Freidel Crafts Acylation of Ferrocene LAB PDF

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Organic chemistry I lab report...

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Karla Gonzales CHEM 3220.303 Friedel-Crafts Acylation of Ferrocene 10/14/2013

Summary: In this experiment, we are synthesizing acetylferrocene from ferrocene. Then, we are purifying the product by column chromatography. Ferrocene is made up of two cyclopentadienyl anions and Fe2+. The cyclopentadienyl anion is a super aromatic when compared to benzene because of its high electron density and negative charge. We are reacting ferrocene with acetyl anhydride but the active electrophile is the acylium ion. This is an electron withdrawing group so we can expect for it to attach to the meta position. Molar Mass (g/mol) 186.04

Melting Point (°C) 172.5

Boiling Point (°C) 249

102.09

-73

139.8

Phosphoric acid

97.99

42.35

158

Acetylferrocene

228.07

81

161

Compound Ferrocene

Structure

Acetic anhydride

Acylium ion

Procedure: Synthesis of Acetylferrocene 1. 2. 3. 4. 5. 6. 7. 8. 9.

Add 93 mg of dry ferrocene to reaction tube Add .35 mL of acetic anhydride Add .1 mL phosphoric acid Cap the tube Warm in steam bath, while agitating mixture Heat an additional 10 mins. Cool in ice Add .5 mL of ice water drop wise Add drop wise sodium hydroxide until solution is neutral a. Test with indicator paper

Karla Gonzales CHEM 3220.303 Friedel-Crafts Acylation of Ferrocene 10/14/2013 10. Collect product on Hirsch funnel 11. Wash out with water Column Chromatography 1. 2. 3. 4.

5. 6.

7. 8.

9. 10. 11. 12.

Add 90 mg of a 50:50 acetylferrocene/ferrocene mixture Add hexanes Open the valve, elute the compounds Elution a. Ferrocene is eluted first, seen as a yellow band b. Collect in 10 mL flask Add 50:50 mixture of hexanes and ether Elution a. Acetylferrocene is eluted, seen as an orange band b. Collect in 10 mL flask Spot TLC plate with both solutions Evaporate solvents from flasks a. Place in tared 25 mL flask b. Heat flask in had while swirling contents Weigh residues Recrystallize products Determine weight and melting points Percent recovery based on 45 mg of each in original mixture

Pre Lab Questions: 1. Predict the order of elution of a mixture of triphenylmethanol, biphenyl, benzoic acid, and methyl benzoate from an alumina column. a. Starting with the compound that eludes the fastest, the order is biphenyl, methyl benzoate, triphenylmethanol, benzoic acid. 2. Once the chromatography column has been prepared, why is it important to allow the level of the liquid in the column to drop to the level of the alumina before applying the solution of the compound to be separated? a. It is important because you don’t want the liquid and solution to get mixed together because that would lead to skewed results. 3. A chemist started to carry out column chromatography on a Friday afternoon, reached the point at which the two compounds being separated were about ¾ of the way down the column, and then returned on Monday to find that the compounds came off the column as a mixture. Speculate the reason for this. a. The compounds could have merged together because the chemist was not there to keep an eye on the chromatrography.

Karla Gonzales CHEM 3220.303 Friedel-Crafts Acylation of Ferrocene 10/14/2013 4. What is the structure of the intermediate species that attacks ferrocene to from acetylferrocene? What other organic molecule is formed? a. The intermediate species is the acylium ion, which leaves a protonated acetyl anhydride molecule to produce both the ion and acetic acid. 5.

Why does the second acetyl group enter the unoccupied ring to form diacetylferrocene? a. The second acetyl group enters the second ring because is still highly activated because of its negative charge and high electron density.

Observations and Results: 

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4 layers formed: o Bottom layer was orange o Layer above that was black o Layer above that was yellow o Top layer was clear but with a yellowish tint Measured out .092 g ferrocene TLC results: o Orange dot: 1.5 cm o Solvent: 4.7 cm  Rf= .32 o Yellow dot: 3.6 cm o Solvent: 4.8 cm  Rf= .75 o Orange dot was determined to be acetylferrocene o Yellow dot was determined to be ferrocene Column chromatography results: see figure 1

Figure 1: Column chromatography results

Conclusion: The goal of this experiment was to synthesize acetylferrocene from ferrocene by FriedelCrafts acylation. We performed a column chromatography on the product to separate the product from unreacted material and the diacetyl byproduct. Column chromatography is effective because it separates based on the differing polarities of the compounds. The most polar group is the diacetyl group, followed by the acetyl group, and then ferrocene. We observed the expected results, we synthesized a good amount of acetylferrocene because the orange band was prominent on the chromatography column.

Karla Gonzales CHEM 3220.303 Friedel-Crafts Acylation of Ferrocene 10/14/2013 Post Lab Questions: 1. Acetic anhydride is the excess reagent in this experiment. In what step of the work-up procedure is this excess reagent destroyed? What product is obtained after it is destroyed? a. Acetic anhydride is destroyed when sodium hydroxide is added. Acetylferrocene is obtained after it is destroyed. 2. Why can hexanes be used to elute the unreacted ferrocene? Why does acetylferrocene not move down the column along with ferrocene? a. Hexanes elute ferrocene because they are nonpolar and ferrocene is the least polar group out of acetyl and diacetyl ferrocene. Acetylferrocene does not move down the column because it is more polar. 3. If you wanted to modify the experimental procedure to synthesize diacetylferrocene, what changes might you consider? Consider each of the following: stoichiometry, reaction conditions, purification of final product by column chromatography. a. To synthesize diacetylferrocene I would use excess acetic anhydride. The second ring would still be activated so the excess anhydride would attach to the ring....