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Wolfram
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Good way to Methylamine HCl?
Suppose I would like to make some mythylamine HCl. First I would put some hexamine in water add hcl reflux for six hours at 105 C on an oilbath. A mix
of methylamine and ammoniumchloride would form. If I would add a sultion of NaOH, freebase methylamine would be to expect, right?
Methylamine boils at 48 C so I could destilate over the methylamine and condens it down in hcl to gain methylamine HCl.
[Edited on 21-12-2003 by Wolfram]
[Edited on 21-12-2003 by Wolfram]
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fritz
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Are you shure you will have a mixture of ammonium- AND methylamine-HCl??
I would expect that you have only NH4Cl because in acid solution urotropine will split in ammonia(=ammonium-salt) and formaldehyde.
If your method really works try some other separating method (extracting the methylamine-HCl with absolute EtOH) destillating the mixture with NaOH
would also release ammonia. So in the end you´ll be were you started!
If your method fails you may perhaps try this:
In a 500ml flask add 80g (26ml) bromine to 30g acetamide with good cooling add a solution of 50g KOH in 350ml water until the red colour of the
bromine deceased and the solution is yellow. This solution you add to a warm (70-75°C) solution of 80g KOH in 150ml water. you maintain warming
(ca.15-30min) until the solution is colourless then you distill the methylamine until the condensing liqiud reacts no more alkaline. (collecting the
destillate in 100ml 5n HCl) The solution of ammonium- and methylamine-HCl is evaporated to dryness and dried overnight in a vacuum desiccator. It is
extracted by boiling with abs. EtOH. The filtrate (solution of methylamine-HCl ) is boiled to a small volume and after cooling the methylamine-HCl
precipiates. It is washed with EtOH and dried in a desiccator.
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Organikum
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methylamine boils at - 6°C, but it will not distill over from an aqueous solution same as ammonia wont do.
https://www.rhodium.ws/chemistry
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unionised
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Interesting logical / grammatical point. Technically it is true to say that methylamine won't distill from water in the same way that ammonia
won't. It's just that it's a bit misleading. Both will. You can distill both bases to recover them from water.
If you have a saturated solution of methylamine at 12.5 C (where 1154 vols of the gas are soluble) and heat it to 25 C where only 959 vols are
soluble, the difference will come out of solution. Those 2 points are the only data I have on the solubillity. I would presume that further heating
will drive more of the amine from solution.
I have a vague memory that the standard lab prep of methylamine is the reaction of ammonia and formaldehyde in acid conditions, but I'm not sure.
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Organikum
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why not....
To 1mol hexamine (about 140gram) dissolved in 3 liters dH2O is added over 4 hours 2mol Zn (about 125gram in theory, use at least 150gram) in SMALL
portions with strong stirring and so much muriatic acid that the reaction stays slightly acidic all time. Temperature is roomtemperature or below and
should STAY so. Cool it so necessary - more water doesnt hurt so icecubes are fine....
Stirr on for at 6 to 12 hours.
Basify with NaOH.
Smell what you wanted to smell poor boy.
Steamdistill directly into some 15% HCl.
Methylamine.HCl - bingo.
Go to Rhodiums page for description of further workup, chloroform is NOT needed if done the described way - the IPA extractions are all whats
necessary to get rid of ammoniumchloride. No dimethylamine is formed.
enjoy.
yields: from 85% up to theory
[Edited on 21-12-2003 by Organikum]
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fritz
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I´m sorry but I insist in my explanations!
Why should ammonia/methylamine not boil from water?
You will have a equilibrium: on the one side water and Ammonia/methylamine on the other side hydroxide protonated ammonia/methylamine:
NH3 +H2O <> HN4+ + OH-
MeNH2 + H2O <> MeNH3 + OH-
so if you boil such a mixture ammonia will evaporate and the first equilibrium will be shifted to the left side. (never boiled ammonia-solution??!?)
Why should the same not happen to methylamine? O.k. the base strength of methyl amine is higher than that of ammonia but at room temperature it´s
also gaseous so it would evaporate which will led the secon equilibrium also to be shifted to the left side!
The evaporation will also take place in alkaline solution so the OH- ions will shift both equilibria to shift to the left side because OH- is the
strongest base in water and so it will deprotonate every base in water. I found this method in a book about organic chemistry ... the only thing I
really trust are books. so where would it lead if we can´t trust our tresuries of chemistry knowledge anymore??!!?????
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Organikum
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of course it boils.
of course you will be able to boil some ammonia or methylamine out of an solution of sufficient strength.
Of course there will water come over with the ammonia and methylamine.
