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Author: Subject: Decarboxylation of Glycine to Methylamine?!
Pumukli
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[*] posted on 28-3-2018 at 08:41


Seems to be a good idea.
Also, the note about not being pure product but a mixture of MeNH2 and others (I tend to think mostly ammonia).

In the benzene from benzoic acid (or what) thread they used fine metal mesh to improve heat conduction to avoid hotspots and achieve thorough even heating. Maybe it wouldn't hurt in this case either.
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[*] posted on 28-3-2018 at 16:06


I tried to determine the melting point and some of it decomposed like Ammonium Chloride, so like Pumukli mentioned, it is probably a mix of Methylamine and Ammonia.
Looks to me that too much heat and NaOH is too "aggressive" and converts a lot to Ammonium Chloride.
I would like to try the "sand method". What was your sand/glycine ratio?
Also I might go back to the "peppermint" idea. Maybe it´s more selective for Methylamine.
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[*] posted on 28-3-2018 at 16:13


Well, what reaction path is being followed in this sand-decarboxylation is difficult to project. Perhaps SiO2 somehow catalyses the reaction.

Sometime in the past, I read a paper wherein water separation was used, along with a ketone, to form the imine in bulk, followed by higher temperature decarboxylation of the imino-acid.

Had the paper somewhere. Darned if I can find it.

Copper Chromite might be a good catalyst. Seems to do the trick fer decarboxylaing nicotinic acid, to pyridine.

[Edited on 29-3-2018 by zed]
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[*] posted on 29-3-2018 at 01:56


Seems that we're all concluding that glycine decarboxylation with a strong base and elevated temperatures like carboxylic acid does it's impracticable with aminoacids, to produce even a modest yield of methylamine, like I said.

If this was a viable method, off course someone already had found some paper, research or recipe about that somewhere. But it's not the case until now.

Better follow the ketone-imine (schiff base) decarboxylation way, method that's well covered by many research studies and even here, at sciencemadness. See this thread:

http://www.sciencemadness.org/talk/viewthread.php?tid=74727&...



[Edited on 29-3-2018 by Chemi Pharma]
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[*] posted on 29-3-2018 at 14:13


Time will tell. It should be noted, that the method you are currently espousing, was not widely known a generation or so... ago.

The idea of producing easy tryptamine or phenethylamine, was quite alien.

Over the last 40 to 50 years, practical approaches to decarboxylation of aminoacids evolved.

At the moment, known pathways are limited. Surely there are more to be discovered.



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[*] posted on 30-3-2018 at 06:59


Quote: Originally posted by zed  

Copper Chromite might be a good catalyst. Seems to do the trick fer decarboxylaing nicotinic acid, to pyridine.
[Edited on 29-3-2018 by zed]


NileRed did once a video on decarboxylating nicotinic acid to pyridine with basic copper carbonate. I tried this too with Glycerine, but nothing happened. Maybe the temperature was too low or heating it in dry form (and badly mixed) was a problem.

I´ll try the peppermint method next week. I can´t see why this shouldn´t work.

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[*] posted on 31-3-2018 at 15:15


I've seen those videos. Copper Carbonate works poorly. Copper Chromite works very well. Seems to me Doug's Lab has a nice procedure.

I mentioned this because Nicotinic Acid, seems structurally quite similar to the imino-acids we are attempting to decarboxylate.

Copper Chromite accomplishes this decarboxylation, at right about 100 C.. A much lower temperature than that employed in most procedures.
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[*] posted on 17-4-2018 at 06:53


So, I have some updates and some things that I can´t figure out, so I hope you can help me.

A week ago I did the first decarboxylation:

I put 2g of glycine into 30mL of DMSO and 10 drops of the spearmint oil into a 100mL round bottom flask and connected it with a hose to a flask with diluted HCl solution. The glycine didn´t dissolve properly though.

When I started heating I noticed a little bubbling occurring at around 120 degree, which I thought was maybe the peppermint oil boiling, but then I saw, that it came from the undissolved glycine powder. Gas came over to the HCl solution. At the DMSO reflux temperature the bubbling got stronger and stayed constant. Since I didn´t used a reflux I stopped when the DMSO reached the hose. It was interesting to see, that the bubbling continued, even after I turn off the heat and it stopped, after all the undissolved glycine disappeared!

Then I boiled off the HCl solution, but in a moment, where I wasn´t watching, I burned it...

So I tried this again, but this time with less DSMO (20 mL) and 5g of glycine. Also I added a reflux condenser and switched to a phosphoric acid solution.
This time I noticed, that even without heating already a bit of gas came over! But it was a bit slower now, which I think was due to a lower DSMO amount. Then I realized that some crystals are forming in the condenser. I measured the temperature of the part of the condenser that wasn´t cooled and it was not the temperature at which glycine is boiling.
After some time the condenser was cloaked and a mini "explosion" occurred, where the rubber stopper jumped out of the flask. It was smelling like ammonia and reminded me of methylamine.

