I did N-alkylation of a substrate by using K2CO3, 2-ethylhexyl bromide in DMF. After purification by column chromatography I got a liquid product. The problem is the presence of 2-ethylhexyl bromide as per proton-NMR. How can I remove it? I tried to dry the sample by vacuum, but it is not going completely.
Perhaps you are using the wrong solvent system for CTG. Draw the reaction equation and will try to help
Depending on the scale you are working on you could use triphenyl phosphine which is supported on polystyrene.
U can put another reaction with the mixture to make a very polar n-alkylated product so that ur expected prodduct will be unreacted and separate it by column chromatography..
The eluted fraction contains ur target material (TM)+ethylhexylbromide (right?)...so u can put a reaction taking that fraction to convert the residual 2-ethylhexylbromide in to another different n-alkylated prodcuct which is polar compared to ur TM..then do a colum to separate ur TM....
What about using a ion exchange resin, use a anion exchnager which has weak basic groups such as amine groups. I would soak the resin in methanol and wash the water out of it, then apply the mixture of your product and the alkyl bromide to the resin. Leave it to react and then wash off the product using methanol. I would hope that the alkyl halide would stick to the resin.
If your product is stable to heat then do a high vacuum distillation to remove the excess 2-ethylhexylbromide. find the bp at atmospheric pressure and deduce from there -depending on what pressure you can reach with your pump- the bp at the pressure you will perform your distillation. would be good to check the physical data for your product too.
Have you tried following completion of reaction, the reaction mixture to filter with a suitable amount of charcoal?
I doubt if charcoal will remove the alkyl halide, I know that normal charcoal has very little affinity for methyl bromide or another similar alphatic halide. Charcoal works best for polycyclic aromatic things, in some ways charcoal is the ultimate PAH as it is masses of benzene rings fused together.
Good to see someone from Masaryk University, back in 1999 I worked there for some time. I was in Josef Novosad's group then working in the same lab as Marek Necas.
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