Separation of Secondary Amine and Tertiary amine

[KevinBe]

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%, 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...

Thank you

Kevin

[Mark Tracy]

Is recovery in the form of an acetate salt acceptable? Use 5% acetic acid to elute the secondary amine.

[KevinBe]

yes of course it's acceptable! Elution of an acetate salt is easier ?

[Mark Tracy]

Yes. Acidic conditions protonate the silica gel, and the amine no longer binds by ion exchange. The acetate salt will be less soluble in non-polar solvents, so you might need more ether and less hydrocarbon to keep it dissolved, or try (m)ethyl acetate.

[pve]

I don't what R means, but if your products are volatiles, you can use Gas Chromatography. There're are colunms designed for the separation of amines.

[tom jupille]

pve: I really doubt that KevinBE would want to do prep GC on 20g samples