angelhair
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Getting rid of Bromine
I have about 1 liter of bromine that has become a liability to have around because it leaks through everything, so I want to either get rid of it
responsibly or turn it into something easily that I can store safely, other than N-Bromosuccinimide because I don't know where to get the succinimide.
What do you think?
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chloric1
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Real simple,
Do you have any bromides?
You can slowly drip bromine into cold strong KBr and add strong ammonia VERY carefully until ammonia smell Barely persist and solution is colorless.
Or add the bromine VERY CAREFULLY to the ammonia to get pure ammonium bromide.
Or drip into cold concentrated sodium metabisulfite solution. I like reducing with ammonia myself. You get ammonium bromide. Ammonia is oxidized
to nitrogen so no impurities should be present in your ammonium bromide.
Fellow molecular manipulator
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not_important
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Seal it into glass ampules, as many here have done.
React it with sodium carbonate to get a mixture of soium bromide and bromate
3Br2 + 3 Na2CO3 => 5 NaBr + NaBrO3 + 3 CO2
The solution of the mixed salts can be evaporated to get a dry solid, there should be a slight excess of Na2CO3.
Acidifying a solution of the mixed bromide+bromate regenerates bromine
5 NaBr + NaBrO3 +3 H2SO4 => 3 Na2SO4 + 3 Br2 + 3 H2O
React it with scrap iron to get ferrous bromide, which can be converted into sodium or potassium bromides by reacting the FeBr2 with the carbonate.
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DJF90
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Ampouling a liter of bromine sounds like a bit of a task...
Reaction with cold sodium hydroxide solution yields sodium bromide and sodium bromate (I) (a.k.a. sodium hypobromite).
Reaction with hot sodium hydroxide solution yields sodium bromide and sodium bromate (V).
Reaction with sodium thiosulphate solution yeilds sodium bromide and sodium tetrathionate (Na2S4O6).
Make a solution of bromine in a non polar solvent (hexane maybe?) and use as you would bromine itself (for most things anyway). Note that this
solution should probably be stored in an amber bottle or in a dark place to prevent free radical substitution.
If phosphorus is available then phosphorus tri/penta bromide would be useful for bromination reactions such as synthesis of alkyl bromides or acyl
bromides and a multitude of other compounds.
Reaction with benzene in the presence of an iron catalyst yields bromobenzene.
Reaction with phenols require no catalyst and yields multiple substitution products (for example with phenol 2,4,6-tribromophenol is produced).
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unionised
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Chloric1
How would you produce nitrogen tribromide?
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woelen
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Where is chloric1 talking about nitrogen tribromide? He mentions ammonium bromide, and indeed, that is the reaction which occurs. I know of this
procedure and tried it myself. It works like a charm, but it is VERY exothermic.
What happens is the following: 8NH3 + 3Br2 --> N2 + 6NH4Br (+ a lot of heat)
The intermediate steps go through HBr, which immediately forms NH4Br with excess ammonia. This reaction is very clean. If your starting product is
pure Br2 and you have clean ammonia, then you get a very pure solution of NH4Br (in possibly excess NH3). Heating simply drives off water and NH3 and
you are left with pure NH4Br.
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sparkgap
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I think unionised was asking, in his usual oblique way, if the procedure runs the risk of producing nitrogen tribromide. I can vouch for the cleanness
(and exothermicity!) of making ammonium bromide, and that it won't make nitrogen tribromide under the usual conditions.
sparky (~_~)
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unionised
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The possible formation of "NBr3" was, indeed, what I was refering to.
IIRC you need an excess of Br2 in order to convert the NH4Br produced initially.
Would someone like to work out how big a bucket of ammonia solution you would need to cope safey with a litre of Br2?
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angelhair
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I like the sound of ammonium bromide and sodium bromide/ate. Is the reaction with Sodium carbonate very exothermic?
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woelen
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Neutralizing 1 liter of bromine would require appr. 4 liter of 25% ammonia. In order to have some excess ammonia, I would go for 4.5 liters of 25%
ammonia.
NBr3 is not formed, not under any condition. If an excess amount of Br2 is used, then it remains in solution, unreacted, besides already formed NH4Br.
Ammonium ion and bromine do not react like ammonium ion and chlorine. The analogy does not hold here.
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DJF90
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Strange how the analogous reaction does happen with iodine though. I wonder why chlorine and iodine both form nitrogen trihalides with ammonia but
bromine can't...
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not_important
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| Quote: | Originally posted by angelhair
Is the reaction with Sodium carbonate very exothermic? |
Not terribly on the scale I've done it, which wasn't very large and more targeted at recovering escaping bromine. But is is, or was, used
industrially to capture bromine, often from a stream of Br2+H2O+inert gas, and then regenerate the Br2 by acidifying the mixed bromide-bromate after
concentrating the solution.