Lots of water.
Wolframs method works.
Yours also - except the drying part.
Mine works best.
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Wolfram
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Thank you very much
Thank you very much for your answers. Now where is it written that methylamine boils at -6 C? In Aldrich its written +48C. Ammonia boils at -50 or
something like this so I will NOT get a mixture of ammonia and methylamine since ammonia will not condens, but will leave to the air.
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unionised
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The vapour pressure of water at 25 C is about 20 or 30mm Hg. That's about a 30th of an atmosphere. The methylamine will be accompanied by water
but about 29/30 of it will be the product you want.
OK, in reality the figures will not be quite that simple due to association. I still think it's about the right order of magnitude. The bulk of
the stuff that distills will be the more volatile material.
EDIT
Just seen Wolfram's post.
It is so written in Merck and in Sax's dangerous properties of hazardous materials. OTOH Aldrich gives the Bpt of the solution they sell as 48C
[Edited on 21-12-2003 by unionised]
[Edited on 21-12-2003 by unionised]
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Mumbles
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Perhaps give this a try? http://www.orgsyn.org/orgsyn/default.asp?formgroup=base_form...
I can just get those chemicals much easier than Hexamine.
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vulture
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Don't forget that methylamine might just form an azeotrope with ammonia. Compounds with similar behaviour in water solution often do that.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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unionised
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In theory you can separate them on the grounds of the difference in bas strength, but I wouldn't like to have to.
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Organikum
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Wolfram
methylamine is a gas at roomtemperature.
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KABOOOM(pyrojustforfun)
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Adiabatic: that's the exact reason they didn't mention it! unless they had an otc source for their NM otherwise it's kind of ***** to
make NM and convert it to MA
we should seriously take glycine into account.........
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Wolfram
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What is the reference that methylamine boils at 6 C?
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Organikum
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the lazy way
- Dissolve some hexamine in water in a plasticbottle (PET is fine).
- Add double the amount of water needed for dissolving.
- Add quite a lot of Al (foil) or zincfilings or ironfilings or alltogether.
- Add some HCl.
- See the bubbling start.
- Add more HCl from time to time until you smell a salmiac stench.
- Shake.
- Place on heating - 50C is ok
- Shake.
- this is continued over several days until no more salmiac stench is present, if necessary add more metal or HCl.
- Basify.
- Steamdistill.
- Methylamine in good yields.
Using a strong stirrer and Al/Zn/Fe powder speeds up the reaction to about 24 hours to completeness. Plain Al-foil and shaking from time to time may
take 2 weeks.
Dont overacidify!
Keep the broth slightly acidic so the metal reacts - not more.
Time
is
the
key
Hey! Thats the hit! Isnt it? No dimethylamine btw. And keep the bottle mostly closed - it can take the pressure, vent it once a day and nosecheck the
ammoniumchloride (salmiac) content, then squeeze it and close it again.
shake it baby, shake it.......
 
EDIT:
Repeated tries and a check of theory showed up that no DI-methylamine but TRI-methylamine is a byproduct of this synthesis.
About 1 mol TRI-methylamine to 3 mole MONO-methylamine.
Sorry my bad.
for a conveniant synthesis of methylamine without the need of zinc or other metals look for a followup post of mine in this thread - after the picture
- soon to come to the theatre in your town also....
To honour Polverone: this is a modified procedure after a german patent from 1898.
19th century rulez!
[Edited on 24-2-2004 by Organikum]
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guaguanco
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| Quote: | Originally posted by Wolfram
What is the reference that methylamine boils at 6 C? |
The CRC lists the BP as about -6 C
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unionised
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's funny, I thought I mentioned a couple of refs to the bpt on 21/12/03.
Anyway, don't forget while playing with mixtures of HCl and HCHO that you can generate
bis(chloromethyl)ether which is really quite bad for you.
[Edited on 11-1-2004 by unionised]
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Organikum
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But how does it look like ?
Thats how it looks like !
Still a little IPA-wet, the crystals get glassclear after this evaporated.
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Organikum
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Better method...
The ratios used:
100g hexamine
100g water
310g HCl 30%
100g ethylalcohol denat.
20g ammoniumchloride
145g Methylamine.HCl in theory
The hexamine from fuel tablets (which are 100% pure here where I live) was dissolved in 100ml water - not all hexamine went into solution. The HCl and
the alcohol where mixed and chilled and then slowly added to the hexamine, at start some fumes evolved. This mixture was put in a 2l flask which was
equipped with a vigreux column (40cm) and a downright condensor, a thermometer into the flask and a thermometer at top of the column. The column was
cooled by a fan (12V/8cm computerpart). Boilingstones (broken flowerpot) were added and heat applied by means of a waterbath.
