My old bottle of ethanolamine has turned brown.  I wonder if anyone has some experience or suggestions with this.  I can get some fresh reagent but I was surprised that this has happened.  I suspect that it has been contaminated but I am pretty much the only chemist with access to that so I wonder if it has undergone some interesting reactions.  The bottle is over 10 years old.  Aldrich reagent grade

 

Oxidation by air is sufficient to get it to go brown.

You get formation of aldehydes and then reactions like this

https://en.wikipedia.org/wiki/Maillard_reaction

It's likely that the material is still fairly pure; the brown colour may be due to far less than 1%  of impurity.

And redistillation (under vacuum if you have that option) will probably clean it up

Thank you.  I was able to source a small condenser and will try to redistill.  No vacuum apparatus available here but I have learned more about proper storage.  The price on reagents is going up so fast it is wise to have some ability to purify the old stuff when practical.  I appreciate your response.  At least I know that it is not that unusual for this molecule to darken.  Maillard chemistry is very interesting.  The other suspect (in my mind) was the bottle of mercaptoethanol that sat next to it for years.  I suppose R-NH2 is the stronger nucleophile but I wonder if R-S(minus) might compete.  

I lurk the forum, really enjoy the high level of professionalism and openness.  

 

Huh. Would see this cleaning up  monoethanolamine around the CO2 Scrubers. Always wondered why it ended up brown. +1

40 minutes ago, Endy0816 said:

Huh. Would see this cleaning up  monoethanolamine around the CO2 Scrubers. Always wondered why it ended up brown. +1

"Stable under normal conditions but will absorb the moisture in the air and react with carbon dioxide to form salts. Decomposes when exposed to sunlight. Oxidizes slowly in air, turns yellow and then brown. This reaction will accelerate due to the presence of heat and metals."

(from Material Safety Data Sheet)

 

10 hours ago, Sensei said:

"Stable under normal conditions but will absorb the moisture in the air and react with carbon dioxide to form salts. Decomposes when exposed to sunlight. Oxidizes slowly in air, turns yellow and then brown. This reaction will accelerate due to the presence of heat and metals."

(from Material Safety Data Sheet)

Yeah we didn't really use our MSDS binder as often as we probably could have. It was on the bulky side but...

Generally relied on manuals and procedures instead.