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angelhair
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Where can I read about these proceedures? Is it in Inorganic chemistry text books, or publications like Faith, Keys and Martin?. I only have Organic
text books.
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woelen
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| Quote: | Originally posted by DJF90
Strange how the analogous reaction does happen with iodine though. I wonder why chlorine and iodine both form nitrogen trihalides with ammonia but
bromine can't... |
The reactions with chlorine and iodine by no means are analogous. Clorine gives NCl3 with ammonium ion, not with ammonia. Formation of NCl3 does not
occur in alkaline environments. It must be on the acidic side of the pH scale.
The compound "NI3", which is formed with ammonia (not ammonium) and iodine also has a VERY different structure, compared with NCl3. NCl3 is a covalent
molecule, "NI3" is not a simple molecular species but some macromolecule, which also has ammonia molecules entrapped. The empirical formula is not
NI3, but NI3.nNH3, where n depends on method of preparation, concentration, temperature. The precise structure of "NI3" is amazingly complex, and IIRC
it still is only partially understood.
So, when looked at at first glance, there may seem to be an analogy between iodine and chlorine in this kind of reactions. In reality there is none,
not at all.
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Formatik
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According to Gmelin's Handbook of Inorganic Chemistry, Br [B2] p. 199, aqueous ammonium salt solutions and bromine react to form NBr3, where the NBr3
is obtained by bromination of NH3 through HBrO (which forms by reaction of bromine with water) as follows:
HBrO + NH3 <-> H2O + NH2Br
HBrO + NH2Br <-> H2O + NHBr2
HBrO + NHBr2 <-> H2O + NBr3
They state NBr3 forms when the mole ratio of the salts is around 2 Br2:3 NH3 and the pH is less than 8. The red-violet NBr3 is very dangerous as it
can explode at the slightest disturbance in a Nujol-pentane suspension at even -100 ºC.
But NBr3 decomposes exothermically from aqueous NH3 and in the process gives the dense white fumes, any NBr3 that would be formed decomposes from the
ammonia (if it can form from excess bromine and a small of amount aqueous ammonia to offset the pH), that being the case I would think to add bromine
to ammonia and not vice versa.
[Edited on 25-4-2008 by Schockwave]
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VTchem
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Just out of curiosity, where did you get a liter of Bromine? I read all the stuff (or at least I think I did) about chemical procurement but I don't
remember bromine being on the list.
You should be able to add it to any alkene if you don't want to use the NH3 solution. Just be careful and what ever you do, do it slowly, bromine is
mean stuff.
Go Hokies! \"If it goes \'BOOM\' I like it!\" -Me
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Jdurg
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| Quote: | | bromine is mean stuff. |
Heh. That's putting it mildly! The stuff does a great job of seeping into everything an anything you have around it. Be very careful that you don't
spill it. That can result in a nasty mess.
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
http://maddox.xmission.com. |
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Jdurg
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| Quote: | Originally posted by woelen
| Quote: | Originally posted by DJF90
Strange how the analogous reaction does happen with iodine though. I wonder why chlorine and iodine both form nitrogen trihalides with ammonia but
bromine can't... |
The reactions with chlorine and iodine by no means are analogous. Clorine gives NCl3 with ammonium ion, not with ammonia. Formation of NCl3 does not
occur in alkaline environments. It must be on the acidic side of the pH scale.
The compound "NI3", which is formed with ammonia (not ammonium) and iodine also has a VERY different structure, compared with NCl3. NCl3 is a covalent
molecule, "NI3" is not a simple molecular species but some macromolecule, which also has ammonia molecules entrapped. The empirical formula is not
NI3, but NI3.nNH3, where n depends on method of preparation, concentration, temperature. The precise structure of "NI3" is amazingly complex, and IIRC
it still is only partially understood.
So, when looked at at first glance, there may seem to be an analogy between iodine and chlorine in this kind of reactions. In reality there is none,
not at all. |
Actually, I believe the structure of NI3 proper is known as it has been produced under fairly strict conditions from a boron nitride and HI if memory
serves me right. It can be found by doing a quick google search.
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
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not_important
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| Quote: | Originally posted by VTchem
...
You should be able to add it to any alkene if you don't want to use the NH3 solution... |
A rather expensive way to 'get rid' of the bromine, plus it makes halocarbons which usually have regulations regard their release and disposal, and
many of which are toxic.
If you don't go the NH route, use the carbonate; cheap, effective, lets you store and recover elemental bromine when you want it. If you heat the
mixed bromide+bromate to red heat, the bromate decomposes to bromide; a way to get just NaBr.
If you do the carbonate roue, keep it cool to cold, add the bromine slowly, for a better yield of the mixed Br/BrO3. Higher temperatures lead to
bromide in stead of bromate.
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Jdurg
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If you want a massively useless, yet amazing, reaction, just throw a bunch of aluminum metal in there.
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
http://maddox.xmission.com. |
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