bmays
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Help with bromine from bromate
I would like a small bit of bromine for a bromination. I will use the sodium bromate, potassium permanganate, and sulfuric acid method. Any ideas how
to do this without an addition funnel? Maybe substitute sodium sulfate in place of sulfuric acid and keep the reaction chilled?
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thesmug
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You probably won't be able to do this without some sort of slow-release mechanism, sorry. As far as I know this can be done with HCl so chilling
wouldn't be super necessary but I don't think sodium sulfate would work because these reactions typically need some sort of acid but I'm not entirely
sure.
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unionised
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Sodium bromate, potassium permanganate, and sulfuric acid will not produce bromine.
It is also likely to be dangerous to try it.
Do you mean sodium bromide?
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phlogiston
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If you really do have a bromate (which salt?) perhaps you should consider converting it to a bromide salt first and proceed from there.
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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eidolonicaurum
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I have a similar problem, and mix the reactants together in the reaction flask cold quite quickly, causing little bromine to be produced initially.
The mixture is then gently heated to distil the bromine off. Its riskier than using an addition funnel, and I have no idea how it affects yield, if at
all. But it works.
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chornedsnorkack
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Quote: Originally posted by unionised  | Sodium bromate, potassium permanganate, and sulfuric acid will not produce bromine.
It is also likely to be dangerous to try it.
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They do. It is just that potassium permanganate is unnecessary and adds a mess.
Bromic acid is unstable in concentrated solutions and decays. While bromine oxides exist, different routes are used to produce them - simple
acidification of bromates would give just bromine and oxygen. Thus total:
4NaBrO3+4H2SO4=4NaHSO4+2H2O+2Br2+5O2
So... what is a convenient H2SO4 concentration to perform that reaction quantitatively, rapidly and yet nonviolently and separate the resulting
bromine from the H2SO4/NaHSO4 solution?
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Metacelsus
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If you have bromate, you can react it with bromide and sulfuric acid:
BrO3- + 5 Br- + 6 H+ -> 3 Br2 + 6 H2O
This is a comproportionation instead of just a reduction.
[Edited on 7-4-2014 by Cheddite Cheese]
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woelen
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| Quote: Originally posted by phlogiston | | If you really do have a bromate (which salt?) perhaps you should consider converting it to a bromide salt first and proceed from there.
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That would be a horrible waste of chemicals. Much better is to reduce the bromate with bromide and add some
acid.
See Cheddite Cheese's answer!
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bmays
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I apologize for that, it is sodium bromide i have from the pool supply. I was looking at a jar of sodium bromate, i thought i just transferred it to
the jar but i now remember this was made in an electrocell.
I believe the reason behind permanganate was sulfur dioxide.
NaBr + H2SO4 = Na2SO4 + Br2 + H2O + SO2
Br2 + SO2 = HBr
KMnO4 + HBr = Br2
In the case of sodium bromate then the hydrosulfite formed will also eat the bromine i think.
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chornedsnorkack
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| Quote: Originally posted by bmays | I apologize for that, it is sodium bromide i have from the pool supply. I was looking at a jar of sodium bromate, i thought i just transferred it to
the jar but i now remember this was made in an electrocell.
I believe the reason behind permanganate was sulfur dioxide.
NaBr + H2SO4 = Na2SO4 + Br2 + H2O + SO2
Br2 + SO2 = HBr
KMnO4 + HBr = Br2
In the case of sodium bromate then the hydrosulfite formed will also eat the bromine i think. |
I think it wouldn´t.
SO2 would form hydrosulphite in a weakly acidic, very dilute or neutralized environment, because H2SO3 is a weak acid and separates as a gas. But in
these circumstances, sulphuric acid or sulphate are not oxidizing, and cannot be reduced even by metals that reduce hydrogen in dilute acid. Let alone
bromide! Bromide would be oxidized in concentrated sulphuric acid.
And there is a wide range of sulphuric acid concentrations where it should neither oxidize bromide nor allow sulphurous acid to form hydrosulphite.
But yes, it would be convenient to have another oxidant, like KMnO4. This would allow bromine to be oxidized over wider range of sulphuric acid
concentrations.
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