest.
The sulfur will be evaporated in the mix and rise as vapor through the microwave-heated charcoal. The vapors are withdrawn at the
opening of the test tube and led into a high-boiling chilled absorption oil, like kerosene, from which the CS2 can then be fractionally distilled
afterwards (the industry does it this way, instead of using strong cooling devices).
I really need to set up my old microwave for experimentation. There are numerous other high- temperature processes, including phosphorus synthesis,
that can be done with microwaved charcoal as the heat source.
[Edited on 9-2-2007 by garage chemist]
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Sauron
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That might be useful for process development but if folks need CS2 as a solvent or reagent then I'd say that 1 L a day is about the least you'd want
to be able to produce. That does not sound like MW scale to me. What sort of pot charge can you get into one of those?
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Sauron
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If making CCl4 is your goal and you don't want to, or can't, deal with CS2 and various stinking sulfur containing intermediates, here is another
related, but sulfur free route.
An artile from JACS posted in another thred (propionyl chloride) mentions that trichloroacetyl chloride and dichloroacetyl decompose to CCl4 in the
following manner:
CCl3COCl -> CCl4 + CO
I suppose CHCl2COCl decomposes to chloroform and CO? Because otherwise where does th extra Cl come from?
These acids are (1) easy to prepare (2) commercially available, and the inexpensive means to convert them to acid chlorides are at hand (TCT, or
benzoyl chloride).
In the JACS article, q.v., about half of the expected yield of trichloroacetyl chloride ended up as CCl4 instead.
If conditions were optimized for this decomposition then pure and sulfur free CCl4 would be accesible this way.
A catalyst might also be useful but it appears this extrusion of CO occurs on its own even when not desired.
CCl4 prepared from CCl3SCl is always contaminated with organosulfur compounds, requiring purification.
But from polychloroacetyl chlorides no S is present so no S can be in the product. Fractionation should suffice. Washing with bicarbonate would
convert any acid chloride remaining to the acid (solid) so then drying and simple distillation would give an extremely pure CCl4.
Interesting?
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Sauron
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I looked up some prices to get a feel for economies with this idea.
Chloroacetic acid $29/Kg or as little as $22/Kg if you buy a case of 6.
Dichloroacetic acid $79/L = 1560 g. So c.$50/Kg
Trichloroacetic acid $49/Kg
I would say, not worth saving $20/Kg to chlorinate chloroacetic acid to the higher substituted acids.
Just buy.
If economy or other issues dictate, then chlorinate glacial acetic acid to the desired product, this required sunlight or UV and is a rather slow
process.
MeSCN at least from Acros is packaged in 100 ml bottles @$39 so unless I find a cheaper supplier in larger qty I would not buy but make. If MeCl in
EtOH + KSCN will work, then MeSCN will be quite cheap to make as MeCl is easy to generate from TCT and methanol.
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