I did an experiment, in which I added solid powdered sulphur to liquid bromine (no water involved, pure bromine). I really was amazed how much sulphur
dissolves in the bromine . I kept on adding sulphur, till no more dissolved.
And that is quite a lot, relative to the volume of bromine!
Finally, I obtained a clear transparent red liquid, having a much lighter color than bromine. This liquid has no brown vapor above it, and it also is
not corrosive to metals and plastics. The liquid has an extremely foul smell, absolutely different from bromine. No stench or irritation of the
throat, but very foul smelling.
I added some of this liquid to acetone. It dissolves in the acetone, giving a yellow liquid. After a while, the acetone starts fuming (just like a
concentrated solution of HCl). The fumes gives dense white smoke with ammonia.
My question is, what could the red liquid be. If you have (access to) bromine, then I really want to invite you to do this experiment. It is quite
funny and remarkable. If someone knows what happens, then that would be nice. My books tell me that sulphur and bromine form some compounds, but
require harsh conditions for reaction. Well, I just did the thing at room temperature. I really think that the sulphur and bromine reacted, otherwise
there would still be dense brown/red vapor of bromine above the liquid. I put some of the red liquid in a closed vessel, and no brown vapor can be
observed at all.
[Edited on 3-5-07 by woelen]nitro-genes - 3-5-2007 at 10:51
Addition of bromine to acetone would produde bromoacetone and HBr as well. Sulfur chlorides are pretty soluble in toluene or chlorinated hydrocarbons
IIRC, so you could add a little of the liquid to some tri,- or tertrachloroethylene solvent to be sure. If no sulfur precipitates, it should be pretty
pure S2Br or SBr2. Maybe this could be use to purify the sulfur bromide as well...
This reminds of a somewhat exotic energetic material that I haven't produced yet, nitrogen sulfide, or N4S4. It can be synthesised by bubbling dry
ammonia gas through a solution of SCl2 in toluene, in which the nitrogen sulfide isn't very soluble but SCl2 is. Maybe a similar compound could form
from S2Br2 as well. It is a rather sensitive yellow/orange coloured explosive, so I would keep quantities to a minimum...
[Edited on by nitro-genes]Maya - 3-5-2007 at 10:52
Dibromodisulfane S2Br2
I.
2 S + Br2 = S2Br2
64.13gr 159.83gr 223.96gr
The procedure is based on that described by Ruff and Winterfield. Thus, 94 ml. of Br3 is slowly added to 119 g. of S (recrystallized from CS3) in a
dry 500-ml. pressure flask capable of withstanding 20 atm. of internal pressure. (If proper precautions are observed, a beer bottle can be used.) The
mixture is heated for two hours on a steam bath. The dark-red liquid product is distilled at 0.1 mm.
The first cut contains primarily unreacted Br2; the main fraction distilling between 46 and 48°C is pure S2Br2, while crystalline S remains in the
distillation flask.
The yield averages 80%
SYNONYM:
Disulfur dibromide. Older names "sulfur monobromide" and
"sulfurous bromide."
PROPERTIES:
Dark red, oily liquid which does not wet glass. M.p. —46°C;
dissociates on heating into the elements and therefore can be distilled without decomposition only in high vacuum, d. (20°C) 2.629. In HSO,
hydrolyzes to HBr, SOa and S. Soluble in CS3, CCl4and C6H6«
[Edited on 3-5-2007 by Maya]woelen - 3-5-2007 at 11:13
Hmmm... strange. Your procedure also requires fairly harsh conditions (around 100 C plus high pressure), while I just added solid sulphur to bromine.
No heat involved, the sulphur just dissolves and no vigorous reaction can be observed.
Also remarkable is that you mention that the liquid does not wet glass. In my first post I was thinking of writing that as well, but I skipped it,
because bromine also does not wet glass. But now you mention this, it makes me more confident that I made some S2Br2.S.C. Wack - 3-5-2007 at 12:29
It may not be necessary. Mellor has a chapter on this in the sulfur volume, and gives refs of interest if you have potential for faith in 190- Ber.
and Z. anorg. investigators.Sauron - 3-5-2007 at 13:52
Assuming that S2Br2 behaves anything at all like SCl2 and S2Cl2, then sulfur will be very soluble in it.
SCl2 for example will dissolve 60% of its own mass of sulfurl. This is a problem when attempting to prepare sulfur chloride(s) from the elements and
is the reason that in any distillation the inside of the pot, column, etc are covered in deposited sulfur.
A cleaner and less ambiguous route to SCl2, by the way, is the interaction of Cl2 and CS2 on activated carbon in a cooled fixed bed (jacketed column)
at 40-60 C. This produces a mixture of SCl2 without any S2Cl2 and CCl3SCl, perchloromethyl mercaptan, which can be easily fractionated. The latter
substance is readily reduced with iron filings to CCl4 which is useful. If you merely bubble Cl2 into CS2, 2hich works, you get a ternary mixture
containing S2Cl2 as well, and that is not readily seperated because the bp of S2Cl2 is quite close to CCl4. However if you percolate that mixture
through GC bed with temp control, the S2Cl2 is entirely converted to SCl2. The Rupp/Meyer patents on this and related articles I have posted
previously.
