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woelen
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Bromine + sulphur
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]
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nitro-genes
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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]
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Maya
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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]
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woelen
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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.
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S.C. Wack
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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.
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Sauron
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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.
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not_important
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Mellor's says that "sulfur monobromide" can be made by dissolving sulfur in bromine, just STP, and that it resembles the chloride.
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Sauron
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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.
[Edited on 4-5-2007 by Sauron]
Attachment: Pages from brauer_ocr.pdf (148kB)
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DrP
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How easy is it to liberate the bromine from your red solution woelen?
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Maya
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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
\"Prefiero ser yo extranjero en otras patrias, a serlo en la mia\"
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woelen
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| 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.
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Eclectic
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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?
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Sauron
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@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]
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Maya
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<<< Contrary to @Maya's post, sorry to say, there does not seem to be any such animal as SBr2 >>>
Well then you just didn't look hard enough :-)
http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/1993/115/i09...
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 yet
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Eclectic
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Maya, did you even read that article? The authors are using "S" to signify succinyl, NOT sulfur.
Sufur Halides
[Edited on 5-7-2007 by Eclectic]
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Sauron
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@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!
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Maya
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<<< 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 subject
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stimo-roll
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Can SBr2 be used for monobromination aromatic substanses like a p-diMeO-benzene?
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Sauron
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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.
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stimo-roll
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but SCl2 exists. I wondering why in inorganic books no methods for prepation SBr2.
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Sauron
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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.
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stimo-roll
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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]
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Sauron
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Sorry, I don't read Cyrillic.
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not_important
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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
http://books.google.com/books?id=LxhQPdMRfVIC&pg=PA529&a...
Thus the SBr2 of the first may be a mixture of SBr2, S2Br2, and Br2.
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Sauron
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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.
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