lab report

PRE LAB REPORT
Reynaldo Riboul
TLC and Column Chromatography
October 6, 2013

Table of Chemicals:
Chemical
Hazards
Mol. Wt.
Density
Grams
Moles
Acetone
Flammable, Irritant
58.08 g mol−1
0.791 g cm−3
2.0 g
0.0344
Hexane
Flammable, Irritant, Dangerous to Environment
86.18 g mol−1
.6548 g mL−1
9.0 g
0.1044
Fluorene
Very toxic to aquatic life with long lasting effects
166.223 g/mol
1.202 g/mL
0.3 g
0.00180
Fluorenone
Irritant
180.20 g mol−1
1.13 g/cm3
0.3 g
0.00166
Alumina none 101.96 g mol−1
.95–4.1 g/cm3
1.25g
0.01225
Nitrogen (g)
Nitrogen is nontoxic, but may cause suffocation by displacing the oxygen in air.

28.02 g/mol
1.251 g/L
N/A
N/A

Procedure:

Obtain for dry test tubes and number them 1 through 4. Prepare two dry Pasteur pipets with bulbs attached. Place 9.0 mL of hexane, 2.0 ml of acetone, and 2.0 mL of solution of 70% hexane-30% acetone into separate Erlenmeyer flask. Label and stopper each flask. Place 0.3 mL of a solution containing fluorine and fluorenone into a small test tube. Stopper the test tube. Prepare one 10-cm x 4.3 cm TLC with four marks for spotting. Prepare four micropipets to spot the plates.

Prepare a chromatography column packed with alumina. Place a lose plug of cotton in a Pasteur pipet and push it gently into a position using a glass rod. Using a file, score the Pasteur pipet about 1 cm below the cotton plug. To break the tip off the pipet, put your thumbs together at the place that scored and push quickly with both thumbs.

Add 1.25 g of alumina to the pipet while tapping the column gently with your finger. When all the alumina has been added, tap the column with your finger for several seonds to ensure that the alumina is tightly packed. Clamp the colmn in a vertical position so that the bottom of the column is just above the height of the test tubes you will be using to collect the fractions. Place test tube 1 under the column.

Running the column. Using a Pasteur pipet, add 3 mL of hexane to the column. The column must be completely moistened by the solvent. Drain the excess hexane until the level of hexane reaches the top of the alumina. Once hexane has been added to the alumina, the top of the column must not be allowed to run dry.

When the level of the hexane reaches the top of the alumina, add the solution of fluorine and fluorenone tot eh column using a Pasteur pipet. Begin collecting the eluent in test tube 2. Just ass the solution penetrates the column; add 1 ml of hexane and drain until the surface of the liquid has reached the alumina. Add another 5mL of hexane. As fluorine elutes off the column, some solvent will evaporate, leaving solid fluorine on the tip of the pipet. Using a Pasteur pipet, dissolve this solid off the column with a few drops of acetone.

After you have added all the hexane, change to the more polar solvent (70% hexane-30% acetone). When changing solvents, do not add the new solvent until the last solvent has nearly penetrated the alumina. The yellow band (fluorenone) should now move down the column. Just before the yellow band reaches the bottom of the column, place test tube 3 under the column. When the eluent becomes colorless again, place test tube 4 under the column and stop the procedure.

Tube should contain fluorine and tube 3, fluorenone. Test the purities of these samples using the TLC. You must spot the solution fro tube 2 several times in order to apply enough sample on the plate to be able to see the spots. Using a warm water bath and a stream of nitrogen gas, evaporate the solvent from test tubes 2 and 3. As soon as all the solvent has evaporated from each of the tubes, remove them from the water bath. Determine the melting points of fluorene and fluorenone.