Author Topic: For the vindication of Eleusis - Methylamine  (Read 28494 times)

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Chromic

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Thoughts
« Reply #20 on: April 13, 2004, 08:29:00 PM »
>the oxidation of formaldehyde to CO2 is avoided

From what I understand, that's not a problem. In fact, you WANT formaldehyde to be oxidized.

It's formaldehyde that's oxidized to form formic acid--that's rxn drives the reduction of the methyleneimine. That HCOOH is of course further oxidized (but ask yourself the question--what is reduced?) to water and carbon dioxide.

So if you answer that question, maybe it's that further oxidation of formic acid occurs because it's being used to reduce more methyleneimine.hcl. But that's just a guess. I don't know enough about the mechanism of this rxn -- except what's on

https://www.thevespiary.org/rhodium/Rhodium/chemistry/methylamine.html



Dimethylamine production is a problem and results from formaldehyde reacting with methylamine. (how would addition of alcohol supress that? other than to keep the temperature low, which is somethign that could be accomplished by slow heating anyways... my guess would be that perhaps removal of the formic acid helps drive the reduction of methyleneimine, a Le Chatlier principle thing but who knows... and but why not add methanol instead of ethanol? methyl formate would have a lower BP than ethyl formate)

Also, Organikum, are you sure what you got is pure methylamine hydrochloride? If so, I believe 10g of it will dissolve in less than 10ml of water. Check that to make sure it all goes into the water, if not, then you know you've got ammonium chloride as well. Eleusis made a mistake where he thought his yields were awesome when they were filled with mostly ammonium chloride

Abolt, make sure your methylamine hydrochloride was absolutely dry (not a sludge... it should be a rock hard CHUNK in your flask after distilling off the water) to make sure you really got all of the methylamine hydrochloride from the rxn via recrystallizing with methanol.

Organikum

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I know nothing about the rection mechanism and
« Reply #21 on: April 13, 2004, 10:28:00 PM »
I know nothing about the rection mechanism and I will stay away from making any guesses about it.
I found a patent.
I tried the procedure twice.
I posted the results.
The results were successfully reproduced by other bees.
(not only Bond_DoubleBond)

Regarding the solubility of ammoniumchloride in IPA I am very sure that the gained methylamine.HCl is quite pure. Had a look at the pic? Thats no ammoniumchloride for sure. As told I also did a chloroform and acetone wash.

I am sure we will find out what went wrong as Abolt tried it. If he likes to find it out of course.

Hey! It is even possible that adding NH4Cl to the reaction and do as always - without alcohol - will boost yields. But it wont reduce the reaction time and temperature as the addition of alcohol does very well.


ADDON: I believe the reaction mechanism as described on Rhodiums page is ONE POSSIBLE reaction mechanism, but by no way the ONLY POSSIBLE one - even not the most probable one I guess......


PS:

make sure your methylamine hydrochloride was absolutely dry (not a sludge... it should be a rock hard CHUNK in your flask after distilling off the water)


I never heard this before. Do you want to say "after distilling off the water and cooling down" ? Or do you actually say you can distill off the water UNTIL the MeAm.HCl is left as "rock-hard chunk"? Could you please clear this up for me?




abolt

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k.c.nicolaouoaouaoau was not a bullshitter.
« Reply #22 on: April 14, 2004, 09:58:00 AM »
Orgy

Did you add some NH4Cl, Abolt?

Yes, 25 grams. Otherwise, the amount and type of reactants were the same as mentioned in your write up.

Did you mix the alcohol and the acid before adding it to the hexamine and did you dissolve the hexamine in some water (partially at least)?

And did you give the hexamine some time to hydrolize before starting the reaction?


The Hexamine was crushed up and the liquid reactants were poured in straight on top.

The reaction was then heated and stirred on a water bath and was taken to reflux from room temperature over a period of 4 hours.

The reflux was then maintained for 75 minutes, before the formate portion was distilled.

The first fraction distilled at 67 Celcius.(???????)

Vacuum was then applied and the water portion removed.

BDB

Thanks for the tip. It appears that Terbium's reservations, about the temp that the reaction takes place, were correct.

It appears that the only real difference between SWIM's failure and the successes of others is the raising of the distillation temp of the H2O.

Chromic

Thanks, will do.