I suspect that CS2 and Br2 would react analogously. CBr4 is also useful.
You might recall that S + Br2 + anhydrous NaOAc is a method for making Ac2O by in situ generation of S2Br2. This proceeds via acetyl bromide.
Naturally, Br2 is a bit too dear for this to be economically competitive with some other routes to AcCl/Ac2O.not_important - 3-5-2007 at 18:33
Mellor's says that "sulfur monobromide" can be made by dissolving sulfur in bromine, just STP, and that it resembles the chloride.Sauron - 4-5-2007 at 00:36
My recollection was that in the nineteenth and early 20th centuries there was endless wrangling over the sulfur halides, because SX2 and S2X2 are both
produced by union of the elements, the two can disproptionate, and despite very different bp's are hard to fractionate for that reason, plus
fragmentation back to the elements. Elemental analysis was complicated by any dissolved excess sulfur which led to erroneous claims of some fulfur
halides of different formulae. All this means that apart from the ambiguous older nomenclature, the older literature can simply be misleading.
A great deal of study went into the sulfur chlorides in commection with the US/UK ethylene based process for making mustard "gas". Also as a
consequence of the industrial importance (now fading) of carbon tetrachloride and the necessity of its purification from sulfur chloride byproducts.
And also for its use in the oleym process for manufacture of SOCl2 which often uses mixed SCl2/S2Cl2 simply because they are or were such a pain to
seperate, pre-Rupp/Meyer.
Brauer has pretty good and unabiguous procedures for the sulfur bromides as I recall. I'll go take a look.
How easy is it to liberate the bromine from your red solution woelen?Maya - 4-5-2007 at 09:33
S2Br2 + Br2 ---> 2SBr2
And
2SBr2 ---> S2Br2 + Br2
Totally reversible!
But your question is invalid since he used an excess of S8 in his experiment.
You would have to use an excess Br2 to be able to liberate Br2
woelen - 5-5-2007 at 14:21
Quote:
Originally posted by DrP
How easy is it to liberate the bromine from your red solution woelen?
The bromine does not go out of this red liquid/solution, not even on careful heating. I hope to find some time tomorrow to do more extensive testing
with stronger heating, and then I will let you know about that. But at room temperature and a little above that, there absolutely is no bromine vapor
at all, just the horrible smell.Eclectic - 5-5-2007 at 18:13
See if it is electrically conductive. I wonder what you would get if you electrolyzed this with AcOH? Could you regenerate the Br in situ?Sauron - 5-5-2007 at 18:38
@woelen, did you keep track of the relative masses of Br2 and S8 you combined?
My gess is that what you have is impure S2Br2 containing excess sulfur in which silfur is very soluble.
The main use of sulfur chlorides is as solvent for sulfur in vulcanization of rubber.
Contrary to @Maya's post, sorry to say, there does not seem to be any such animal as SBr2, at least not in Mellow or Brauer.
So the problem is, how to purify your S2Br2 to a definite state if that is what you want to do?
Are you set up for vacuum distillation? (The stuff stinks like hell as you well know.)
You might consider taking it down to the freezing point (-46 C) and seeing if any sulfur ppts out, then you can decant it. Or add more Br2 drop by
drop and wait between drops for reaction. Tedious, but eventually you might have slight excess of Br2 rather than excess sulfur.
Strong heating inadvisible as the stuff disassociates.
Brauer recommends fractionating at 0.1 torr. Unreacted Br2 comes over first (protect your pump with a cold trap or plan on rebuilding it, what is bp
of Br2 at 0.1 C?)). Main cut is pure S2Br2 at 46-48 C.
Hmmm as you may not condense out the Br2 even at liq N2 temperatures, you may have to set up a scrubber to protect your pump.
Sulfur remains in the pot.
[Edited on 6-5-2007 by Sauron]Maya - 7-5-2007 at 07:59
<<< Contrary to @Maya's post, sorry to say, there does not seem to be any such animal as SBr2 >>>
Actually, I made the assumption that Br chemistry is analogous to Cl chemistry. But you made the opposite assumption that the Br moeity does not
exist. Maybe at different temperatures and pressures it likely does; but people haven't tried those combinations yetEclectic - 7-5-2007 at 08:03
Maya, did you even read that article? The authors are using "S" to signify succinyl, NOT sulfur.
[Edited on 5-7-2007 by Eclectic]Sauron - 7-5-2007 at 08:38
@Maya, I made no assumptions. If I had assumed anything I would have assumed the same as you did. That Br2 sulfur chemistry mirrors Cl2 sulfur
chemistry. A reasonable assumption.
