RadicallyStabilized
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Caution: Making bromine from TCCA and ammonium bromide does not work
I attempted to make some bromine using NileRed's method with TCCA and HCl (https://www.youtube.com/watch?v=eaIps1WxJPQ). I tried to do this with ammonium bromide instead of sodium bromide, and on a smaller scale (one
third, i. e. 24 g of TCCA).
A three-neck RBF was equipped with a distillation adapter, a glass stopcock and an addition funnel. I charged it with the powdered TCCA and then added
the prepared aqueous ammonium bromide solution through an ordinary glass funnel on the distillation adapter. When I had added only about 10 ml of the
solution there was a sudden very strong evolution of bromine gas, and then - BAM! - the stopcock was blown off and shattered. The funnels were also
ejected but fortunately remained intact. As I did this in the fume hood the damage was easily contained. But the explosion noise was definitely
impressive.
In NileRed's video (using NaBr) there is only a slight evolution of bromine and no build-up of pressure. Does anybody know why ammonium bromide
behaves so differently?
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barbs09
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Sounds like the reaction pathway was spot on, just the rate that was problematic!! Same concentration of bromide solution? Same temperature? Did the
originator grid the TCCA finely?
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beta4
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When I bought NaDCC I did a little search to assess its safety, and found the MSDS listing "nitrogen containing materials" as incompatible.
I also found this old thread: http://www.sciencemadness.org/talk/viewthread.php?tid=5686
Quote: Originally posted by praseodym  | | Nitrogen trichloride may from if TCCA contacts ammonia, ammonia salts, urea, or similar nitrogen - containing compounds. |
So you may have inadvertently made a small amount of nitrogen trichloride.
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Okrutnik2137
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Perhaps the rate was too quick, besides bromine probably reacted with ammonia in an exothermic manner this sped up both reaction and BAM!
As beta4 mentioned you've probably made small amounts of nitrogen tribromide.
[Edited on 30-8-2020 by Okrutnik2137]
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UC235
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https://woelen.homescience.net/science/chem/exps/raw_materia...
Scroll down a bit. TCCA reacts with ammonia to nitrogen gas. You can convert your NH4Br to NaBr by boiling with NaOH until NH3 ceases coming off of
the solution if you don't have another source of bromine.
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RadicallyStabilized
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Yes, I think that's very likely. The reaction was very sudden, more like a detonation than an exothermic pressure buildup.
I thought I was safe because I used ammonium ion, not ammonia... but apparently I should have researched a bit more. You never stop learning,
sometimes the hard way...
Thanks for all the replies!
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beta4
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After having a look at this link, however, I'm curious why nitrogen trichloride wasn't produced in this experiment. Maybe the reaction conditions such
as the low ammonia concentration favor the direct decomposition of the reagents to nitrogen gas.
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Tsjerk
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Woelen has a page about bromine oxidation of ammonia, but he states ammonium is not oxidized. Also TCCA is pretty acidic so all ammonium will be
protonated.
link
[Edited on 30-8-2020 by Tsjerk]
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symboom
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I would have definitely thought nitrogen Trichloride is produced the TCCA releases chlorine and chlorine reacts with ammonium salts such as ammonium
sulfate, chloride, and nitrate it should do the same with ammonium bromide forming nitrogen trichloride and hydrochloric acid which will react with
ammonium bromide forming ammonium chloride and hydrogen bromide which then is oxidized by chlorine to bromine and HCl. The other pathway is ammonium
bromide is converted to ammonium chloride and bromine.
[Edited on 30-8-2020 by symboom]
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woelen
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TCCA and ammonia (in any form, including ammonium ion) is a dangerous combination. The same is true of the combination of Cl2 and ammonia (or ammonium
ion). Bromine reacts with ammonia, but not with ammonium ion. Actually, pouring bromine in aqueous ammonia is a viable method of making ammonium
bromide in the lab. Making ammonium chloride form ammonia and chlorine in a similar way would be foolish, due to the risk of formation of NCl3 and
possible explosion.
I think that in your experiment indeed Br2 is formed, but there also was a side reaction, which led to a very violent reaction.
Just for fun, if you have concentrated ammonia (e.g. 15% or better), add a pea-sized chunk of TCCA to a few ml of the ammonia. Do NOT use larger
amounts! Be impressed!
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RadicallyStabilized
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Just a short addendum how I disposed of the unreacted TCCA. It is an oxidant, harmful for aquatic organisms and generates chlorine when wet, so it's
not something I wanted to keep, pour down the drain or dump into the trash.
As mentioned here: https://www.sciencemadness.org/whisper/viewthread.php?tid=56...
TCCA can be reduced with a bisulfite salt (HSO3-). Some water was added to the remaining TCCA and an excess of a sodium metabisulfite (Na2S2O5)
solution was added and stirred for 15 minutes. Potassium metabisulfite could also be used but is not as readily soluble. This can release SO2 in
unpleasant amounts, so provide ventilation. The reaction itself is not exothermic to a significant degree.
