tekkado
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Reaction Kinetics
Hi all,
just in need of some help at the moment. I will be running a reaction oxidising borneol to camphor using sodium hypochlorite and acetic acid. I need
to monitor the progress of this reaction to determine the activation energy. since there wont be time to sample it on uv-vis im struggling to think of
a way to monitor it.
there is no appreciable temperature change or in pH, and no colour change.
I was thinking of using a volt meter immersed in the reaction up to its completion and plotting voltage over time to calculate but i cant seem to find
any info on how to go about this.
If anyone could point me in the right direction that would be greatly appreciated.
thanks
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Metacelsus
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Take a sample every few minutes and quench it (using any mild reducing agent), then run the samples. GC would be good if you have it. I don't think
borneol or camphor would absorb much UV, but you could give UV-vis a try.
If you're determining activation energy, you need to be able to control the temperature precisely.
Edit: you might also be able to do an iodimetric titration after quenching to determine how much hypochlorite was remaining at each time. But this
would require more material.
[Edited on 2019-5-16 by Metacelsus]
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CharlieA
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Are you "biting off more than you can chew"?
I can offer only a general method; the specific implementation of the method will be up to you.
Assuming that the reaction is not super fast, you could take aliquots of the reaction mix at various times into the reaction. As each aliquot is
taken, it is "quenched" in some way that will stop the reaction quickly. Than the quenched sample is analyzed for the amount of reactant remaining,
or for the amount of product formed.
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CharlieA
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@Metacelsus: "Great minds travel the same paths!" 
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Pumukli
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My first thought was "iodometry for hypochlorite". But I remember running a very similar reaction (menthol to menthone) which started as a homogenous
mixture but after I added about 10% hypochlorite the mixture became opaque and oil droplets separated. This might have been avoided if I had used a
lot more acetic acid as solvent, but I'm not 100% sure.
A GC analysis seems more promising. I don't think the column would like having samples injected straight from the mixture so an extraction step may be
required. If you add the hypochlorite slowly, drop by drop, then quenching may not be required as the reaction is quite fast. (It was in the menthol
case.)
Edit: I see you need kinetic data, so you have to mix the reagents at once, not drop by drop...
[Edited on 16-5-2019 by Pumukli]
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