Question

devise a way to separate alcohol from ester using column chromatography.

Please describe the general procedure. A few sentences are enough.

Answer 1

Separation of components from the mixture can be done either by distillation based on difference in the boiling point or by column chromatography based on the difference in the polarity of the component. Some compounds are polar, some are non- polar and some are partial polar. In the column chromatography, the mixture which is already present in the column along with sillica and hexane as usual solvent. Now the polarity of the solvent(hexane) will be change by adding the small % of polar solvent. Now the component of the mixture will be run downward comparatively from each other as cause of difference in polarity with solvent. So more polar component will come first with solvent and then can be collected and separated. So coming to our question as alcohol is more polar than ester due to more participation in hydrogen bonding while ester do have polar bonds but don't capable of hydrogen bonding. Now add prepared sillica(small amount) with hexane into column upto half mark then add mixture containing ester and alcohol. Now increase the polarity of solvent by taking 10% (approaximate)solution (ethyl acetate in hexane)and run the solution and you will see alcohol will come first out of the column while ester stays inside the column. Actually how exactly the polarity of solvent should be change determine by doing thin layer chromatography. This is just done to know the pre-requisite nature of polarity difference of our mixture