Abstract

The purpose of this experiment is to separate the components of a mixture using column chromatography. The sample is a 50:50 mixture of ferrocene and acetylferrocene. Two fractions will be collected from the column separation of the mixture. Ferrocene (fraction 1) is eluted first using hexanes and appears as a yellow band in the column. Acetylferrocene (fraction 2) is eluted next using a 50:50 mixture of hexanes and diethyl ether solution.

Introduction

Column chromatography is one of many basic laboratory techniques taught in organic chemistry. It has widespread application in the organic synthetic lab because of its efficiency for separating and purifying components of a mixture. It can be applied to both liquid and solid samples, and multi-component mixtures. On a small scale, column chromatography is fast and cost effective. It is particularly useful for separating reaction mixtures containing reactants, products and byproducts.

Chromatography takes advantage of the differences in polarity and binding strength that the components of a mixture have for column adsorbents. Adsorbents are high surface area stationary phase materials that bind solute molecules. A mobile phase solvent, or eluent, is used to desorb solute molecules, carrying them along the column to a receiving flask. As the solvent polarity is increased, polar molecules bound more strongly to the column begin to solubilize and are carried down the column in the mobile phase. Equilibrium is established between binding to the stationary phase and solubility in the mobile phase. As the solvent polarity increases, more tightly bound polar molecules, firmly held by the adsorbent, establish equilibrium with the eluting solvent and flow along the column. This process is analogous to thin layer chromatography (TLC), gas chromatography (GC) and high-performance liquid-phase chromatography (HPLC).

About the author

Dean Antic, Ph.D., is a Senior NMR Applications Scientist, organic chemist and spectroscopist at Thermo Fisher Scientific, San Diego, CA. Formerly, Dean was an adjunct professor of chemistry at Northeastern Illinois University and a certified 9-12 chemistry instructor.

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