Question

Thin layer chromatography in the organic chemistry typically uses a glass plate coated with silica gel, which serves as the stationary phase. The mobile phase in the experiment is an organic solvent or mixture of organic solvents. The mobile phase pulls the organic material(s) being analyzed up the plate by dissolving them in the solution. So, the more something dissolves in the mobile phase the further up the plate it moves. The mobile phase in this experiment will involve which materials?

Select one:

Hexanes and Ethyl Acetate

Silica Gel

Ethyl Alcohol

Water

Ethanol and Water

Water and Ethyl Acetate

Hexanes

Ethyl Acetate

This is a trick question because the mobile phase evaporates and is therefore not important.

Answer 1

As mentioned in the question, the thin layer chromatography (TLC) in the organic chemistry typically uses a glass plate coated with silica gel as the stationary phase and an organic solvent or mixture of organic solvents as the mobile phase. The mobile phase pulls the organic material(s) being analyzed, up the plate by dissolving them in the solution. So, the more something dissolves in the mobile phase, the further up the plate it moves.

In general, the mobile phase in the TLC experiment involves the use of a mixture of hexanes and ethyl acetate, their ratio depends on the nature of the organic material being analyzed.

Reason: If the organic material/compound being analyzed is the one with a long chain of carbons, i.e. less polar and more nonpolar, then you should prefer an eluent containing the mixture of hexane (nonpolar solvent) and ethyl acetate (polar solvent) with the major portion of hexane.

If the organic material/compound being analyzed is the one with polar functional groups and heteroatoms, i.e. less nonpolar and more polar, then you should prefer an eluent containing the mixture of hexane (nonpolar solvent) and ethyl acetate (polar solvent) with the major portion of ethyl acetate.