Bond_DoubleBond

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2 cents
« Reply #23 on: April 14, 2004, 11:13:00 AM »
abolt, swim doesn't think that you can derive any conclusions about your reaction when your distillation didn't produce either methyl or ethyl formate.

did you add hcl directly to the hexamine?  the following was taken from rhodium's site:

If the hydrochloric acid is added directly to the HMTA, a lot of it is lost, as ammonium chloride starts to separate almost immediately.

swim doesn't know what this means, but it could be a possible reason for your reacion failure.

when swim performed this reaction, he used a small excess of alcohol.  once the formate stopped distilling, swim turned up the temp and a small amount of ethanol was recovered (just under the amount one would expect based on the excess alcohol swim used).

this leads swim to believe that formate distillation is an accurate indicator of the reaction progress, and that if the temperature of the reaction mixture is controlled properly, the ceasing of distilling formate indicates the end of the reaction.

nearly exactly the amount of alcohol reacted that was expected, based on the amount recovered.  so, if exactly the amount of formate expected is produced, then the same yield could be expected of the meam.hcl.  theoretical yield from 100g hexamine is 139g meam.hcl.  org got 90% of that and that's with a chloroform wash that he suspects contained water, thus cutting into yield.  add that to normal product isolation losses, and it looks possible that this reaction produces near quantitative yields of meam with sub-atm distillation of the h2o.

just swims thoughts.

abolt

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************
« Reply #24 on: April 14, 2004, 11:26:00 AM »
abolt, swim doesn't think that you can derive any conclusions about your reaction when your distillation didn't produce either methyl or ethyl formate.

The B.P. of 67 Celcius is quite puzzling. Maybe a dodgy thermometer.

If the hydrochloric acid is added directly to the HMTA, a lot of it is lost, as ammonium chloride starts to separate almost immediately.

This is not the problem. AFAIK, Hexamine is a combination of Formaldehyde and Ammonium Chloride. The addition of HCl merely disassociates the two.

Personally, I think that the OH is not necessary.

Time and testing will tell.


Chromic

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more...
« Reply #25 on: April 14, 2004, 03:14:00 PM »
Yeah, I agree... what you've got really looks like MeAm. Ammonium chloride is barely soluble in even boiling IPA, so you'd have to have some pretty bad lab technique to end up with AmCl in your recrystallized MeAm...

The hard chunk that forms occurs once the water has been boiled off from the rxn only forms after it cools down (it's a bit of a slush while it's hot). If it's not a solid rock then you've left water in there and recrystallizations (either with IPA or MeOH) will give really low yields.

I'll have to try this sometime.

Rhodium

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French Methylamine Articles to Translate
« Reply #26 on: April 27, 2004, 08:16:00 PM »
Préparation de la monométhylamine
A. Brochet & R. Cambier

Bull. Soc. Chim. [3] 13, 533-537 (1895)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/menh2-hmta-1895.pdf)

The classic paper Brochet & Cambier paper Eleusis based his procedure on - they describe procedures using formalin and NH4Cl to produce methylamine, as well as HMTA and HCl, and mentions that methylal is evolved in the first procedure, as the commercial formalin contains methanol.
____ ___ __ _

Sur une nouvelle méthode de preparation de la méthylamine ainsi que sur la constitution de l'hexaméthylènetétramine
Trillat & Fayollat

Bull. Soc. Chim. [3] 11, 22-24 (1894)

(https://www.thevespiary.org/rhodium/Rhodium/pdf/menh2-hmta-1894.pdf)

This is an article Organikum will like - it is actually a preparation of methylamine involving the reduction of HMTA with Zn/HCl. They have gotten the structure of HMTA really wrong, but forgive them - they did this 108 years ago. They also describe the preparation of ethylamine by the Zn/HCl reductive amination of the acetaldehyde ammonia trimer*

* Also called Hexahydro-2,4,6-trimethyl-sym-triazine, and is commercially acailable. It can also be made by the addition of acetaldehyde dropwise to a 4x molar excess of concentrated aqueous ammonia, chilled in a freezing mixture [JOC 1973; 38; 3288]



biffman

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Temperature of boiling off
« Reply #27 on: April 28, 2004, 05:22:00 PM »
I was wondering about the final stage where you are evaporating the liguid to leave the methylamine.  Apparently it has been claimed that it can be done with or without vacuum. 
  As the liquid decreases and thus the concentration of methylamine increases in the solution during the final boiling off the temperature will increase I assume because of the increasing concentration of the MeamHCl.  I was wondering if this might be a point where dimethylamine might be produced since the temperature can go significantly above 100C.  Even with moderate vacuum. (Swim knows by experience).
  Swim was not willing to fire up the stronger pump just for this, so was wondering if anybody who has performed this monitored the temperature during the final evaporation of the liquid.

Organikum

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A quick question on the french articles: Can...
« Reply #28 on: April 28, 2004, 08:57:00 PM »
A quick question on the french articles:
Can somebody tell me if I am right when I assume that the french chemists in these times used CELSIUS as unit for temperature measurements? The article doesnt specify this further.

