Organic Chem Lab Thin Layer Chromatography

Separation of Compounds by Thin-Layer Chromatography

Lab Performed on 11/27/11

John Doe

Abstract:

A separation of biphenyl, benzhydrol, and benzophenone was performed to identify a suitable solvent. The separation was done by Thin-layer chromatography. By comparing Rf values for each chromatogram on silica gel plate, the data revealed that dichloromethane yielded the best separation of the compounds based on polarity.

Background:

The purpose of this experiment is to figure out a proper solvent that will be used to separate a mixture of biphenyl, benzhydrol, and benzophenone by thin-layer chromatography.

Chromatography is used extensively in organic chemistry laboratories for routine analysis. Thin layer chromatography or TLC can be used to determine the purity of a compound, analyze the composition of a mixture, or to measure the progress of a reaction. The components of a mixture are separated by using two phases that directly compete. The stationary phase and the mobile phase work in competition to help separate the compounds or components of a mixture, based on adsorption. In TLC, the stationary phase is a polar substance that has adsorptive properties, such as silica or alumina gel that is mounted on a thin plate of glass. The mobile phase is an organic solvent that moves up the plate by capillary action.

The mixture is dissolved in an appropriate solvent and then applied to the base of the plate by spotting with a capillary tube or pipette. A spot of the mixture is placed on the plate by directly touching the tip of the tube or pipette to a designated area. Some situations might call for more than one spot of the mixture in the same designated area.

Spotting refers to the act of touching the pipette or tube to an area on the origin on the plate. After the right amount of solvent has been added, the plate is allowed to air dry.

Once dry the plate is then placed inside a developing chamber which consists of a container with a small amount of a...