ANDLOS - 5-1-2010 at 11:08
How to avoid tailing problem in TLC
My coumpound is diaminobenzoate ethyl ester
and cyclized to benzimidazole
I want to follow up the reaction by TLC
but there is problem of tailing
I use ethyl acetate and drops of acetic acid
Klute - 5-1-2010 at 11:17
Using a drop of ammonia or better triethylamine works for me. I ususally used DCM:MeOH 10:1 or higher adding some EtOAc when it's not polar enough,
something like DCM:AcOEt:MeOH 10:2:1 + a drop of Et3N works for most amines.
As you have a polar ester in your molecule, and two amino-, you'll need to use something pretty polar, perhaps 10:3 DCM:MeOH. You'll have a high Rf,
but you should get a decent seperation.
Good luck
medchem - 5-1-2010 at 18:01
I think in your case, the main reason for tailing is low solubility of your compound in the running solvent. So, you can try in more polar solvent
like MeOH/Dichlromethane. Plus you can add 1% glacial acetic acid for better result.
And pls once you check the TLC plate. You need to activate it before running by heating.
Sometime, you can experience the tailing due to bad tlc plate (moisture) and sample loading.
Hope it will work.
[Edited on 6-1-2010 by medchem]
ANDLOS - 6-1-2010 at 08:19
thanks alot the problem resolved when i add few drops of TEA
ANDLOS - 6-1-2010 at 09:35
only one question what is the best method for work up of armatic amine from its aromatic nitro precursor