Coacervate Droplet Posted October 14, 2018 Share Posted October 14, 2018 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 Link to comment Share on other sites More sharing options...
John Cuthber Posted October 14, 2018 Share Posted October 14, 2018 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 1 Link to comment Share on other sites More sharing options...
Coacervate Droplet Posted October 30, 2018 Author Share Posted October 30, 2018 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. 2 Link to comment Share on other sites More sharing options...
Endy0816 Posted October 30, 2018 Share Posted October 30, 2018 Huh. Would see this cleaning up monoethanolamine around the CO2 Scrubers. Always wondered why it ended up brown. +1 Link to comment Share on other sites More sharing options...
Sensei Posted October 30, 2018 Share Posted October 30, 2018 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) Link to comment Share on other sites More sharing options...
Endy0816 Posted October 30, 2018 Share Posted October 30, 2018 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. Link to comment Share on other sites More sharing options...
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