woelen
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Diethyl amine turning brown
I prepared some diethyl amine solution in water, appr. 30% HN(CH2CH3)2 by weight. The other 70% is pure distilled water. When I prepared the liquid,
it was a perfectly clear colorless solution. I transferred it into a thoroughly cleaned and rinsed glass bottle with a cap having a teflon liner. I
have done every effort I could to keep the material pure.
Already 24 hours after I bottled it, the liquid had a pale yellow color. Now, 6 days later, it is a liquid, looking like apple juice. It still has the
same smell as when I bottled it, but it turns darker slowly.
Is diethylamine unstable, when mixed with water? I wanted the pure aqueous solution for experimenting with coordination complex with transition
metals, but now the strong brown color makes it totally useless for that purpose  .
I also still have some pure diethyl amine without water mixed in. This liquid still is colorless. Both liquids are stored in the same glass bottles
(transparent Duran glass bottles, 250 ml with red cap and teflon liner).
Can someone explain to me what is happening?
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mnick12
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Well here it what wiki has to say, "As a liquid it has a dark brown color due to impurities, however when distilled it is colorless. "
-http://en.wikipedia.org/wiki/Diethylamine
I do not think it is anything to worry about, and if I remember correctly aniline has the same problem. It also tends to discolor during storage, and
if it is vital that you have clear diethylamine you could distill it though it may get kinda stinky in your lab.
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jon
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your neighbors may think your running whore house, careful!!!
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mr.crow
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Funniest comment on Science Madness
Double, double toil and trouble; Fire burn, and caldron bubble
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jon
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it happened to me well not exactly but handling so much methylamine i finally got a compliant i pointed to an ice chest and said oh i go fishing a lot
i need to clean that out.
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Pseudomonia
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The brown colouration shouldn't be problem, it's just due to small amounts of impurities.
Rather you then me when handling it though, I hate the smell of fish as it is!
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jon
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actually you get used to it don't even notice it.
but there neighbors do.
i recommend cordoning off the area, don the gas mask and turn on the ozone generator. that's how to keep nosy neighbors from taking notice of you.
also cetain pet odor removers can knock the lingering amine odors down.
[Edited on 25-6-2010 by jon]
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anotheronebitesthedust
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For long term storage you could convert to the HCl salt.
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woelen
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@jon: what are you talking about? Gas mask and ozone generator? Come on... Diethylamine is somewhat smelly, but not more so than plain ammonia. I can
handle it comfortably and do not really bother about the smell. Only if the concentration becomes somewhat high, it becomes pungent, just like ammonia
is pungent at too high concentrations. There are other chemicals which are much harder to handle. All those stories about extreme smell and nosy
neighbours are highly exaggerated. Only if you handle this stuff in liter quantities you have to take precautions, but working with a 30% solution on
a test tube scale is not problematic at all.
@anotheronebitesthedust: Actually I have converted some of the diethylamine to a salt, but I also want to keep some of it as free base, because that
makes experimenting with complexes more easy.
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anotheronebitesthedust
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Sounds like maybe it's sensitive to heat and light. Try keeping it in an amber bottle in cool temps. Other than that I dunno.
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Arrhenius
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All amine free bases are sensitive to oxygen, and turn brown over time due to the formation of N-oxides, nitroso compounds, etc. I've never stored
alkyl amine solutions in water, but I would suggest storing amines neat, and under inert gas if possible. Just prepare solutions right before you
need them. Neat diethylamine definitely will not turn brown over a few days. Remember, your eye is only a sensitive detector for impurities that
absorb visible light! A little color is probably nothing to worry about.
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Anders Hoveland
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Will diethylamine react with dilute H2O2 ?
What exactly is the product formed?
If (CH3CH2)2NOH is reacted with acidified permanganate, will I get (CH3CO)2NOH ?
This should hydrolyze in NH4OH.
(CH3CO)2NOH + 2 NH4OH --> 2NH4CO2CH3 + NH2OH
Also can you post you (CH3)2NH and (Et)2NH synthesis, or just give a quick description of how you made it?
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jon
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@woolen yes i was handling methyamine in several hundred gram quantities it got so bad everywhere i went people would cover thier noses.
i would have to explain that i just came from the redlight district believe me it sticks to you.
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Anders Hoveland
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[Edited on 8-7-2010 by Anders Hoveland]
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MagicJigPipe
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Most amines like this slowly turn brown over time. Aniline, pyrrole and triethylamine (just to name a few). I have seen a bottle of triethylamine
that was 50 years old and it had collected a lower layer of black viscous oil. The top layer, however, was still just a little brown so apparently it
gets saturated or something and starts settling at the bottom.
With pyrrole the darkening is due, at least in part, to polymerization. Light and exposure to O2 effects this. I distill and then immediately place
in a brown bottle, purge with N2 and place in the refrigerator. I use a septum/syringe to get it out.
Is this overkill?
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Anders Hoveland
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How could (Et)3N possibly get oxidized to polymerize?
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MagicJigPipe
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Are you suggesting that it is impossible to oxidize triethylamine??? I was simply suggesting that it could be similar to pyrrole, which certainly
does oxidize and polymerize "spontaneously" with the same visible results.
A quick search reveals nothing on the decomposition of triethylamine at room temperature. Can anyone offer any insight?
Although this takes place at 211*C and above, it is an interesting read. (split into two .RAR files b/c it is just over 2 MB)
Attachment: Gaseous Oxidation of Tertiary Aliphatic Amines. I. Triethylamine.part1.rar (1.1MB)
This file has been downloaded 648 times
Attachment: Gaseous Oxidation of Tertiary Aliphatic Amines. I. Triethylamine.part2.rar (1MB)
This file has been downloaded 535 times
[Edited on 7-9-2010 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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