Separation of Ferrocene and Acetylferrocene by Chromatography

Purpose

1. To prepare a dry-packed sample of product mixture of ferrocene and Acetylferrocene

2. To separate and purify the components in the product mixture by column chromatography.

3. To check the purity of the components by thin-layer chromatography (TLC).

4. To calculate the yield of acetylferrocene and the percent recovery of unreacted ferrocene.

Table of Quantity showing various physical properties

Type of substance Molecular Formula Molecular Weight (g/mol) Density(g/cm3) M.P.(oC) B.P.(oC) Solubility

Ferrocene C10H10Fe 186.03 1.49 172 oC-174 oC 249oC Insoluble in water, soluble in organic solvent

Acetyl-ferrocene C12H12FeO 228.08 - 81 oC -83 oC 161 oC - 163 oC (at 4 mm) Very slightly soluble in water, soluble in organic solvent

Ethyl Acetate C4H8O2 88.11 0.897 -83.6 oC 77.1 oC Slightly soluble in water (~8.3g/100mL, 20 oC), very miscible with alcohol, ether, acetone, benzene.

Hexane C6H14 86.18 0.6548 -95 oC 69oC Immiscible with water

Dichloro-methane CH2Cl2 84.93 -97 oC 40 oC 1.325 Slightly soluble in water (~1.3g/100mL, 20 oC), very miscible with most organic solvent.

Hazard

1. Ferrocene is highly flammable and it is harmful if swallowed.

2. Acetylferrocene is highly toxic if swallowed.

3. Ethyl acetate is irritant and flammable.

4. Dichloromethane is a suspected carcinogen.

Procedure

1. The mass of the product mixture was measured.

2. About 2mL of CH2Cl2 was added to the product mixture in a 30mL beaker and about 300mg of silica gel was added

3. The beaker was covered with aluminum foil with a hole and was CH2Cl2 was evaporated.

4. 2.3g of fresh silica gel was mixed with 7mL of hexane in a 30mL beaker to get a slurry.

5. Stirred the slurry constantly with hexane added and poured it into the column.

6. Hexane was added and run until the solvent was about 1cm above the silica gel.

7. About 1cm of sand was added followed by loading of the dried sample.

8. Hexane was added and run until the first fraction was collected in a 10mL Erlenmeyer flask.

9. The solvent was changed to 20% ethyl acetate-hexane mix and run until the second fraction was collected in another 10mL Erlenmeyer flask.

10. After the 2 fractions were collected, thin-layer chromatography was carried out using 10% ethyl acetate-hexane mix to analyze the fractions with comparison to standard ferrocene and acetylferrocene.

Observations

When the silica gel was dissolved in hexane, it formed cloudy slurry and showed a light grayish color. After the sample was loaded and the solvent began to run, there was a diffusion movement of colored sample molecules. The reddish brown color was more or less stationary while the orange color stopped moving very soon at the top of the silica gel, just below the reddish brown. The yellow color moved much faster than the orange and reddish brown, down the column.

After the solvent was changed from hexane to ethyl acetate-hexane mixture, the orange color began to diffuse down the column too while the reddish brown color remained stationary.

In analysis of the 2 colored fractions collected by TCL, it was observed that as the solvent ethyl acetate moved up, yellow spots appeared first. After sometime when the yellow spot was at the middle of the plate, the orange spots appeared. At the end, 2 yellows spots were at the upper section of the plate and the 2 orange spots were at the lower section of the plate. At the origin, there were no colored spots.

After vacuum evaporation of the 2 fractions collected, yellow powder-like substance was found covering the inner wall of one of the Erlenmeyer flask while orange crystalline substance was found at the other. The orange crystals were larger and more discrete than the yellow powders.

Data and Calculations:

Mass of crude product mixture =0.0936 g

Mass of Erlenmeyer flask (for ferrocene) = 49.9674 g

Mass of Erlenmeyer flask (for acetylferrocene) = 50.7664 g

Mass of flask and recovered ferrocene = 50.0425 g

Mass of flask and acetylferrocene = 50.7983 g

Amount of ferrocene recovered = 50.0425 - 49.9674 = 0.0751g

Amount of acetylferrocene obtained = 50.7983 - 50.7664= 0.0319 g

Percentage recovery of ferrocene = (0.0751g/0.0936 g)(100) = 80.2%

Percentage yield of acetylferrocene=(0.0319g/0.0936 g)(100) = 34.1%

Table one showing the Retention factor of unknown fractions with comparison to standard values

Chemical Compounds Distance from baseline to spots (cm)/Distance from baseline to solvent front (cm) Retention FactorRf

Standard ferrocene 3.5/4.2 0.83

Fraction #1 (yellow) 3.5/4.2 0.83

Standard acetylferrocene 1/4.2 0.24

Fraction #2 (orange) 1/4.2 0.24

Conclusions and Answers to Questions

Separation by column chromatography

Chromatography was commonly used as a purifying technique. The eluting solvent passed down the column by the gravity and an equilibrium was established between the solute absorbed by the absorbent (silica gel in this experiment) and the eluting solving flowing down. Since the components in the sample had different polarity and they interacted with the stationary phase and the mobile phase differently, the components would be carried by the solvent to a different extent and a separation of the components could be achieved.