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Sauron
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Apropos "SBr2":
Roscoe & Schorlemmer, A Treatise on Chemistry Vol. 1 (1881) state that S and Br2 form only a single compound, S2Br2, bp c.200 C, which they call
brimine disulfide. They state that it is far more unstable than the corresponding chlorine compound and that repeated distillations will decompose it
completely to the elements.
I suspect that it can be distilled succesfully in vacuo without decomposition.
It is prepared by treating sulfur with a slight excess of bromine and then removing the excess by passing dry CO2 through. It is described as a ruby
red liquid.
I am now checking Mellor Vol 57 on sulfur (1930). As usual Mellor very thoroughly recites the literature of the compound. Full references are
supplied. The upshot is much the same: S2Br2 only. Occasionally investigators claimed SBr2 or SBr4 but, no one could replicate their work and such
claims were disputed. Physical methods are emphasized for determination of the properties of S2Br2 to characterize it as a singular compound and not a
mixture. The great tendency of sulfur to dissolve in S2Br2 undoubtedly was the source of much of the controversy.
I attach the section from Mellow, with references, in full.
So between 1880 and 1930 very little had changed regarding the interaction of sulfur and bromine. I do not have Gmelin's Sulfur, which would be much
more current, but I seriously doubt that the situation has changed. Certainly Brauer makes no mention of SBr2.
It would be arrogant to rule out SBr2 as a possibility but, in absence of any literature consensus on its existance, I doubt that it exists.
Interestingly, thus far I have failed to find any supplier of S2Br2.
And in the process I have noticed that sellers of SCl2 and S2Cl2 are fewer and fewer, probably due to CWC.
[Edited on 5-9-2007 by Sauron]
Attachment: Pages from Mellor_ACTITC_S_v10_ch57_1930.pdf (207kB)
This file has been downloaded 1108 times
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kazaa81
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From the CRC Handbook of Chemistry and Physics, 87th edition :
Sulfur Bromide
Chem. Formula SSBr2
CAS #: 13172-31-1
Mol. Weight 223.938
Form. red oily liquid
M.P. -46°C
B.P. >25°C
Density 2.63 g/cm^3
Reacts with H2O
Hope this helps
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Sauron
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That's S2Br2, only they got the bp way wrong.
Mellor gives values for bp without decomposition at various reduced pressures.
Roscoe & Schorlemmer say 200 C approx at 1 atm.
So I would say that ">25 C" is far too vague and if they wanted to hedge they should have appended with partial dec.
But, anyway.
I would write that as Br-S-S-Br rather than S-S-Br-Br
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Sauron
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If anyone wants ask ask why S2Br2 is so interesting, at least to me, it is a reagent in the preparation of Ac2O (acetic anhydride) from anhydrous
sodium acetate.
The usual procedure is to add the bromine and the sulfur slowly, forming the S2Br2 in situ with the NaOAc, but I think this is clumsy and preforming
the S2Br2 may be better.
I am not certain that this makes more sense than preparing AcCl and reacting that with NaOAc, but, I'd try both.
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Sauron
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Looking back into earlier studies of mine on sulfur chlorides, here are the fundamentals:
The chlorination of sulfur (usually molten) with dry chlorine produces primarily S2Cl2 which is usually contaminated with dissolved chlorine and
dissolved sulfur, and some SCl2.
Upon fractionation, pure S2Cl2 can be obtained as a golden-yellow liquod of bp 149.6 C. S2Cl2 is stable.
Continued chlorination of S2Cl2 will produce SCl2, a dark red liquod boiling at 58 C. SCl2 is not stable and will disproportionate in a few days to
S2Cl2 and Cl2. This can be slowed by addition of a small percent of PCl3. An Akso patent to Rupp and Meyer describes a simple process for
quantitative conversion of S2Cl2 or mixtures of S2Cl2 and SCl2 to be converted to SCl2 by passing slowly through a fixed bed of slightly heated
granular activated carbon saturated with Cl2 and hgeated to a little above ambient. (c.60 C). This is a convenient method for preparing SCl2 when
needed.
This process is of important in the preparation of derivatives of perchloromethyl mercaptan, or trichloromethylsulfenyl chloride. Such derivatives are
carbon tetrachloride and thiophosgene.
Chlorination of CS2 produces a mixture of Cl3CSCl, S2Cl2 and SCl2 along with a little CCl4 and dissolved Cl2 and unreacted CS2.
The S2Cl2 is a great complication in the fractionation of this mixture since its bp is very close to that of the mercaptan. So the Rupp & Meyer
process greatly facilitates the seperation of the mixture by converting all the S2Cl2 to SCl2.