However, SBr2 appears to be absent from the literature. Not in Mellor, not in Brauer.
That is not an exhaustive search but it is strongly suggestive.
I don't have any ego invested in this issue; if it turns out that SBr2 exists and has been characterized, I will be pleased to stand corrected. It's
just that I did go look for it, and didn't find it so far. As someone else just shot your only reference down in flames, where's the beef?
I'll be happy to agree with you that there's no obvious reason I can see that SBr2 (Br-S-Br) "ought" not to exist, but by itself, that means nothing.
Pax!Maya - 7-5-2007 at 10:53
<<< Maya, did you even read that article? The authors are using "S" to signify succinyl, NOT sulfur. >>>
It was a joke!!!!!!!!!!!! Duh
@Sauron, agreed , hasn't been characterized. I haven't and won't invest the time to go to the chem section in library.
But, it may be because of an instability issue at room temp and room pressure.
and thats all that I have to say on this subjectstimo-roll - 31-8-2007 at 09:51
Can SBr2 be used for monobromination aromatic substanses like a p-diMeO-benzene?Sauron - 1-9-2007 at 01:15
It's a meaningless question since there is no apparent evidence that SBr2 has ever been prepared or characterized.
S2Br2 certainly has. That is Br-S-S-Br.
But Br-S-Br has not AFAIK.
It is quite possible that the heavier bromine atoms cannot long remain in this configuration.
There are plenty of similar examples. Carbonyl cyanide is much less stable than phosgene and carbonyl iodide even less so. The cyanogen halides follow
same pattern.
Perhaps computational chemistry software could shed some light on this.stimo-roll - 1-9-2007 at 03:03
but SCl2 exists. I wondering why in inorganic books no methods for prepation SBr2.Sauron - 1-9-2007 at 03:10
You can't always rely on analogy in these matters.
I also assumed SBr2 existed, until I tried to find it in the literature. I can't pretend to have done a completely exhaustive search, but I did get
deep enough in to decide with reasonable confidence that it's a no-go.
If anyone can prove me wrong by either preparing and characterising SBr2 or by finding it done in the (relatively) modern lit., say post 1900, I will
be happy to stand corrected.stimo-roll - 1-9-2007 at 09:34
you are right, this link fake me.http://www.chemteq.ru/lib/book/?book_idn=000117&page=102
something tell me that you also can read this.
[Edited on 1-9-2007 by stimo-roll]Sauron - 1-9-2007 at 19:42
Sorry, I don't read Cyrillic.not_important - 2-9-2007 at 00:11
The reference describes heating 4.8 grams of sulphur and 3.8 ml of bromine in a thick walled tube on a waterbath for 2 hours.
Inorganic Chemistry: By Arnold Frederick Holleman, Egon Wiberg (2001)
says formation of S2Br2 goes by way of the unstable SBr2
Thus the SBr2 of the first may be a mixture of SBr2, S2Br2, and Br2.Sauron - 2-9-2007 at 04:00
That's clear enough as a hypothesis. But this implies that SBr2 always disproportionates to S2Br2 + Br2. Easily tested and excess Br2 wasily removed,
and S2Br2 being stable, is purifiable. The mass balance can be verified.
Note that, while SCl2 and S2Cl2 can be obtained in pure form, that such disproportionation to a mixture is the norm afterwards, as well. This is of
importance in the preparation of CCl4, as the chlorination of CS2 initially produces a mixture of both sulfur chlorides plus trichloromethyl
mercaptan. Rupp and Meyer developed a technique for converting this tertiary mixture into a binary one by passing it through granular AC, to
facilitate the otherwise difficult fractionation. Subsequently, the pure sulfur chloride isolated slowly disproportionates back to a mixture but
another pass through the AC fixed bed, reverses that.
Would you care to see their writeups from Synthesis and the corresponding patents? Those fellows were with Akso and were mainly cncerned with a route
to thiophosgene.
Anyway, as I surmised, thesame sort of disproportionation takes place with sulfur bromides, but is apparently even more unfavorable to SBr2 so that
its isolation and characterization as a pure compound may have never been accomplished. Unlike S2Br2.
And if you look at S8 + I2 you will see that the situation is even murkier.Sauron - 4-9-2007 at 15:50
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.
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 helpsSauron - 4-9-2007 at 19:29
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-BrSauron - 5-9-2007 at 18:13
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.Sauron - 8-9-2007 at 23:02
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]garage chemist - 9-9-2007 at 09:50
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?Sauron - 9-9-2007 at 10:23
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.Cat_got_my_tungsten! - 23-9-2007 at 12:04
That is one hell of an experiment. Nice one woelen, nice one.
. I kept on adding sulphur, till no more dissolved.
And that is quite a lot, relative to the volume of bromine!