Question

1. rank the intermolecular interactions involved between each compound tested in the stationary or moving phases of TLC using silica gel.

Coumpond Intermolecular Forces Cumene LDF Acetanilide H bond, Dipole-dipole, LDF Phenyl methanol H bond, Dipole-dipole, LDF Benzoic acid H bond, Dipole-dipole, LDF Dipole-dipole interaction, LDF Acetophenome Methyl benzonate Dipole-dipole interaction, LDF

Answer 1

The strength of intermolecular forces is as follows:

Hydrogen bond > Dipole- Dipole > London dispersion forces

Since cumene is a non- polar compound, it involves only LDF and hence is the weakest interactions of all is present in cumene.

Acetanilide contains a NH group and a carbonyl group due to which it contains strongest H-bonds and other interactions.

Benzoic acid can form dimers which eventually results in strong intermolecular interactions as compared to phenyl methanol. Thus phenyl methanol has the weakest interactions among these three compounds.

Among acetophenone and methyl benzoate, acetophenone has stronger intermolecular interactions.

Therefore the rank of the compounds on the basis of intermolecular interactions among them in case of TLC follows the order:

Acetanilide > Benzoic acid > Phenyl methanol > Acetophenone > Methyl benzoate > Cumene.