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Author: Subject: Bleach and Haematoxylin (Logwood)
The Volatile Chemist
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[*] posted on 16-4-2014 at 12:35
Bleach and Haematoxylin (Logwood)


Well, I tried one of my first experiments in organic chemistry. In reality, it wasn't an experiment (Please don't criticize my non-experimental form of fun), but an assumption of a reaction I wanted to test.

I was rather certain that a reaction would occur between Haematoxylin (Haematien when it complexes, also known as logwood: http://en.wikipedia.org/wiki/Haematoxylin) and Bleach. My assumption was that the chlorine would dump it's sole oxygen someplace in the Haematoxylin structure (Speaking of the structure, see it on the Wikipedia page, it's a rather simple molecule), and make salt as a side product.

When I mixed a small amount of Haematoxylin dissolved in water (A hard to describe, violet blue purple color) with bleach, it turned a very light, very clear yellow. The yellow faded to clear eventually (Maybe it was just lighting), so it could have been coloration of the bleach. It still smelled bleach-y, so it could just be a complex or something, though I doubt it. I recommend reading the Wikipedia article if you have any questions about the odder of the two reactants.




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[*] posted on 16-4-2014 at 15:27


Well, I did the reaction again. The yellow color is not from excess haematoxylin, it appears to be an initial product. This seems to decay over time, and the solution becomes completely clear.



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EdMeese
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[*] posted on 3-6-2014 at 21:49


http://en.wikipedia.org/wiki/Haematoxylin

mostly see "...haematein, a product of oxidation of haematoxylin..."

bleach is an oxidizing agent, this is the place to start. A day in the library is worth a week in the lab.
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[*] posted on 4-6-2014 at 07:37


Quote: Originally posted by EdMeese  
http://en.wikipedia.org/wiki/Haematoxylin

mostly see "...haematein, a product of oxidation of haematoxylin..."

bleach is an oxidizing agent, this is the place to start. A day in the library is worth a week in the lab.

I wouldn't say it's worth that much. I don't have a great local library. But I did see this, and theorize that's what happened, after I posted this. Thanks for the input, though!




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smaerd
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[*] posted on 4-6-2014 at 09:32


I'm always skeptical about selective oxidations of organic substrates with things like NaOCl without further analysis as anyone probably should be. Never know though I guess.

Could always quench the bleach with a reducing agent. Perhaps thiosulfite. Or do an extraction although it appears like that may be difficult. Anyways the wikipedia for Hematein(the supposed product) says
Quote:
In acidic solutions, complexes of hematein with metals (usually aluminium or iron, but also chromium, zirconium and several others) are used as biological stains.


So there should be a way to at least do small test-tube scale tests to see if the color matches with the metal complexes. After comparison with the original material. Of course color eyeballing is not a qualitative technique but, it could let you know if it's worth investigating more thoroughly.

Interesting reaction though.




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[*] posted on 4-6-2014 at 09:35


Bleach sometimes can chlorinate, too, but there are a surprising number of selective oxidations with the stuff. Gotta have it in the lab ;-)
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