We used Chloroform:Isopropyl alcohol and Ethyl acetate:Acetic acid for solvents

Question

We used Chloroform:Isopropyl alcohol and Ethyl acetate:Acetic acid for solvents in TLC lab to get Rf values of aspirin and ibuprofen. What difference does it make trend wise? Also explain the observed trend in terms of the chemical structure and molecular interactions involeved between the analyte, solid phase and the mobile phase.

These are the results I got.

Chloroform:Isopropyl alcohol --> Rf of Aspirin=0.68 and Ibuprofen=0.78

Ethyl acetate:acetic acid --> Rf of Aspirin=0.79 and Ibuprofen=0.85

Explanation / Answer

Polar molecules are attracted by polar molecule. Non polar molecule are attracted by Non polar solvent. Like dissolves like.

Chloroform is a solvent which is non polar but Isopropyl alcohol is polar. So interaction between them is weak and hence Isopropyl alcohol travells faster and more distance. Isopropyl alcohol is not attracted by chloroform.

Ethyl acetate and acetic acid are both polar and are attracted by large force og hydrogen bonding. Due to this solid molecule is not able to move faster and observed Rf value will be small

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