Thanks.
ORG


hypo

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yes
« Reply #29 on: April 28, 2004, 09:00:00 PM »
without looking at the articles in question: usually they do.
(fahrenheit = wacko german in the eye of frenchmen)


Sredni_Vashtar

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Units
« Reply #30 on: April 29, 2004, 12:33:00 AM »
Does anyone not use Celsius or Kelvin for scientific measurement nowadays?

Rhodium

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degrees
« Reply #31 on: April 29, 2004, 03:56:00 AM »
Yes, nowadays everybody uses °C or K, but those articles were written over a century ago.


abolt

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I was wondering if this might be a point where
« Reply #32 on: April 30, 2004, 07:52:00 AM »
I was wondering if this might be a point where dimethylamine might be produced since the temperature can go significantly above 100C. 

If the reaction has been held for a suitable time to allow for the formation of Methylamine, then slowly turn up the heat to distill the left over formate.

This leaves nothing but water and (hopefully) Methylamine ands maybe some residual Ammonium Chloride. You can now turn the heat up and safely distill the water at temperatures over 100.C.


biffman

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Good results
« Reply #33 on: May 02, 2004, 11:52:00 PM »
Thanks for all the info everyone. The method does work nicely and is definitely an improvement over swims previous method.  Quicker and less hassle.

Vaaguh

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temperature during distilling
« Reply #34 on: May 10, 2004, 03:43:00 PM »
Is it normal during the end of the distillation for the temperature of the boiling mixture itself to bee around 80-95 °C when there are still fractions comming over between 45 and 55 °C?

Or would this indicate that most of the ethanol has been distilled away?


Organikum

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This says your reaction is still running and...
« Reply #35 on: May 10, 2004, 05:08:00 PM »
This says your reaction is still running and ethylformate is still formed. Not sooo fast please. Anyways, 80°C to 95°C is still far away enough from the point of formation of dimethylamine (over 104°C as I remember) so this should be no problem at all.

Go a little slower perhaps - less heat - but actually I can see no problem at here. btw. at this temperature you havent even started to boil the water away - so this cannot be called "at the end of the distillation".

Yields ok?


Vaaguh

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slowed things down
« Reply #36 on: May 10, 2004, 06:06:00 PM »
The problem was that when the oil bath temperature was below 110 °C no distillate came over at all, which is probally caused by heat loss using a rather long vigreux column, so basically all the reaction mixture did was reflux the entire time with little distillate comming over while the temperature of the solution was starting to rise over 100 °C .

The column was switched for a simple still head and the oil bath temperature is lowered to 85 °C and the reaction temperature is now around 80 °C.

Distillate is comming over at 55 °C while the solution is not visually boiling.

Apparently Merck and Chemfinder both state that the bp of Methylamine HCl is 225-230 °C @ 15 mmHg, perhaps for purifcation purposes it is nice to vacuum distill the Methylamine HCl or will this bee an impossible task /unnecessary ?

Btw. Is it normal for the solution to turn a bit darker then being whiteish during the reaction ? All reagents used where labgrade except for the denatured 96% EtOH


Organikum

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Reflux was ok. Distillation needs no column,...
« Reply #37 on: May 10, 2004, 06:27:00 PM »
Reflux was ok. Distillation needs no column, what comes over now is the ethylformate, so everything is ok. Go on until no more formate comes over, then distill the water away. Temperature in the flask will rise over 100°C then - understood, but this doesnt matter as the reaction is over.

The residue in the flask was always very orange colored and the white crystals came after extraction/recrystallization from IPA as described.
Distilling methylamine.HCl is no good idea this stuff starts subliming at far lower temperatures. You will have no methylamine left when you reach 200°C+. Alcohol (IPA)extraction and recrystallization are the way to go.

Stop distilling the water away when the residue looks like a very wet mush or you will loose all methylamine. (sublimation, as told)
Dont worry about the color.


Bond_DoubleBond

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Hmmmmm...... Methylal........
« Reply #38 on: May 11, 2004, 02:37:00 AM »
I don't believe this works with methanol.  Judging by the temps that the distillates came over, very little methyl formate is formed (if at all), and a substantial amount of methylal is made.  _Lots_ of amcl was recovered.  No meam was isolated.

Temps were recorded at the top of a 200mm vigreux column and the distillate never came over at more than 1 drop / 4-5 seconds (i.e, heating was done slowly and carefully).  Nearly all distillate prior to methanol was collected in the 40-44c range.

I guess the meam never gets a chance at those low temps with the dimethoxymethane sucking up all the ch2o.

Save your methanol and hex.

madprosr

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benefits of stripping solvent with an aspirator
« Reply #39 on: May 11, 2004, 08:43:00 AM »
1) you and your lab don't smell like eleusis for the next week
2) your methylamine is not rearranged to dimethylamine
3) it's faster!