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chemrox
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original post?
Is there an original post on this so those of us new here can catch up? If not could you (magpie) make one we can all follow?
Looks like a simple method and preferable to hexamine in may respects. Also provides a method for obtaining Br2 which is easy enough to buy .. but
the shipping costs !!!
Thanks
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Magpie
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@chemrox: I'm not sure what you mean by "original post." Please explain.
The single most important condition for a successful synthesis is good mixing - Nicodem
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bio2
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Magpie, How did you make the flask support for the triple
neck I see on the hotplate?
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Magpie
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bio2 this is just an iron ring like you would normally use to support a wire gauze and flask.
It probably wasn't needed in this application as the hotplate itself would provide support. But the ring does distribute the weight better. The
reason I had the ring there is so that I could place a gauze on it and heat with a bunsen burner when all the N-bromoacetamide had been added. I was
mostly using the stirrer-hotplate as just a stirrer as the reaction is exothermic.
The single most important condition for a successful synthesis is good mixing - Nicodem
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bio2
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I see. Try a stainless steel large strainer turn it upside
down and a round bottom flask can be used to imprint
a depression. It will support the flask
directly on the ceramic top or in an oil bath.
[Edited on 19-1-2007 by bio2]
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xwinorb
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Magpie :
To test your supposed methylamine ( not a very scientific test, but fast and easy ) :
Mix a small portion of your final product with a similar portion of NaOH, both dry, powder, over a small dish. Now drip in a drop of water. It should
fizz and make bubbles, the smell of methylamine should be very evident.
One word of caution, I think methylamine with a high content of ammonium chloride will smell like methylamine. The smell of methylamine seems to mask
the smell of ammonia.
I have used this method to test the first crops of ammonium chloride ( when making methylamine via hexamine ) and they smell mostly like methylamine,
despite being mostly ammonium chloride.
Pure ammonium chloride smell different though, exactly like ammonia.
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Furch
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It's not a very scientific way to determine the purity or the presence of one or the other... But in my experience the two taste quite different. We
all know the taste of ammonium chloride, and should quite readily be able to distinguish it from that of methylamine... I believe taste is less
deceiving than smell in this case.
Note though, that methylamine is poisonous, so only taste very little (less than a milligram), then spit it out immediately.
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garage chemist
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I did a quick experiment with some pure methylamine HCl (made by neutralizing commercial 40% CH3NH2 with HCl and evaporating in a warm place):
I added some 99,5% Isopropanol and boiled for a few minutes, then decanted and let cool. Crystals soon appeared.
However, their amount was not very large. In order to recrystallize MeAm-HCl this way a lot of isopropanol has to be used.
A smart alternative would be to use a soxhlet extractor!
I repeated the experiment with some ammonium chloride instead.
After boiling, decanting and cooling, absolutely no crystals appeared.
So extraction of the crude (dry!) salt with hot isopropanol, preferably in a soxhlet to reduce isopropanol consumption, seems like a good way to
purify the methylamine-HCl.
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Furch
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A very good initiative, Garage chemist.
Regardless of your experiment, I agree that IPA is the solvent to use for purifying ammonium chloride contaminated methylamine hydrochloride.
- Furch
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pantone159
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Has anybody tried using n-butanol for the separation? The OrgSyn synthesis mentions this as good, since NH4Cl dissolves in it hardly at all.
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Furch
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Pantone, in accordance with Garage Chemist's experiment mentioned above, the methylamine acquired from recrystallization from IPA is good enough for
any amateur chemist's purposes.
0.6 g ammonium chloride dissolves in 100 ml absolute ethanol, and even less in IPA.
- Furch
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Klute
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Klute's got some acetamide on hand, and wanted to try the hofmann rearrangement to methylamine... Unfortuanly, where he lives, Calcium Hypochlorite
isn't available anywhere anymore... Only hypochorite sources are either 10% max sodium hypochlorite solution, or solid sodium dichloroisocyanurate,
which gives hypochlorite and cyanuric acid in water... He wanted to try a reaction with 40gr acetamide, with the sodium hypochlorite solution...
After some calculation, he realized he need 640ml of that solution for 40gr acetamide, with excess to compensate the solution not being as strong as
indicated...
Wouldn't that be too diluted for that reaction? This could mean smaller yields, but at the same time, the exothermic reaction will be much
smoother, and letting the bleach react with the acetamide for say 4hours before adding the NaOH could compensate... But damn, distilling with a 1 L
flask for 25gr MeNH2... In any case, this really isn't scalable....
So the other possibilty is the dichloroisocyanurate... would cyanuric acid interfer with the reaction? I'm scared so...
Has anyone got experience with using sodium hypochlorite solutions with this recation? Or even dichloroisocyanurate? Could cyanuric acid interfer?
