Cloner
Hazard to Others
Posts: 150
Registered: 7-12-2004
Member Is Offline
Mood: apocalyptic
|
|
triethylamine
And out of the abandoned, forgotten basement I came again, with my recovered treasures. This time there is an old bottle of triethylamine which is
browny or reddish and producing white smoke. The person responsible for storing these chemicals a long time ago did well at his job some of the time,
as I have recovered loads of working sodium, LiAlH4 and TFAA. Yet, the TEA seems to be spoilt. It was stored over molsieves though, so there
can't be much water in it. It was stored in such a brown bottle, in an ever dark place only fit for torturing prisoners. What would be likely
degradation products of TEA?
[Edited on 18-1-2005 by Cloner]
|
|
|
Kinetic
Harmless
Posts: 45
Registered: 31-12-2004
Member Is Offline
Mood: fine
|
|
Triethylamine
It's quite strange that your triethylamine has decomposed under storage conditions which reactive compounds such as LAH, TFAA and sodium have
survived.
I checked the MSDS, which of course gives the worst case scenario of decomposition products. Unsurprisingly, it is stable under normal temperatures
and conditions. It could be that the molecular sieves have catalysed decomposition to whatever has caused the brownish colour (perhaps dissolved
nitrogen oxides, which can form according to the MSDS).
If I were you I would distill it from calcium hydride. If you don't have that, virtually any other drying agent could do the trick, for example
CaO, KOH, NaOH, LAH (since you have some) or maybe even sodium, since triethylamine doesn't have any acidic protons.
|
|
|
unionised
International Hazard
Posts: 5104
Registered: 1-11-2003
Location: UK
Member Is Offline
Mood: No Mood
|
|
What was the bottle's stopper made of?
It might be that the colour is due to leached stuff from the seal.
At any rate, a nice simple distillation will probably clean it up.
I don't think using LAH as a drying agent is a good idea, particularly when you don't know what impurities are present.
|
|
|
Cloner
Hazard to Others
Posts: 150
Registered: 7-12-2004
Member Is Offline
Mood: apocalyptic
|
|
The stopper is a glass one, I call it apothecary bottles. This should close well enough, although it was unwaxed. Would that be a cause? By the way
the bottle wasn't as old as some of the other stuff, couple of years I think.
nitrogen oxides require oxygen this is a reason for me to dismiss them as an option.
Distilling over a drying agent seems like a good plan, I have CaCl and P2O5 but for obvious reasons more readily spend my CaCl ...
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
The unknown product of reaction/decomposition of the triethylamine, if oxygen was present, could be the amine oxide, (CH3CH2)3NO, in which the N is
pentavalent and carries a positive charge, with a negative charge on the O. Amine oxides are usually formed by the reaction of tertiary amines (only)
with hydrogen peroxide or a peroxycarboxylic acid; traces of H2O2 are always present if both O2 and H2O are present.
Tertiary amine oxides, having at least one ethyl or longer group, in turn decompose with heat, optimally at 150ºC, to a dialkylhydroxylamine and an
alkene, in the Cope elimination; in this case:
(CH3CH2)3NO ---> CH2=CH2 + (CH3CH2)2NOH
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
