Sulaiman
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Briggs–Rauscher reaction - Chemical Oscillations
The Briggs–Rauscher reaction interests me,
https://www.youtube.com/watch?v=WpBwlSn1XPQ
https://en.wikipedia.org/wiki/Briggs%E2%80%93Rauscher_reacti...
but malonic acid is required
e.g. https://projects.ncsu.edu/project/chemistrydemos/Kinetics/Br...
which I do not want to buy.
Oxalic acid is similar to Malonic and gets some mention
but I could not find recipies for oxalic acid converted to, or substituted for, malonic acid.
Am I wasting time looking for one, or just poor google-fu ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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pantone159
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I am pretty sure that you need malonic acid, I have never seen any substitutes for it in this reaction (or the BZ oscillating reaction either.)
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Sulaiman
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OK, thanks.
At least one to strike off a never decreasing list 
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CuReUS
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the wiki page clearly explains why malonic acid is used and also gives alternatives.But why don't you just use Sodium
metabisulfite(Na2S2O5) or sodium bisulfite(NaHSO3) instead of an organic compound ?
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careysub
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The original observation of oscillating chemical reactions by Belousov was in a system that had citric acid as its substrate, switching to malonic
acid greatly increased its amplitude.
Other substrates can be used, Briggs and Rauscher in their publication in the Journal of Chemical education states that they had also used
2,4-pentanedione (acetylacetone), and acetone itself has also been reported.
But malonic acid appears to be the optimized substrate for most purposes. Methylmalonic acid is similar, but the reaction is much slower, which can
be convenient for a public demonstration not confined to a single lecture session.
If you want to make malonic acid 2,4-pentanediol is available cheaply from MakingCosmetics (this fact, and a procedure for doing the conversion were
both reported by Magpie on this site). Elemental Scientific has malonic acid.
[Edited on 18-11-2016 by careysub]
Attachment: briggs1973.pdf (966kB)
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Attachment: Oscillating Reactions.pdf (67kB)
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About that which we cannot speak, we must remain silent.
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Some things can never be spoken
Some things cannot be pronounced
That word does not exist in any language
It will never be uttered by a human mouth
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j_sum1
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I can confirm that OA does not work. I found that out the hard way.
[edit]
And by the hard way, I mean this. A student of mine once undertook a project on using the BR reaction as a quantitative method for determining the
antioxidant content of fruit. The basic idea was: the period of the BR reaction depends on the concentration of oxidisers. Addition of vitamin C
slows the reaction down and therefore reduces the period of the oscillations. Mixing up some standard solutions would allow a calibration curve to be
constructed and therefore give a tool for analysing fruit juices etc. It has been done before. Her ideas looked good and I instructed her to go for
it.
At the time I was not that familiar with the Briggs Rauscher reaction and directed her to use oxalic acid since we had no malonic. I figured that
with the same functional groupings it would substitute ok. I was wrong. The poor kid spent a lot of time tweaking the recipe of a reaction that was
not going to work. She did however find a reference to acetone being able to perform the same function. She did not achieve success with this
either. But it did do something -- the solution changed colour over a 24 hour period.
Cool project. Pity we didn't have the MA to pull it off.
[Edited on 18-11-2016 by j_sum1]
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Sulaiman
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Thanks to YouTube videos, several by SM members, my interest in the Briggs–Rauscher reaction is, for now, sattisfied.
If I ever buy or synthesise malonic acid for some other reason then I'll have a go.
Thanks to everyone above.
CAUTION : Hobby Chemist, not Professional or even Amateur
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