Once fractionated the Cl3CSCl can be reduced with iron filings to CCl4 or by other reagents to thiophosgene for making isothiocyanates.
The SCl2 can be converted back to pure (and stable) S2Cl2 which can be used to make Ac2O by reacting with anhydrous NaOAc then distilling.
The CCl4 can be employed as a solvent and has many other uses. Or it can be converted to CHCl3.
I regard chlorination of CS2 as a VERY productive process.
Essentially all that is required is dry chlorine and CS2, the temperature should be held to 30 C and absolutely not over 50 C and chlorination
continued till the CS2 has doubled in volume and mass. Avoid direct sunlight.
The initial crude reaction mixture will contain a lot of dissolved Cl2 and should be left for 24-72 hours. STENCH! as the sulfur chlorides and the
mercaptan are very irritating. Conduct all of this work in a GOOD HOOD. It is well worth noting that perchloromethyl mercaptan was BRIEFLY used as a
"war gas" in WWI by the French but abandoned as ineffective. The same is true of thiophosgene. They are obnoxious and toxic but you would not be able
to stand the smell long enough to be in danger. HOOD and SCRUBBER please or you will offend the neighbors. Protective gear for yourself.
This is a fine way to prepare feedstocks for CCl3/CHCl3, and Ac2O or thiophosgene and its derivatives.
VAST quantities of the sulfur chlorides used to be produced in exactly this way as byproducts of CCl4 manufacture but as carbon tet has gone out of
fasion and has become P.I., so have the sulfur chlorides. They are still of importance in the vulcanization of rubber.
Brauer has good procedures for SCl2 and S2Cl2. Anyone wanting references on the chlorination of CS2 and seperation of products, PM me. Others have
described efficient chlorine generation and scrubbing out traces of moisture from the Cl2 stream. UTFSE. Basically it is a matter of a chain of wash
bottles with conc sulfuric acid and appropriate safety precuations.
Another use for the sulfur halides:
You can use them to make thionyl chloride by oxidizing them with the SO3 you make from pyrolyzing ferric sulfate. Brauer teaches how.
You can also get to thionyl chloride by trating SO2 with phthaloyl chloride, if your supply of SO2 is up to the task.
Thionyl chloride is another politically incorrect chemical and for the same reason: as with the sulfur chlorides, the powers that be are afraid
someone might follow THEIR examples and make sulfur mustard with them.
Personnaly I wish the governments would work off their bad karma some other way and leave chemists alone.
[Edited on 9-9-2007 by Sauron]
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garage chemist
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Whats with the chlorination of CS2 to produce CCl4 as the desired product? Ullmann makes no mention of any intermediates isolated, just chlorine and
liquid CS2 with FeCl3 catalyst, and fractionation of the CCl4 and S2Cl2 afterwards. Does CCl3SCl further react with chlorine to CCl4 and S2Cl2 when
FeCl3 is present?
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Sauron
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Check out the bp's of S2Cl2 and CCl4S
They are too close to efficiently fractionate.
If you overchlorinate, say to triple starting volume of CS2 then CCl4 predominates, particularly in presence of direct sunlight and when temp is
allowed to exceed 50 C.
However if you stick to <50 C (preferably <30 C) and diffuse light, and 2X volume, you get SCl2/S2Cl2 and CCl4S (CCl3SCl).
So it is necessary to convert the S2Cl2 to SCl2, which boils 90 C less than the others, and then fractionation is very easy.
Once you have CCl3SCl isolated you hit it with Fe filings and you get CCl4. It is necessary to do this thoroughly in order to get rid of all the
mercaptan which otherwise is responsible for bad smell and toxicity.
Would you like the Rupp and Meyer articles and patents (Akso) and the older articles on the mercaptan? Sartori also has good info.
Once you have the SCl2 out it will of course start to disproportionate back to S2Cl2. You can drive SCl2 all the way by further chlorination, and once
you have pure S2Cl2 (two fractionations) it will stay that way.
The point of isolating the mercaptan is to have the option of either CCl4 or thiophosgene. If you only are after CCl4 then you have other choices, but
the problem of S2Cl2 remains,'
For an idea of the mess you can get into without Rupp & Meyer see the Org.Syn. prep of thiophosgene. Note that their apparatus is too large even
for my 2.5 meter wide, 1 meter high (internal) hood, but doing this outside of a hood would be stupid.
I can pull together my documentation and put it up on 4shared for you if you like.
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Cat_got_my_tungsten!
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That is one hell of an experiment. Nice one woelen, nice one.
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