Chem 3106-341 Lab 5 - Lab Report With Summaries And Solutions PDF

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Heather Holtrop Lab Partner- Jali Greene 2/28/17, CHEM 3106-341 TA- Yangxue Liu Friedel-Crafts Acylation: Acetylferrocene and Diacetylferrocene

PURPOSE: The purpose of this lab is to show the conditions at which the Friedel – Crafts Acylation is carried out. This reaction is an example of electrophilic substitution on an aromatic ring contained in an organometallic compound. REACTION:

SAFETY: Aluminum chloride: Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion. Hazardous in case of skin contact (corrosive), of eye contact (corrosive). Liquid or spray mist may produce tissue damage particularly on mucous membranes of eyes, mouth and respiratory tract. Skin contact may produce burns. Inhalation of the spray mist may produce severe irritation of respiratory tract, characterized by coughing, choking, or shortness of breath. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering. Acetyl Chloride: Very hazardous in case of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (irritant, permeator). Corrosive to skin and eyes on contact. Liquid or spray mist may produce tissue damage particularly on mucous membranes of eyes,

mouth and respiratory tract. Skin contact may produce burns. Inhalation of the spray mist may produce severe irritation of respiratory tract, characterized by coughing, choking, or shortness of breath. Inflammation of the eye is characterized by redness, watering, and itching. Ferrocene: Very hazardous in case of ingestion. Hazardous in case of skin contact (irritant), of eye contact (irritant), of inhalation. Methylene Chloride: Very hazardous in case of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (irritant, permeator). Inflammation of the eye is characterized by redness, watering, and itching.

PHYSICAL PROPERTIES TABLE: Compoun

MW

Amount

mmol

Mp(°C)

133.34

150 mg

1.12

190

78.50

80 µL

1.12

186.04

100 mg

0.54

Bp(°C)

d

nD

51

1.11

1.3898

d Aluminum Chloride Acetyl Chloride Ferrocene Methylene

173

4.0 mL

40

Chloride

PROCEDURE: Lab Period 1 1. Equip a 5.0 mL conical vial containing a magnetic spin vane with a calcium chloride drying tube attached to a Claisen head. 2. Add 2.5 mL of methylene chloride to the reaction vial. 3. Under the hood, add 80 µL of acetyl chloride while swirling. 4. Prepare a solution of 100 mg ferrocene in 1.5 mL of methylene chloride and use a syringe to add this solution to the resulting mixture.

5. Make sure conical vial is capped between each addition of every reagent. 6. The reaction at this point should be a deep-violet color. 7. Allow the reaction to proceed at room temperature for 15 minutes. TLC Sample Instructions 1. Obtain an aliquot for TLC analysis by removing a small amount of the reaction mixture by touching a Pasteur pipet to the top of the solution. 2. Dissolve this aliquot in 10 drops of cold methylene chloride and cap this to save is for TLC analysis. Isolation of Product 1. Transfer the reaction to a 15 mL capped centrifuge tube containing 5.0 mL of ice water. 2. Cool the tube in an ice bath and use drop wise addition of about 0.25 mL of 25% aqueous sodium hydroxide. 3. Extract mixture with three 3 mL portions of methylene chloride. 4. Cap, shake, and vent after each addition of the methylene chloride. 5. Remove the lower layer using a Pasteur pipet. 6. Combine the extracted portions into a 25 mL Erlenmeyer flask and dry the solution using anhydrous magnesium sulfate for 20 minutes. 7. Transfer the dried solution to a 10 mL Erlenmeyer flask in 4 mL portions. 8. Under the hood, concentrate the solution on a hot plate and steam of air to about 0.5 mL solution. 9. Remove several drops of the solution and add 10 drops of cold methylene chloride. Save this vial for TLC analysis. 10. Remove the remaining solvent under the hood to yield the solid product. Thin-Layer Chromatographic Analysis 1. Use TLC to analyze the two solutions saved previously in the lab. 2. Use previously developed TLC plates to determine the appropriate elution solvent required for separation of the mixture. OBSERVATIONS/ DATA:



We washed our product with methylene chloride



Our final product was orange



Drying our product took about 10 minutes

CALCULATIONS/ RESULTS: Percent yield=

0.2mmol 1−acetylferrocene x 100=74 % yield 0.269 mmol ferrocene

Actual yield= 0.2 g of product Theoretical yield= (228.07 g 1−acetylferrocene ) + (270.10 g 1,1−diacetylferrocene ) x 0.00054 mol=0.268 g of CONCLUSION: The lab was successful in converting ferrocene to 1-acetylferrocene and 1,1’diacetylferrocene via electrophilic aromatic substitution in a Friedel-Crafts acylation reaction. Aluminum chloride, dichloromethane, acetyl chloride, and ferrocene were mixed and reacted. Friedel-Crafts acylation acts as an acid-base reaction in the formation of the electrophile where aluminum chloride is a Lewis acid and acetyl chloride acts as a Lewis base. After the formation of the electrophile, it reacts with one of the benzene rings in ferrocene which helps to carry out electrophilic aromatic substitution of a hydrogen with an acetyl group.

POST LAB: 1. Acetyl chloride is hydrolyzed into acetic acid and HCl. Aluminum chloride hydrolyses in water, and this forms a mist when it comes in contact with air because hydrochloric acid drops form when it reacts with water vapor. This is the reasoning behind limiting exposure to water vapor in the air. 2. Ferrocene should travel almost to the top with the solvent because it is the least polar, and only reacts with the solvent. The mono-substituted product should have a higher Rf value due to it only having one group of substitution. It is less polar and will not react as

strongly will the silica gel of the TLC plate. The silica gel is polar and will not allow the di-substituted to travel as far up the TLC plate. 3. Different solvents must be used in this experiment to separate the products that have different polarities. For example, a nonpolar solvent is used to separate out the ferrocene. A slightly more polar solvent mixture for the mono-substituted product. Finally, a highly polar solvent mixture is used for the di-substituted product. Solvent mixtures must be used in order to gradually increase the polarity in order to correctly separate the mono an di-substituted ferrocene....