madscientist
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Reaction of CH3OH with NH3
Does anyone know for certain what happens? This is my current hypothesis:
CH3OH + NH3 ----> CH3NH2 + H2O
CH3NH2 + CH3OH ----> CH3NHCH3 + H2O
CH3NHCH3 + CH3OH ----> (CH3)3N + H2O
It could be easily tested by mixing an excess of CH3OH with NH3, because (CH3)3N should be extremely insoluble in any polar solvent.
I weep at the sight of flaming acetic anhydride.
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vulture
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You can't get amines from alcohols, only from halogenalkanes with NH3.
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PrimoPyro
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Uh not true.
You can too go from alcohol to amine. Its called the mitsunobu reaction IIRC.
And yes, this reaction between methanol and ammonia has been used before, but it requires very high pressure and high temperature too, and probably a
catalyst as well.
PrimoPyro
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kingspaz
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R-OH + NH3 ---> R-NH2 + H2O
the problem is that you get a mixture of primary secondary and tertiary amines. that is:
R-NH2, R-NH-R and R-N-N2
Al2O3 will catalyse this reaction. i didn't know Al2O3 did this but i remember reading it somewhere and i've just got the book out and found it. it
also says 'heated together under pressure with Al2O3'. the amines could be separated by fractional distillation i'd expect.
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PrimoPyro
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Ratios
That is why you use a higher ratio of ammonia to methanol to prevent secondary amines. Tertiary amines need more heat to form.
And the mitsunobu reaction doesn't produce secondary and tertiary amines IIRC.
PrimoPyro
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vulture
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Mitsunobu Reaction? Yeah right.....
The mitsunobu reaction is the condensation of alcohols with carbonic or similar acids with Triphenylphosphan or Diazendicarbonaciddiethylester to form
esters, peptides, etc.
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PrimoPyro
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Such Narrow Vision
Please look at
http://themerckindex.chemfinder.com/TheMerckIndex/NameReacti...
Use your alcohol as your substrate and the nucleophile is the amide ion. I did not say it was practical, I said it was possible. Now that I refer
back, I see that any amine can be produced if the conditions are right, but no runaway reactions will occur because new nucleophiles would need to be
generated from the formed amines to have multiple reactions of the same species occur.
This has been exploited before in P2Pol --> amphetamine type conversions.
PrimoPyro
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vulture
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Wow, sorry
whoops. Have to excuse myself here. I guess I was sleeping when I replied to this thread. This reaction seems blatently obvious now. Sorry primo.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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vulture
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I've found it...
The process is called ammonolysis and can be described by the following reaction scheme:
R-OH + NH3 -> R-NH2 + R2NH + R3N
-H2O
Like kingspaz mentioned, they must be separated by fractional destillation or extraction.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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acx01b
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i am nearly sure that you need catalyst (AlCl3 ?) and at least Heat to directly aminate an alcohol, specially a primary alcohol.
whereas to aminate an alkyl halide (alcohol + PCl5) with NH3 you just need to do it in Polar organic solvent.
(the alcohol non-chlorinated works as solvent)
it takes me back to an other question:
can I have NH3 dissolved in anything else than water ? (to do amination reactions you must use dry NH3)
for exemple: CaCl2 mixed with 30% Ammionia in water, Ammonia Gaz is formed, and collected to dissolve in ethanol ???
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Geomancer
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Actually, I too am looking for information on ammonia solubility, particularly in anhydrous isopropanol. Although, ammonia is listed as an
incompatable in the msds. Why?
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acx01b
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i founded that vwr sells some NH3 in ethanol 30%, so I think it is the easier way to get ethylamine from hexamine and HCL aq:
HCL aq + MgSO4 --> HCL gaz
collect it in some dried ethanol, you'll get C2H5Cl
in an other part, make some 10-20% ammonia in ethanol with hexamine + H2O + NaOH, collecting the NH3 gaz in some dried ethanol, and then add 1mL of
the 20% C2H5Cl in ethanol into 20mL of 20% NH3 in ethanol: you'll get a mix of NH3 and C2H5NH3 in ethanol, without diethylamine and triehylamine
and ammonium.
if someone know and other way, thisone looks quite easy and quite safe, as far as you dont need to heat at anytime, but maybe i'm wrong....
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xxxxx
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nh3 in alcohol
an easy way to obtain nh3 in alcohol is to take a 500 ml jar of 28% nhoh4 and a 500 ml jar of alcohol and place them together in a 4000 ml jar with a
lid. after about a day or two the ammonia vapor will go into the alcohol in about 15%, which is about the saturation point for ammonia in ethanol.
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antibond
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amines
the monomethylamine of commerce is typically made using MeOH and NH3 under pressure and at about 400-500C using a catalsyt (typically alumino
silicates, zeolites etc) in a tube furnace. Dimethylamine and trimethylamine are also produced in the reaction typically. Supressing the formation
of the undesired amines results in a very low conversion of the NH3 MeOH mix (unfavorable equlibrium). Threre are however some interesting variations
of the alkylating reaction producing monomethylamine in decent yield (40% or so if I recall-as compared to di and tri production) and with good
conversion of the starting reactants. This info. however is based on patents and not scientific literature which translates to less reliable. I f
the info. were good however, and even if the NH3 was not completely converted, perhaps the NH3 gas and monomethylaine gas could be fractionated under
pressure to obtain the methylamine relatively pure. I believe the boiling points of NH3 and mono amine are far enough apart that it might work w/o
too big a column. Will dig up more specific info. on the conv. percentages etc. Any thoughts?
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