After esterification, excess long chain alcohol( octanol) still present. The alcohol need to be remove to get a pure ester. How to remove the excess alcohol as long chain alcohol does not soluble in water and boiling point of the alcohols are quite high.
How about destillation under reduced pressure? Or general fractional destillation under reduced pressure? But yeah, Michael Päch is right, the more information you are giving us the better the answers/solutions will be ;)
BW
There are two possibilities:
1) Reduce the equivalents of alcohol. e.g. If your molecule has 2 carboxylic acid functions use exactly the same equivalents (=2). Carry out the reaction in toluene. Workup by extraction with cold NaHCO3 or Na2CO3 solution
2) azeotropic removal or liquid-liquid extraction with 2 imisscible organic solvents
If you are making your ester in a few g scale or less column / flash chromatography could be tried to isolate your ester in pure form.
In case of relatively large scale synthesis, your best option would be to carry out a distillation under reduced pressure. If required, you may use a suitable column for achieving better separation.
Either distillation or using a sulfonylchloride resin to remove the excess of heavy alcohol. Using this resin can release HCl in the medium reaction and the ester function should be stable and could'nt be reduced with HCl.
Dear Ruwaida
In this case to minimise the quantity of alkohol, because your alkohol may boil quite closely to ester and even vacuum diatillation may be not effective and column chromatography is for little scale only, you have to change reaction conditions. Use a large exsess of organic acid to force ALL (or almost all) alkohol to react and during water workup wash your mixture with soda to remove the excess of acid. And NO chromatography and fracrional vacuum distillation - standard workrup only and almost pure ester!
thanks a lot for all the suggestions and comments! Really appreciate it. :)
I'm doing the esterification with octadeacanol. After the reaction i can not do column chromatography because my acid reactant is amino acid. I tried precipitation with acetone-HCl, still i'm unable to get rid of long chain alcohol. Can any body suggest me a better way to remove excess long chain alcohol?
Concentrate your reaction mixture then dissolve in Ethyl acetate and filter. Then wash this ethyl acetate layer with citric acid solution followed by saturated sodium bicarbonate solution twice. Dry the organic layer and go for column chromatography. now you will not face that problem.
All the best.
May I know what is the solvent used for the reaction?
I recommend vacuum destillation. Destillion under 1 atm isn't the best option.
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