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DIBALL
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Decarboxylation of Glycine to Methylamine?!
Well in theory it should be possible, or not?
I tried it with 1g of Glycine in Propylenglycol (not really soluble when cold) and 1g of Cyclohexanone and refluxed it for an hour. In my theory it
should be released as a freebase gas, but nothing happened. The solution turned orange (probably due to the high temperature) and not more.
I know that alcohols dissolve Methylamine pretty well (30% by weight in Ethanol), but I couldn´t smell any of this stuff anyway.
Just for fun I tried heating the Glycine with basic copper carbonate (like in the Niacin to Pyridine synthesis), but as I expected nothing happened.
Was the temperature too low (in the first experiment) or anything else wrong? Could this even work? I mean decarboxylations of Pyridine and Tryptophan
for example have quite big molecules and Glycine is small...
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Chemi Pharma
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@Diball, aminoacids are generaly decarboxylated in presence of ketones at reflux, withouth propylenglycol as a solvent, as far I know. May be that's
the problem.
Try to mix glycine with acetophenone, knowed as a ketone that's will give you better yields and DMSO as a solvent if you really think that you need a
solvent to mix them, refluxing at 150ºC.
read this thread about the decarboxylation of aminoacids. May be it enlighten your ideas:
http://www.sciencemadness.org/talk/viewthread.php?tid=74727&...
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DIBALL
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As far as I know, the solvent is there to archive high temperatures and Propylenglycol has a BP of 188°C, also I added Cyclohexanone, which should be
the catalyst. Acetone should work as well. I used this as inspiration: https://erowid.org/archive/rhodium/chemistry/tryptophan.html
Don´t think the solvent is the problem, though it is not optimal.
[Edited on 15-3-2018 by DIBALL]
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Chemi Pharma
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But I think you're with a solvent matter. Propylenglycol don't dissolves well glycine and I think it's interfering with the ketone catalisys of
glycine decarboxilation. Also, propylenglycol can absorbe all methylamine and carbon dioxide the reaction produces and may be it's the cause you're
sniffing nothing smelling from the reaction vessel.
How much propylenglycol are you using in therms of mol equivalent?
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DIBALL
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I used way to much of PG. If think it was around 20-30mL. But since it has such a characteristic smell and the temperatures were really high, I
thought maybe a bit would escape. Maybe I should try with a different solvent. Do you know the exact process of this decarboxylation? I honestly
don´t get it, what difference a ketone makes in this reaction, only that it might produce an intermediate with the amine.
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LearnedAmateur
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What was your exact procedure, starting from glycine? There may be clues in what steps you took. I’ve never tried a decarboxylation myself but I and
others may be able to offer some insight into what went wrong..
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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Chemi Pharma
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I could answer your question here in this space. But it would be a tiring answer.
Again I tightly recommend you to use DMSO instead propylenglycol.
You'd better read the thread I suggest you to read before:
http://www.sciencemadness.org/talk/viewthread.php?tid=74727&...
If you are just interested on the mechanism of aminoacids decarboxilation mediated by ketones I'm attaching the paper I attached there again to you.
Read it:
Attachment: Decarboxylation by heat of a-Amino-acids in the Presence of Ketones.PDF (642kB)
This file has been downloaded 688 times
[Edited on 15-3-2018 by Chemi Pharma]
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Shiva_Inorganic
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I had tried this before. It decomposes into Methylamine and Carbon dioxide when heated with Soda lime.
H2NCH2COOH ----> CH3NH2 + CO2
But not sure how to separate Methylamine from carbon dioxide. Still thinking of it.
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DIBALL
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1g of Glycine was dissolved in 10mL of PG. Since it didn´t dissolve properly, 20mL of PG were added and around half of it went into solution. 1mL of
Cyclohexanone was added and refluxed for 1h.
@Chemi Pharma
That paper looks great! Thanks for that!
So its a Schiffs base which is formed... that should mean, that the reaction is water sensitive? Didn´t dry any of the reagents or solvents...
Well I will try it again with DMSO or acetophenone
Quote: Originally posted by Shiva_Inorganic  | I had tried this before. It decomposes into Methylamine and Carbon dioxide when heated with Soda lime.
