C. Runge
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Research question - reduced pyridoxylamino acids and Hello.
Hello! I have been a lurker for some time now and have decided to finally make an account and join some discussions.
I guess to get the the point, I am an (almost) third year undergraduate chemistry student doing research for the first time. The project involves
determining crystal structures of reduced pyridoxylamino acids. After following the procedure for the creation of the compounds detailed by Heyl et
al. (https://pubs.acs.org/doi/abs/10.1021/ja01190a061) and Miyoshe Ikawa (sorry, not open access, and I only have paper copy) I have run into some
problems.
My compounds do turn a bright yellow color upon addition and stirring of pyridoxal HCl but even after hydrogenating for four hours the solution does
not lose its color as previously reported. I assume that the hydrogenation had failed. Each time the pressure in the container decreases as time
goes on. I first hoped that it was just that the hydrogen was being taken up by the solution. But dramatic changes from 40psi to 10psi in under an
hour makes me skeptical of that. I checked for H2 leaks on all fittings with soapy water (like one would check a tire for leaks) and did not find any
leaks. I also changed from a 5% palladium on carbon catalyst, to the more expensive platinum oxide catalyst used in the papers to no effect. The IR
spectra from before and after hydrogenation is also almost identical. Any ideas? The hydrogenation apparatus being used is a parr 3900 if any have
experience with it.
Sorry for the very long first post. Thanks very much, and I look forward to future forum participation  .
[edit] Title clarification
[Edited on 8-6-2018 by j_sum1]
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j_sum1
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Hello and welcome to SM.
I am sure you will find some interesting reading here if you stick around. And probably some people who can help with your questions. There are
quite a few bright sparks here. (I am not one of them.)
I have changed the title of your thread to better reflect what you are asking for. You should get a better response that way.
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Corrosive Joeseph
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Thank you j...........
@OP - Be welcome. Here is your paper for download so others can better help you.
'The Chemistry of Vitamin B6. VI. Pyridoxylamino Acids1
Dorothea Heyl, Stanton A. Harris, and Karl Folkers
J. Am. Chem. Soc., 1948, 70 (10), pp 3429–3431
DOI: 10.1021/ja01190a061
Publication Date: October 1948'
/CJ
Attachment: The Chemistry of Vitamin B6. VI. Pyridoxylamino Acids.pdf (439kB)
This file has been downloaded 331 times
Being well adjusted to a sick society is no measure of one's mental health
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DubaiAmateurRocketry
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Welcome here, its a great community
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C. Runge
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Thanks for the warm welcome and thread title change. Thanks also for grabbing that paper.
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zed
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Ummm. Hydrogenating a pyridine/piperidine type material with a Platinum catalyst.
Something in the mix, could be poisoning your catalyst.
The Amino Acids of today, are not the Amino Acids of yesteryear. Probably produced very differently. Same goes for everything else. When something
in the mix is poisoning your catalyst or activating it, it doesn't take much.
It's just a Shiff's base/imine, that you are trying to reduce?
Maybe Sodium Borohydride/ or Sodium Cyanoborohydride, would be more effective.
The 3900 shaker, and its descendants are kind of like fossils, though to be fair, the design has been a standard for a hundred years or so.. And,
it works.
https://www.labx.com/item/lab-equipment-parr-instrument-co-s...
Stirring is generally more effective, especially if you are using a very active "Brown" type catalyst; formed by the action of NaBH4 on Chloroplatinic
Acid.
Brown published a series of papers on his machines and his methods, and they are interesting reading.
This of course, might be no use to you, if some mystery contaminant is poisoning all Noble metal catalysts anyway.
[Edited on 9-6-2018 by zed]
[Edited on 9-6-2018 by zed]
[Edited on 9-6-2018 by zed]
[Edited on 9-6-2018 by zed]
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C. Runge
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Thanks for getting back with me. I have to admit, both the hydrogenation apparatus and the amino acids I am using are somewhat old (not sure on the
date, but my lab manager said that all chemicals were required to have a zip code on the label after 1962, and none of these glass bottles do haha).
Last summer a student was tasked with doing the same research as myself, and attempted to do so with sodium borohydride (as Billman and Diesing wrote
a paper detailing the reduction of schiff bases with the reagent) with no success as well. They eventually gave up, and I was given it this year and
told to reduce it differently.
The lab's HPLC just got serviced, so hopefully I might be able to better analyze the solution to see if maybe some of the sample was reduced, but the
presence of the unreduced sample is causing the yellow color to stay...
Thanks again for the input, I will definitely read the papers about the Brown catalyst.
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zed
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Me? I'd buy some fresh reagents, and make a fresh start.
Current state of purity of your reagents is questionable. 50 to 60 years, is a long time, and catalytic hydrogenation catalysts can be fussy.
In the 60s, vitamins and amino-acids might have been expensive. Quite expensive... And further, not readily available in bulk powdered form.
Now, on the health/vitamin/supplement market, such items are available at reasonable prices, with quick delivery times.
https://www.ebay.com/itm/Bulk-Supplements-Pyridoxine-HCL-Pow...
Go to your own pockets for the cash, if you must. As always, time is of the essence. Carpe Diem, etc....
Likewise, freshly prepared Nobel metal catalysts, are the most active. I have little faith is pre-prepared catalysts from a bottle.
Using enough catalyst for the job at hand, is important too. Catalysts of the type you are using, are extremely mortal....Even under the best
conditions. If you use enough, the Catalyst may often be used more than once. Heck, maybe even three times. Then, abruptly, perhaps mid-run, the
magic will abruptly stop working. Poisoned!
Gotta add a little fresh catalyst to finish up.
The nice thing about preparing Catalyst via Borohydride, is that there is no long induction period. It is ready to go in minutes.
[Edited on 27-6-2018 by zed]
[Edited on 27-6-2018 by zed]
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