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El.Sorbos
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In my second experiment strong cooling with water salt/ice solution was applied, so temperatures didn't rose over 10 degree. Also stirring was strong
enough, so no hot spots are noticeable. (mechanical stirring)
Your filter cake extract was also black, so i come to the thesis the solvent are react with the dichlorocynuricacid?
I think one of my errors was my extraction technique, because i worked sloppy. In my next try i will perform additional a slower addition of my
NaDCCA, maybe i underestimated the reaction kinetic and you a right with the temperature argument. 
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JJay
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When I was sorting through some old research recently, I ran across a paper saying that monochlorinated amino acids degrade irreversibly in the
presence of base to form aldehydes, while dichlorinated amino acids degrade to form nitriles.
If aldehydes are forming, that can hurt yields in at least a couple of ways - by using up the amino acid to produce side products - and by unwanted
chlorination of the product by unconsumed chlorine. I'm not sure how fast the degradation into an aldehyde is, but I'm pretty sure that water can
serve as the base, especially if the temperature is high enough. I guess that is why amino acid to aldehyde syntheses with TCCA or hypochlorite tend
to use such dilute conditions. I'll see if I can find the paper....
[Edited on 20-7-2018 by JJay]
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AvBaeyer
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JJay,
What you have mentioned is actually quite important for the success of the procedure I posted. The reaction I described uses the sodium salt of
phenylalanine and an aqueous solution of NaDCC. As a result, the pH of the reaction is always near neutrality which inhibits the formation of the
aldehyde product. Thus, N-dichlorination becomes the predominant pathway with subsequent formation of the nitrile as a slow step. As I have also
pointed out, careful temperature control is extremely important to inhibit the formation of dark colored by-products. I believe the good points you
have raised are covered in some of the references I cited.
AvB
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JJay
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Yep, quite likely. You really did some amazing work on this, BTW.
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Loptr
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I found another paper regarding the bromodecarboxylation of alpha-amino acids that I haven't seen before. It discusses some of the reactions that take
place when using NBS that can lead to the expected nitrile, a nitrile of one less carbon, or an aldehyde.
Attachment: J. Biol. Chem.-1961-Stevenson-715-7.pdf (382kB)
This file has been downloaded 652 times
"Question everything generally thought to be obvious." - Dieter Rams
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John paul III
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What the puropse of washing the organic solution with K2CO3 and brine?
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thioacetone
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Hi just wondering a few things - if anyone can please help:
- Can I use diethyl ether instead of DCM?
- I don't have access to iodine/iodides for the starch test - is there any way to avoid it?
- Can I use sodium metabisulfite instead of bisulfite?
- Can I dry with anhydrous magnesium sulfate instead of sodium sulfate?
Thanks
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