Dextrose-based momentum-sensitive mixture

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Discussion Overview

The discussion revolves around a laboratory experiment involving a dextrose-based mixture that exhibits color changes when shaken. Participants explore the chemical reactions occurring between dextrose, methylene blue, and other components, particularly focusing on redox reactions and the role of oxygen in the process.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant describes the initial experiment with KOH, water, dextrose, and methylene blue, noting the color change from blue to transparent upon shaking and back to blue after resting.
  • Another participant identifies dextrose as an aldehyde that is oxidized by methylene blue, which is reduced to leucomethylene blue, questioning what the oxidation product of dextrose is.
  • A different participant introduces the concept of gluconic acid and sodium gluconate, expressing confusion about their roles in the reaction and the relevance of oxygen.
  • One participant confirms that shaking the solution introduces oxygen, which facilitates the reactions by increasing its availability in the mixture.

Areas of Agreement / Disagreement

Participants express various hypotheses regarding the chemical processes involved, particularly concerning the oxidation of dextrose and the role of oxygen. There is no consensus on the specifics of the reactions or the exact products formed.

Contextual Notes

Participants mention the potential involvement of oxygen and the regeneration of methylene blue, but the details of these processes remain unclear. The discussion includes assumptions about the nature of the reactions and the compounds involved, which are not fully resolved.

Who May Find This Useful

This discussion may be of interest to those studying chemistry, particularly in the areas of redox reactions and the behavior of organic compounds in solution.

Weissritter
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O hai, PF
So, again, I come in the seek of help. I am usually good for my level on Chemistry, but this question was too hard for me.
In the lab, we added 0.8 g of KOH and 30 ml of H2O. Then, 1g of dextrose and methylene blue.
Final results were a liquid blue mixture. Thing is, when that thing is shaked, it changed to a transparent color. After resting, it became blue again. If shaked again, it would become transparent, then, after resting, blue again and ad infinitum.
Just why did this happen? What kind of reaction was happening?
As the final data I can give, the lab report says we could also have used glucose instead of dextrose. We were, also, studying redox reactions, I'd guess this one was redox, but what was it?

Was it K2O reacting to the dextrose? Was O2 changing its oxidation state by entering and leaving the compund depending on the momentum?
 
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The dextrose (glucose by another name) is an aldehyde that is oxidized by methylene blue. The methylene blue is reduced to leucomethylene blue (colorless) as it oxidizes the dextrose to ... what? The reaction stops there except you can do something to regenerate the methylene blue. What agent might be responsible for regenerating methylene blue from the colorless (actually light yellow, BTW) leucomethylene blue? How does shaking accelerate that reaction? Hint: it has nothing to do with momentum.
 
After some accidental searching, I found a name. Gluconic acid that can transform to sodium gluconate. I don't have the slightest idea of how those compounds are, but they do some weird magic.
No, no that kind of magic. I mean MAGIC, in capital and everything.
Now...what? I'm sure oxygen is part of the reaction, yet I'm clueless about how it is relevant.
 
You are right about oxygen - shaking the solution introduces the oxygen (which otherwise is present only close to the surface), allowing reactions to start.
 

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