H2NCH2COOH ----> CH3NH2 + CO2
But not sure how to separate Methylamine from carbon dioxide. Still thinking of it.
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What did you exactly do? Methylamine could be bubbled in a HCl solution. Sounds interesting
[Edited on 15-3-2018 by DIBALL]
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DraconicAcid
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| Quote: Originally posted by Shiva_Inorganic | I had tried this before. It decomposes into Methylamine and Carbon dioxide when heated with Soda lime.
H2NCH2COOH ----> CH3NH2 + CO2
But not sure how to separate Methylamine from carbon dioxide. Still thinking of it.
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Seriously? Carbon dioxide can be easily absorbed by solid NaOH. Or the methylamine can be absorbed by strong acid, then released by addition of
strong base.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Shiva_Inorganic
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I did not bubble it through HCl as I wanted it as a free base. But, I bubbled it through water and the liberating gas turns wet red litmus blue. It
has a disagreeable odour. I tried to ignite it but it did not burn probably due to the presence of CO2.
[Edited on 15-3-2018 by Shiva_Inorganic]
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Chemi Pharma
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| Quote: Originally posted by DIBALL | @Chemi Pharma
That paper looks great! Thanks for that!
So its a Schiffs base which is formed... that should mean, that the reaction is water sensitive? Didn´t dry any of the reagents or solvents...
Well I will try it again with DMSO or acetophenone |
No absolutely water sensitive, cause the subsequent hydrolisys of the Schiffs base requires an acidic or basic medium. I think the reagents don't need
to be absolutely dry. The paper didn't say that. However it's what I think, I don't have any study to base this.
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Shiva_Inorganic
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Yeah good idea. Methylamine can be used as a scrubber to absorb various acidic gases. As you rightly pointed out, CO2 can be removed by passing it
over solid NaOH. I need to find a proper apparatus to try it though.
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Shiva_Inorganic
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Unlike other chemistry youtube channels, I do not have many apparatus. But, I have a fair number of chemicals though. Using them, I have been posting
videos about some rare chemicals like Sodium phosphide, Nitrosyl chloride, Nitrosyl bromide etc..
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LearnedAmateur
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| Quote: Originally posted by DIBALL |
1g of Glycine was dissolved in 10mL of PG. Since it didn´t dissolve properly, 20mL of PG were added and around half of it went into solution. 1mL of
Cyclohexanone was added and refluxed for 1h.
[Edited on 15-3-2018 by DIBALL] |
Oh right, I would’ve thought that sodium hydroxide would’ve been involved somewhere along the line. When I think decarboxylation, I imagine that
CO2 is removed as a carbonate like Shiva mentioned during a dry distillation. R-COONa + NaOH + heat -> Na2CO3 + 2 R-H. Maybe try this method out?
If you don’t have access to NaOH then it can be produced from the carbonate by heating. Acidifying the methylamine after distillation will help with
workup because it can be re/crystallised, the CO2 and subsequent carbonic acid becomes a non-issue as it is displaced by e.g. HCl, and the salt is a
convenient form to store. Maybe I will give this sort of thing a go, I believe I have some lysine lying around somewhere so I can make
1,5-pentanediamine.
[Edited on 15-3-2018 by LearnedAmateur]
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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DIBALL
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| Quote: Originally posted by Chemi Pharma | [
No absolutely water sensitive, cause the subsequent hydrolisys of the Schiffs base requires an acidic or basic medium. I think the reagents don't need
to be absolutely dry. The paper didn't say that. However it's what I think, I don't have any study to base this. |
Okay, I was already wondering, why no synthesis on erowid mentions a dry solvent. Dry solvent it is then!
@Shiva_Inorganic
Can you explain how you did your reaction and to what temperature you heated it? You could bubble the freebase into ethanol or something else which
dissolves it quite well.
@LearnedAmateur
NaOH is available. But it sounds almost to easy. Do you have a reference?
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LearnedAmateur
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Of course, and it is so easy that’s why I thought it was the route you were trying to accomplish!
https://www.chemguide.co.uk/organicprops/acids/decarbox.html
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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Chemi Pharma
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| Quote: Originally posted by LearnedAmateur | | Oh right, I would’ve thought that sodium hydroxide would’ve been involved somewhere along the line. When I think decarboxylation, I imagine that
CO2 is removed as a carbonate like Shiva mentioned during a dry distillation. R-COONa + NaOH + heat -> Na2CO3 + 2 R-H. Maybe try this method out?