To test for unreacted TCCA a few crystals of potassium iodide can be dissolved in water. A few drops of the (presumed) TCCA solution are then added.
If the solution turns yellow (iodine is released) it indicates TCCA still being present.
The reaction product was vacuum filtered and dried. It consists of cyanuric acid which is "essentially nontoxic" (Wikipedia) and can be kept or thrown
away. The filtrate contains relatively harmless salts, a small amount of cyanuric acid and dissolved SO2. It should be safe to pour down the drain.
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AJKOER
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My understanding of the chemistry is that the •HO2 radical is key to liberating the Br2. As such, my recommended chemistry would be to dilute the
NH4Br first with H2O2. Then, carefully add a very small amounts of your TCCA, a source of HOCl, to the solution, expecting much bubbling/frothing.
Logic: H2O2 + HOCl is a source of transient hydroxyl radical (•OH) (see https://ucdavis.pure.elsevier.com/en/publications/hydroxyl-r...) and even Singlet Oxygen (O(1P)). The latter reacts with water also creating yet
more hydroxyl radicals. In the presence of H2O2:
H2O2 + •OH -> H2O + •HO2
which is the key radical (which exists at pH < 4.88 and when the superoxide radical anion, •O2-, is in the gas phase in the present of water
vapor). Source: See this work noting free bromine formation (and not complexed), 'Hydroperoxyl radical (•HO2) oxidizes dibromide radical anion
(•Br2−) to bromine (Br2) in aqueous solution: Implications for the formation of Br2 in the marine boundary layer', a work by Brendan M. Matthew,
et al, fully available (for free) at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... .
Note: First, Singlet oxygen is toxic but have a limited half-life. The H2O2 should be in relative excess to your HOCl source. Basically, I have
changed from active chlorine chemistry to largely oxygen based species, and so, on the action of •HO2 on NH3/NH4+, for example, expect N2, NO3-,
NO2-,..., products.
Do test for safety in small amounts given the expected vigorous nature of the reaction.
[Edited on 5-9-2020 by AJKOER]
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unionised
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| Quote: Originally posted by AJKOER | My understanding of the chemistry is that the •HO2 radical is key to liberating the Br2. As such, my recommended chemistry would be to dilute the
NH4Br first with H2O2. Then, carefully add a very small amounts of your TCCA, a source of HOCl, to the solution, expecting much bubbling/frothing.
Logic: H2O2 + HOCl is a source of transient hydroxyl radical (•OH) and even Singlet Oxygen (O(1P)). The latter reacts with water also creating yet
more hydroxyl radicals. In the presence of H2O2:
H2O2 + •OH -> H2O + •HO2
which is the key radical (which exists at pH < 4.88 and when the superoxide radical anion, •O2-, is in the gas phase in the present of water
vapor). Source: See this work noting free bromine formation (and not complexed), 'Hydroperoxyl radical (•HO2) oxidizes dibromide radical anion
(•Br2−) to bromine (Br2) in aqueous solution: Implications for the formation of Br2 in the marine boundary layer', a work by Brendan M. Matthew,
et al, fully available (for free) at: https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/200... .
Note: First, Singlet oxygen is toxic but have a limited half-life. The H2O2 should be in relative excess to your HOCl source. Basically, I have
changed from active chlorine chemistry to largely oxygen based species, and so, on the action of •HO2 on NH3/NH4+, for example, expect N2, NO3-,
NO2-,..., products.
Do test for safety in small amounts given the expected vigorous nature of the reaction.
[Edited on 5-9-2020 by AJKOER] |
Why did you post that?
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AJKOER
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Thanks Unionised:
On your question: "Why did you post that?", actually, three answers, first based on the prior comment above by Woelen:
| Quote: Originally posted by woelen | TCCA and ammonia (in any form, including ammonium ion) is a dangerous combination. The same is true of the combination of Cl2 and ammonia (or ammonium
ion). Bromine reacts with ammonia, but not with ammonium ion. Actually, pouring bromine in aqueous ammonia is a viable method of making ammonium
bromide in the lab. Making ammonium chloride form ammonia and chlorine in a similar way would be foolish, due to the risk of formation of NCl3 and
possible explosion.
I think that in your experiment indeed Br2 is formed, but there also was a side reaction, which led to a very violent reaction....
|
which is an apparently negative characterization of the cited reaction path.
Second, I have reported my personal experience on trying to attack (NH4)2SO4 with HOCl on this very forum (see https://www.sciencemadness.org/whisper/viewthread.php?tid=28... ), where that negative experience affirms Woelen's assessment.
Third, my understanding of the reaction mechanics as documented (good practice), suggests a seemingly small addition (H2O2) to the procedure to
ostensibly transform it from Woelen depiction's into a more safe and possibly effective path (based on cited science) for bromine (uncomplexed)
liberation.
Of course, you are free to embrace the original protocol to its fullest extent.
[Edited on 5-9-2020 by AJKOER]
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