Question

1- Brief discussion of column chromatographic separation (solvent polarity, elution of compounds etc.)

2- Relationship between polarity and thin layer chromatography​.

Answer 1

One of the way by which organic compounds can be purified is by column chromatography. The column retains the unreacted compound (excess of starting material, impurities, catalyst) since each has different polarity. The compound which is highly polar is retained in the column and the compound which is non polar or less polar is eluted by the solvent and runs off the column. So solvent polarity is very important in column chromatography. If the solvent is more polar than your compound, the compound will not get eluted it will remain in the stationary phase. No elution will take place If the compound is more polar. Hence selecting a solvent based on polarity of compound is very important.

In Thin Layer Chromatography instead of silica and alumina, glass is used as an stationary phase. Here also the polarity of solvent should be carefully determined, as strong polar solvents will make the compound adsorbed quickly and strongly, then no elution might take place if its very polar. Its always better to start with a low polar solvent preferably a mixture of low polar solvents and elute the sample in TLC.

Similar to column, In TLC also polarity of compound is important. The solvent polarity must be determined according to compounds polarity.