Klute guess nitromethane reduction would be more practicale... Could 10% MeNO2/MeOH azeotrope be used as is in either Sn or Fe acid reductions? In
Klute's experience, using 10% azeo kills a Al/Hg reaction... too diluted...
Any advice appreciated
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Furch
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A couple of years ago I reduced nitromethane by Fe/HCl and reflux overnight... The yield was a little more than 50%, but IIRC my workup wasn't as
thorough as it would've been today, so you can probably get a better yield out of that particular reduction.
IIRC I used the molar ratios from Vogel's or March's straight off, with a slight excess of everything. Don't remember the concentration of the HCl
though... Probably around 10-15% or so.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Sauron
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The Org.Syn. procedure has the virtue of cheap feedstocks. Hard to get much cheaper than formalin and ammonium chloride.
Switching to nitromethane reduction and you are consuming chloroacetic acid and sodium nitrite instead.
You could also reduce formaldoxime (from formalin or paraformaldehyde and hydroxylamine hydrochloride.)
Or generate methyl chloride from methanol and TCT and ract it with ammonia.
There are routes starting with iodomethane but that is costlier and naking it from methanol and I2 means using a valuable scarce reagent (iodine.)
So take your pick.
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Furch
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The nitromethane route is superior to both formalin/NH4Cl and methyl chloride on ammonia in that reduction of nitromethane gives mono-methylamine
period, no di- or tri-variations, which without a doubt methyl chloride on ammonia would, and also formalin/NH4Cl.
The same polyalkylation problem would arise from using any methyl halide on ammonia, including methyl iodide.
IMHO, a rule of thumb is that alkylation of amines by alkyl chlorides is almost always the last and desperate way out of a synthetical dilemma.
If it's purity you want, then I recommend you go for the nitromethane or acetamide route. If it's quantity you want, go for formalin/NH4Cl, then
recrystallize from IPA.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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nightflight
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What about the Hexamethylentetramine with HCL synth? -Are there any write-ups?
The Hex is OTC and readily available, a little more expensice than NHCl4, though, but it compensates, if your supplier is on the expensive site, for
Formaldehyd.
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Sauron
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Actually I have more use for dimethylamine and methylamine.
Here dimethylamine is controlled while methylamine is not.
Rather silly reallt.
You are correct about MeNO2 giving only the monomethylamine but I would not be very happy with a 50% yld. in reduction step.
And in the nitromethane thread so many are griping about having trouble getting sodium nitrite. At least I don't have that hassle, and I have
chloroacetic acid on hand as well. Though next time I think I'll buy a few kg of the sodium salt.
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Furch
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Of course, I used formalin/NH4Cl as a joint name for all the formalin/ammonium/hexamine variations... After all, they are principally the same
(hexamine is hydrolyzed to formalin and ammonium chloride in an acidic environment).
You should be able to find the hexamine route easily in Rhodiums archives.
Sauron, that is indeed very weird! Here nitromethane is OTC, and quite cheap too... In contrast to chloroacetic acid and sodium nitrite. I'll probably
research the Fe/HCl reduction futher sometime, as I'm quite convinced the yield could be significantly increased if more effort is put into it. I'm a
bit puzzled that nobody has done a serious write-up on that particular topic... After all, all the chemicals are dirt cheap (except maybe MeNO2 in
some cases).
The difference in legislation of precursors when looking at several countries never ceases to amaze me!
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Rosco Bodine
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You should get way more than a 50% yield from nitromethane via reduction using aluminum isopropoxide or perhaps aluminum amalgam directly , or with
some other alcohol perhaps methanol or ethanol ....or perhaps using toluene or xylene for a solvent to moderate the reaction . I know aluminum
amalgam does the trick , but I don't remember the exact conditions .
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Klute
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In my country, formalin is hard to get in decent quantity.. Pharmacies will give you 25-50ml maximum... Also, no hexamine tablets have been found yet,
people in specialized camping shops don't even know what they are... From what I heard the workup is quite a hassle... (takes time)
As Klute hasn't got much time, he will not try the sodium hypochlorite hofmann rearrangement right away, but go on the MeNO2 reduction... Max
concentration of the nitro is 15%, so when distilling about 500ml of racing fuel, he gets roughly 350ml 10% MeNO2/MeOH azoetrope, 35ml nitromethane,
and 45gr oil as residu...
He is planning on doing an Al/Hg with 35ml pur nitro and perhaps 100ml of the azeotrope which would give a 45% nitro solution... In his experience,
10% azeotrope kills an Al/Hg reaction... refluxs dies off..
Apart from the MeOH of the fuel, EtOH will be used as solvant, as this distills much more MeNH2... after reaction is done, 30% NaOH will be added
and alcohols distilled and neutralised with conc. HCl and evaporated to recover the HCl salt...
