Laboratory Report: Purification of Ferrocene and Acetyl Ferrocene through Column Chromatography

Column chromatography is a widely employed technique for the purification of individual compounds from mixtures, ensuring minimal cross-contamination. This method is particularly effective for solids or high-boiling liquids. In this lab, we focused on the separation of ferrocene and acetyl ferrocene, both complexes of an iron(II) cation and two aromatic, organic anions. Thin Layer Chromatography (TLC) was also introduced, a technique utilized for the separation of non-volatile mixtures.

Experiment:

1. Materials and Setup:
   • Unknown mixture of ferrocene and acetyl ferrocene.
   • Semimicroscale column.
   • Petroleum ether (30-40 mL) as the solvent.
   • Powdered adsorbent (alumina basic, 4.5g).
   • Sand and CH2Cl2 for rinsing.
   • 50/50 mixture of petroleum ether and diethyl for elution.
   • 50mL Erlenmeyer flasks with chips.
   • TLC plates, capillary, ethanol/toluene, and iodine chamber.
2. Procedure: a. Prepare a semimicroscale column. b. Fill the column with petroleum ether and alumina. c. Elute with petroleum ether until level with the top of the alumina. d. Add the weighed solid sample to the top of the column.
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   e. Rinse with CH2Cl2 if needed. f. Collect the yellow material in an Erlenmeyer flask. g. Elute acetyl ferrocene with a 50/50 mixture of petroleum ether and diethyl. h. Collect the liquid in a flask. i. Continue elution until the orange band is washed from the column. j. Spot TLC plates with ferrocene and acetyl ferrocene solutions. k. Put TLC strips in an ethanol/toluene jar, observe, and record. l. Place TLC strips into an iodine chamber and calculate RF value. m. Use a rotary machine to collect solid product.

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Results/Data:

1. Materials Used:
   • Alumina basic: 4.511 grams.
   • Petroleum ether: 30-40 mL.
   • Unknown number: 5.39.
   • Sand (estimated amount).
   • Erlenmeyer flask weight: 35.79 grams.
   • Round bottom flask weights: Ferrocene (31.331g) and Acetyl Ferrocene (32.840g).
2. Observations:
   • Ferrocene turned light orange with petroleum ether.
   • Acetyl ferrocene turned dark orange with a 50/50 mixture, indicating increased polarity.
   • Colors differed due to the polar nature of the elution solvent.
3. Yield:
   • Ferrocene collected: 1.0598 grams.
   • Acetyl ferrocene collected: 1.232 grams.

Calculations:

1. RF Value Calculation:
   • RF value = Distance traveled by the compound / Distance traveled by the solvent.
   • Measurements taken from TLC experiment.

Discussion:

Column chromatography proved successful in separating ferrocene and acetyl ferrocene. The difference in elution solvents led to distinct colors, aiding in the identification of compounds. The collected yields indicate the efficiency of the separation process.

Conclusion:

The experiment demonstrated the practical application of column chromatography in separating ferrocene and acetyl ferrocene. The obtained results, including calculated RF values and collected yields, contribute to a comprehensive understanding of the purification process.

This laboratory exercise enhances knowledge of chromatographic techniques, compound separation, and the impact of elution solvents on the outcome of the procedure. The combination of column chromatography and TLC provides a powerful tool for purification and analysis in chemical laboratories.

In the column chromatography process, where the mobile phase is a liquid and the stationary phase is solid, we collected liquid samples after elution. The weight of the collected liquid for ferrocene was 4.3975, and for acetyl ferrocene, it was also 4.3975. The subsequent use of a rotary machine efficiently removed solvents from the samples through evaporation. After the rotary machine, the remaining solid was weighed, resulting in 1.0598 for ferrocene and 1.232 for acetyl ferrocene. To evaluate the separation further, we calculated the Rf value using the formula Rf = distance spot moved / distance solvent moved.

In the TLC experiment, no orange spot was observed for ferrocene, but a green spot appeared towards the top of the strip. For acetyl ferrocene, there was an orange spot in the middle and a light green spot towards the top. The calculated Rf values for these spots indicated the degree of polarity. The Rf value for the green spot in ferrocene was 0.8mm, the orange spot was 0.4, and the green spot was 0.8mm. For acetyl ferrocene, the Rf values were 0.4 and 0.88mm for the orange and green spots, respectively. This suggests that acetyl ferrocene exhibits a higher degree of polarity.

In conclusion, the unknown number assigned was 5.39, and the results indicate that acetyl ferrocene is polar, evidenced by both orange and green spots in the TLC experiment. Ferrocene, being non-polar, only exhibited a green spot. The collected liquid weights (mobile phase) were 4.3975 for ferrocene and 2.9385 for acetyl ferrocene, while the remaining solid weights (stationary phase) were 1.0598 for ferrocene and 1.232 for acetyl ferrocene. Melting point range determination revealed 164-169 for ferrocene and 73-77 for acetyl ferrocene. It was concluded that methylene chloride played a crucial role in facilitating the separation of ferrocene and acetyl ferrocene.

Lab References:

• Chemistry 234 Lab Manual, San Francisco State University
• Methylene Chloride
• Alumina
• Ferrocene
• Petroleum Ether
• Acetyl Ferrocene