Column Chromatography Lab Report

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The purpose and goal of this experiment is to separate a mixture of fluorene and 9-fluorenone through the method of column chromatography, and then determine the purity of the isolated compounds through thin-layer chromatography (TLC), as well as melting point analysis. Through column chromatography, gravity is utilized to move the solvent and compounds down the column, where the changes in the solvent polarity assists in eluting the desired compounds to separate fractions. Each fraction solvents can then be evaporated to obtain the compounds of interest. Through TLC, a thin layer of polar and hydrophilic silica gel on an inert sheet is used to spot the sample on the bottom of the sheet and is then developed in a jar of eluent, where through …show more content…

A small piece of cotton is then put into the bottom of the column, along with a 0.5 cm thick layer of sand (put on top of the cotton). 20 mL of petroleum ether, and with a dry funnel on top of the column, 7 g of alumina (Aluminum Oxide) is put into the column. To ensure that no alumina adheres to the sides, a glass rod in a rubber stopper can be put to use through the gentle tapping of the column with it; in addition, additional petroleum ether can also be put to use by rinsing the inner walls of the column with it. To cover the alumina, another 0.5-1 cm layer of sand is put to use. For the solvent to drain into an Erlenmeyer flask, the stopcock is to be open until the solvent level exactly reaches the top of the alumina, where the stopcock is then immediately shut off in order to prevent air bubbles from developing in the solid support. To load the sample into the column bed, 0.5 mL of a pre-made solution, containing 200 mg of fluorine and 9-fluorenone, as well as 0.5 mL of petroleum ether is to be carefully put on top of the column bed with a Pasteur pipet. At this point, the stopcock is to be open again until the top of the liquid level is at the top of the alumina. Next, with 1 mL of petroleum ether, the addition and draining process is then done a total of three more times, where upon the third draining, 10 mL of petroleum ether is be put into to the top of the column bed and put to drain into a small beaker (label it “Fraction 1”). After every 2-3 mL, a watchglass is used to collect a drop of eluent to determine if all white solid has been eluted (there may be a need of 10-20 mL of petroleum ether). Once all eluted, another small beaker (label it “Fraction 2”) can replace the beaker for “Fraction 1.” In “Fraction 2,” 5 mL of petroleum ether is used to elute (stop when yellow band starts to elute), followed by a change of eluent to dichloromethane.

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