[Edited on 14-2-2007 by Klute]
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Sauron
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Yep, @Rosco, I agree, which was why I said I'd be disappointed with that yield. I started off my tenure as a RA doing Al/Hg reductions in anhydr EtOH
back in the Middle Ages, c.1975, before moving on to LAH/TiCl3 in THF (McMurry's Reagent) and the yields were much better. I'd be surprised if a whole
shelf of reducing agent options wouldn;t work and work well. Al amalgam is perhaps more kitchen friendly than most...if one were crazy enough to work
with HgCl2 in the kitchen.
Bottom line, it shouldn't be hard to find a quantitative prep from MeNO2 in the lit. If you're going to use a valuable reagent to make a somewhat
less valuable one, best be efficient about it.
Personally I still think one of the more direct approaches makes more sense as it is not that hard to seperate out (Me2)NH2 even by iterative
processes. If rigorously pure MeNH2 is reqd, and I don't know why it would be, then it is time for HPLC prep scale 20 g sample size and a few thousand
t.p. seperation in an hour or so. Crank up the old Waters 4000 and Millenium32.
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not_important
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Note that the Hofmann route has an alternative method, where the amide is reacted with bromine and then with concentrated aquous base. This gives a
much more concentrated solution. Chlorine could be used instead of bromine, but is harder to deal with.
If you'ev cheap acid, HCl or H2SO4, then you could neutralise the reaction mix, concentrate or even evaportate it, then add enough concentrate aqueous
NaOH to liberate the amine whic you distill off. If you use HCl, you could extract the amine hydrochloride with hot alcohol, as the inorganic produces
have low solubilites in alcohols. The amine sulfates have lower solubilities in alcohol and do not extract as well - need a proper extractor to do the
job.
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Furch
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As I mentioned in the post where I claimed success with the Fe/HCl reducing system on nitromethane, I was nowhere near as thorough in my workup as I
am today. I also wasn't as experienced nor as knowledgable (no hubris intended) as I am today. That experiment was merely intended to prove to myself
that it was possible to reduce aliphatic nitro compounds with iron in acidic media, and I didn't even follow up on it to optimize the procedure. I see
no reason whatsoever why the procedure, if performed correctly, would not give a quantitative yield.
So, to conclude, on my part, 50% was the yield I got on that particular occasion... That doesn't mean the ultimate yield for the procedure is 50%.
Al/Hg is a given if you ask me... You can't fail. Superior to the Fe/HCl in many ways, except for the mercury of course...
Peace out.
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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Organikum
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We had something here:
http://www.sciencemadness.org/talk/viewthread.php?tid=1261#p...
Some old textbooks tell that extraction with 95% EtOH is enough to yield MeAm of 98%+ purity, so I wouldnt really worry about some water in a IPA
extraction.
Methylamine crystals from alcohol just look completely different then ammonium chloride (see picture in the linked thread). So just forget everything
what looks like a white powder.
There was a funny "synthesis" of MeAm from formalin and ammonium chloride on Rhodiums page where large amounts of ammonium chloride were depicted as
"pure methylamine.HCl" - a good laugh. Had many pictures though and impressed for sure many. And mislead them nicely. Shows that this page wasnt such
a bummer and that Rhodium was anything but a good chemist - more an adolescent flaming Eleusis who was in jail and couldnt even respond anymore.
btw. did you know that Rhodiums real name was posted on ADC (dunno if its still there), when talk was about Strikes trial? XXX from Sweden?
And somewhere there was even Osmiums real name and email once, where was this?
Did I mention lately that I still miss a COMPLETE hive archive? With MaDMAx´s posts and those of some others which were stolen already before it went
down?
If it wasnt for PolySAM´s madness I would have exposed them thieves a long time ago.
And: Extraction of MeAm.HCl from a heap of ammonium chloride is a bitch, preseparation by crystallisation is a good idea, the textbooks and articles
didnt make this up for fun....
[Edited on 15-2-2007 by Organikum]
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Furch
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Organikum, why would you go and post something like that? Just because someone has done something less ethical on the Internet, which would in this
case at most result in an insult to another person on the Internet, that doesn't justify that you try and contribute to exposing their real life
identities. That is weak.
On the other notice, what do you mean when you say that extraction of methylamine*HCl from a heap of ammonium chloride is a bitch, when you earlier in
your post state that 98% purity can be obtained from simple recrystallization from EtOH, and even better from IPA (which is of course true)?
Someone on this forum tried to recrystallize ammonium chloride from boiling EtOH and got 0.6 g upon cooling, from what I think was 100 ml EtOH, and
when repeating the whole thing with 100 ml boiling IPA, he got no crystalls precipitated at all. That's good, yet old news! :-)
\"Those who say do not know, those who know do not say.\" -Lao Tzu
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