I stopped the reaction then and evaporated the H3PO4 solution and noticed, that it was reddish and stopped at about 5mL. Next I will see if cooling it will get me some crystals.

But I have the feeling, that there was some side reaction with the DSMO? I´ve read that it can methylate methylamine in acidic conditions, but might there be some reaction with the glycine? I mean the crystals in the condenser and the HCl and H3PO4 solution had a sulfuric and ammonia smell.
Should I use another solvent like turpentine?
But aside of that, it looks like the decarboxylation works really well!
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[*] posted on 17-4-2018 at 10:32


In Scr0t's pirrolidine synthesis there is a lot of turpentine, a small ammount of spearmint oil and no DMSO - although the reaction time is 20 hours at reflux temp. (around 160 C) and he had had solubility problems. He suggested using a small ammount of DMSO to help with the solubility though.

Link:
http://www.sciencemadness.org/talk/viewthread.php?tid=64791

So yes, turpentine may help.

On the other hand I can't really help with the side reaction, the reddish color of phosphoric acid soln. or the mini explosion. Btw. wasn't this later one caused by a simple mechanical blockade of the vapour path in the condenser? Was not this blockade caused by (methyl)ammonium-carbonate build-up?

Edit: added the link


[Edited on 17-4-2018 by Pumukli]
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[*] posted on 17-4-2018 at 13:50


Quote: Originally posted by Pumukli  
In Scr0t's pirrolidine synthesis there is a lot of turpentine, a small ammount of spearmint oil and no DMSO - although the reaction time is 20 hours at reflux temp. (around 160 C) and he had had solubility problems. He suggested using a small ammount of DMSO to help with the solubility though.

[Edited on 17-4-2018 by Pumukli]

I think I try to do it, like he did. Don´t think the DMSO will help with the solubility, since it dissolved gylcine really badly. But the reaction worked perfectly fine without it dissolving. Also I think that this reaction will proceed a lot faster.

Quote: Originally posted by Pumukli  

On the other hand I can't really help with the side reaction, the reddish color of phosphoric acid soln. or the mini explosion. Btw. wasn't this later one caused by a simple mechanical blockade of the vapour path in the condenser? Was not this blockade caused by (methyl)ammonium-carbonate build-up?

[Edited on 17-4-2018 by Pumukli]



The vapor which condensed, build up these crystals over time, so that they blocked the whole reflux condenser and the gas couldn´t escape anymore. Than the stopper flew out of the flask with a small bang. How do you assume, that it was (methyl)ammonium-carbonate?

I have put this reddish liquid in the freezer for one hour and it was syrupy. Normal water in this amount would´ve be frozen in 10 minutes.
I let it in the freezer now and then try to filter.

But has anyone an idea, if there was (or could be) a reaction between the DMSO and glycine? Didn´t had advanced synthesis chemistry in Uni...

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[*] posted on 17-4-2018 at 19:43


Quote: Originally posted by zed  
I've seen those videos. Copper Carbonate works poorly. Copper Chromite works very well. Seems to me Doug's Lab has a nice procedure.

I mentioned this because Nicotinic Acid, seems structurally quite similar to the imino-acids we are attempting to decarboxylate.

Copper Chromite accomplishes this decarboxylation, at right about 100 C.. A much lower temperature than that employed in most procedures.


Copper Chromite is specific for aromatic COOH groups in the presence of pyridine-like ligands. The traditional option is refluxing quinoline and copper powder. I don't believe it will work on glycine.

Doug's Lab procedure is mine from Prepub, tacked onto Magpie's pyridine thread, which is itself a modification of Ordenblitz's procedure.
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[*] posted on 18-4-2018 at 13:36


I'm suggesting that Copper Chromite might be effective for decarboxylating Amino-acid Imines.

[Edited on 18-4-2018 by zed]
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[*] posted on 19-4-2018 at 15:42


I mentioned using DMSO + spearmint as a catalyst once, but eventually realized that DMSO was an oxidizer under high-temperature conditions. Try using propylene glycol, if that's what you're trying to do. Maybe methylsulfonylmethane? Or even naphthalene? Or cetyl alcohol? The solvent barely seemed to matter if there was spearmint oil present.



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[*] posted on 19-4-2018 at 15:55


Napthalene might be a good idea.

In these days of difficult and expensive, solvent purchase, I can buy Napthalene for about 4$ per pint-pound.

Hadn't thought of it, and I like it.

Stinky though.

In the past, I have considered the use of Camphor.

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