At 75°C boiling started. The reaction was held at a steady reflux for about 2 hours then some liquid started coming over at 50°C to 60°C (measured
on top of the column). Probably the ethylformate - what else. This ceased after about one hour and for the good of it the reaction was refluxed for
one more hour. Then the column was removed and the water distilled away under aspirator vacuum. The temperatur in the flask never got higher than
90°C. As the water was mostly removed and a yellow slush remained in the flask, IPA was added and the slush extracted. Three portions of IPA -
200ml/100ml/100ml - brought to a boil and decanted. A snowwhite remainder stayed in the flask - ammoniumchloride.
The extracts which of course contained some ammoniumchloride were joined and set up for distillation. About one third of the liquid was boiled away
(azeotropic removal of remaining water) - some heavy bumping appeared at the beginning also fresh boiling stones had been added. This was done to
remove remaining water by the azeotrope. The remainder was filtered hot through a flutet filter for to remove the last ammoniumchloride.
The IPA was put on my balcony (a usual freezer might be substituted here) and forgotten. After about 12 hours the jug was full of beautiful crystals,
the remaining IPA was poured out and - concentrated again and treated like before.
The crystal were spread out and dried on a hot waterbath - careful - methylamine is VERY hygroscopic!
A chloroform wash produced almost no dimethylamine - I actually guess there was no dimethylamine at and the three grams produced by the chloroform
wash were by traces of water present in the chloro.
Yield: 125g, 145g would be theory so thats ok for me.
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Mendeleev
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Why does everyone seem to prefer methods using hexamine? I personally think the hexamine route is a poor idea because it wastes precious hexamine
which would be better put to use making RDX, and requires steam ditillation. I personally prefer the ammonium chloride and formaldehyde method I
discovered on rhodium. It requires about 2 L of formaldehyde and 1 kilogram of ammonium chloride, both of which are dirt cheap, probably costing
around $15 for both. Simply mix, heat until the ammonium chloride is fully dissolved, leave at around 104-106 degrees Celcius for about 3 hours, then
increase the heat to evaporate the water, until you see ammonium chloride precipitating. At this point turn the heat off and begin cooling the
reaction vessel and its contents to a little under 20 degrees Celsius, and filter the solution (vacuum helps). The filtrate is then transfered to a
different vessel and heated to drive off water until temperature reaches 160 degrees Celsius, at which point a vacuum is applied. The vacuum should
cause the temperature to drop several degrees, but when it reaches 160 again you are done. Once the methylamine is cooled down all that remains is to
wash it with chloroform. I think there are similar methods discussed on other websites. Aside from hexamine and this methods there are also
nitromethane, acetamide, Hoffman rearangement, ammonolysis and direct reaction of ammonia and methanol in the presence of a catalyst methods, but all
seem much more difficult.
[Edited on 26-2-2004 by Mendeleev]
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guaguanco
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Well, hexamine isn't particularly expensive or hard to get, so it doesn't really matter if you sacrifice some along the way. I suppose it
all depends on what starting materials one has access to.
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Marvin
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Since the usual route to hexamine is to mix solutions of ammonia and formaldehyde I really dont see why making it from formaldehyde and an ammonium
salt is such a big improvement. Regardless of if you buy your hexamine or have to make it the advantage just seems to be semantic.
[Edited on 26-2-2004 by Marvin]
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Organikum
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The procedure as described can be done with ammoniumchloride and formaldehyde also - no problem. The HCl hydrolizes the hexamine to these two
compounds. The the question what to use is academic and depends solely on the availability of the starting material.
So I can buy hexamine OTC and cheap around the corner in form of fuel tablets named "HEXA" (hehe...) , but as I cannot buy formaldehyde OTC
I use hexamine. It has also the advantage in my eyes that it is a nice compressed form of formaldehyde and ammonium, not smelling and to store without
problems.
If somebody is not able to adjust the ratios used to NH4Cl and formaldehyde 40% aqueoous solution - not my problem.
Goodbye.
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acx01b
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well
the man says why not use directly Formaldehyde and NH4Cl:
because you will get 1st Hexamine!
so i ask to you: why not directly use Hexamine ?
then:
does anyone know how to obtain non hydrated ammonia or methylamine from aqueous ammonia or aqueous methylamine freebase ?
I'd expect that CaCl2 would work ?
but maybe im wrong.
Anway, do you know an other way than drying agents ?
[Edited on 6-5-2004 by acx01b]
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