If you don’t have access to NaOH then it can be produced from the carbonate by heating. Acidifying the methylamine after distillation will help with
workup because it can be re/crystallised, the CO2 and subsequent carbonic acid becomes a non-issue as it is displaced by e.g. HCl, and the salt is a
convenient form to store. Maybe I will give this sort of thing a go, I believe I have some lysine lying around somewhere so I can make
1,5-diaminopentanoic acid. |
I think a misunderstood are happening here. The goal is to decarboxylate an alfa aminoacid to an amine with a less carbon and not decarboxylate a
carboxylic acid or it's salt to an alkane with a less carbon. Isn't it?
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LearnedAmateur
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Decarboxylation removes one carbon atom as, effectively, CO2 which is taken up by the hydroxide to form the carbonate. If you had a standard
carboxylic acid like acetic acid, methane would be produced - what is happening with glycine is analogous, just replace a H on the adjacent carbon
with NH2, hence you get methylamine. Also I made a mistake in the last part which has been corrected.
[Edited on 15-3-2018 by LearnedAmateur]
In chemistry, sometimes the solution is the problem.
It’s been a while, but I’m not dead! Updated 7/1/2020. Shout out to Aga, we got along well.
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Shiva_Inorganic
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Nope Chemi. Decarboxylation of amino acid is one of the methods to prepare primary amines. You can even use Barium hydroxide (anhydrous) to prepare
Methylamine. Glycine (aminoacetic acid) decomposes in the similar way when you heated with a strong base.
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Shiva_Inorganic
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DIBALL, not sure about the temperature. If you have the burner, heat it for 2-3 mins. I heated the mixture until it turns black for Methane
preparation and it worked wonderfully well.
https://www.youtube.com/watch?v=tdFLvCTBJ0o
[Edited on 15-3-2018 by Shiva_Inorganic]
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Chemi Pharma
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| Quote: Originally posted by LearnedAmateur | | Decarboxylation removes one carbon atom as, effectively, CO2 which is taken up by the hydroxide to form the carbonate. If you had a standard
carboxylic acid like acetic acid, methane would be produced - what is happening with glycine is analogous, just replace a H on the adjacent carbon
with NH2, hence you get methylamine. Also I made a mistake in the last part which has been corrected. |
Do you have I paper or a study to base this? I never heard about decarboxylating amino acids to amines with one less carbon with alkaline base before.
If so could you post it here? I will enjoy to read about it.
[Edited on 15-3-2018 by Chemi Pharma]
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Chemi Pharma
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| Quote: Originally posted by Shiva_Inorganic | | Nope Chemi. Decarboxylation of amino acid is one of the methods to prepare primary amines. You can even use Barium hydroxide (anhydrous) to prepare
Methylamine. Glycine (aminoacetic acid) decomposes in the similar way when you heated with a strong base. |
Do you have some paper or study to base this? Is the same question I made to @LearnedAmateur. If so I will enjoy to see that and read about this
strange theory behind this kind of reaction. Post it here please.
[Edited on 15-3-2018 by Chemi Pharma]
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DIBALL
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Just mixed NaOH and Glycine in a test tube and after heating there was a reaction that released some gas, but the products looked like water and some
solid. More heating released ammonia gas...
@Shiva_Inorganic
Nice Youtube channel!
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Boffis
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@ Diball; when you heat glycine with glycols you get cyclitisation to to piperazine-2,5-dione. Alanine yields the 3,6-dimethyl analog. Once formed
these compounds cannot form a Schiff base type condnsation product so I suspect that once formed these compompounds resist the effects of a ketone.
The formation of these piperazines should occur with any alpha amino acid but in practice only the simplest of the amino acid undergo this type of
reaction as far as I am aware.
I think that shive_inorganic is onto something with his sodalime degradation. Has anyone tried heating calcium glycinate and calcium oxide to
decomposition? The idea of the extra calcium oxide is to remove an extra CO2 and reduce the formation of C3 compounds (as in the case of acetone from
calcium acetate).
Diball, in your last post how did you determine that the gas released was ammonia? Methylamine smells much like ammonia.
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