Question

Define the following terms and draw one example of each using organic molecules:

Van der Waal's non-polar interactions, Dipolar interactions, Hydrogen Bonding.

What is the function of the silica gel in TLC experiment?

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

Thank you so much!

Answer 1

Van der Waal's non-polar interactions Van der Waals forces include attractions and repulsions between atoms, molecules, and surfaces, as well as other intermolecular forces. They differ from covalent and ionic bonding in that they are caused by correlations in the fluctuating polarizations of nearby particles

ex : N_2, O₂

Dipolar interactions : Dipole-Dipole interactions occur between molecules that have permanent dipoles; these molecules are also referred to as polar molecules. ex- HCl

Hydrogen Bonding : A hydrogen bond is the electrostatic attraction between polar molecules that occurs when a hydrogen (H) atom bound to a highly electronegative atom such as nitrogen (N), oxygen (O) or fluorine (F) experiences attraction to some other nearby highly electronegative atom.

ex H2O, NH3..

The function of the silica gel in TLC experiment : silica gel is act as stationary phase which absorbs the compound and when passes mobile phase(solvent) on silica gel the compounds move forward based on their polarity so we can separate the reaction mixture to their respective products by pasing suitable mobile phase or solvent through silica gel.