Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: faust on January 24, 2006, 01:51:12 PM
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Hello,
I'm trying to do an effective separation of these two compounds :
R=EtOOC-CH2-CH2-
secondary amine : R-NH-CH2-CH=CH2 (the more polar)
Tertiary amine : R-N(R)-CH2-CH=CH2 (the less polar).
I'm trying every kind of eluant on my big colum chromatography (i'm working on 20 grams of product).
The tertiary amine comes out of the column really fast by using : Et2O/Petroleum ether 1:1
But it's a nightmare fore the secondary amine... I've tryed : Ether+5% Et3N and I've got five liters of solvant to evaporate!!!
And I tryed MeOH + 5%Et3N, and I got 3 liters... And I spent the all day for this purification...
Is there a trick or something for secondary amine? I'm really a newbie with amine purification...
Someone suggested me to add 5% of AcOH to my eluant in order to elute the acetate salt. But I haven't tried it yet.
Thank you
Kevin
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Eluting the acetate salt will be a disaster unless you are using reverse phase silica gel!
Try something like 10:1 dichloromethane:MeOH with 1% TEA. You can also try chloroform instead of dichloromethane. I would try to get away from pentane and probably even hexane because they won't help you much. Have you tried ethyl acetate already? You can also try adding a small amount of ammonium hydroxide instead of TEA.
There are some really crazy mixtures out there for really, really polar compouds, but you shouldn't need that.