Synth of adipic acid - Lab report PDF

Preview

Summary

Lab report...

Description

6th July, 2021

Page 1 of 6 Oxidative cleavage: Synth of Adipic Acid

Objective: To synthesize adipic acid by oxidative cleavage of the C=C bond in cyclohexene Introduction: In this lab experiment, we synthesize a dicarboxylic acid from an alkene. The reaction involves oxidative cleavage of the double bond of the alkene. Adipic acid has many commercial uses. Some of these are, it is used as an additive to drinks, food flavorings, and is used in synthesis of nylon-6,6. Nylon 6-6 is used in manufacture of many other products like upholstery, carpet fibers, clothing, tire reinforcements and auto parts. The oxidative cleavage of alkenes is done with hydrogen peroxide. This is because hydrogen peroxide is a greener oxidant for this reaction and produces water. Other compounds like potassium permanganate produce large quantities of hazardous MnO2 waste.This can contaminate the environment. The equation below shows the reaction between cyclohexene and hydrogen peroxide as an oxidizer with the use of catalyst which produces adipic acid and water. Equations:

Physical Constants and Safety hazards: Literature melting point of Adipic acid is below 151-153 degrees celsius. Be careful with the phase transfer catalyst as it can transport contaminants to the skin. Avoid getting hydrogen peroxide on your skin and clothing as it burns skin.

Procedure and observations: Procedure

Observations

Obtain a 50 mL round-bottom flask with a stir bar. Add 0.50g of sodium tungstate dihydrate. Add 0.50g of Aliquat 3363 Add 11.98g of 30% hydrogen peroxide.

Avoid getting it on your skin.

Add 2.00g of cyclohexene.

Stir it.

6th July, 2021

Page 2 of 6 Procedure

Fit the round bottom flask with 14/20 joint water cooled condenser.

Observations Water in the bottom and out the top

Heat the mixture. Set the rheostat to 25% power and reflux for 1 hour.

Proper reflux is necessary.

At 1/2 hour and 45 minute mark, use 9 inch pipet to wash any cyclohexene in the condenser back in to the reaction flask with hot water. Pipet the solution to a small beaker.

Do not pipet off any phase transfer or catalyst.

Cool the beaker in the ice bath.

Pipet off all the liquid but the 10% of the aqueous reaction mixture.

A precipitate will form. Collect the crude product by vacuum filtration using a Hirsch funnel. After the material dries, weight and take a melting point. If the melting point of the adipic acid is below 151-153 degrees celsius, recrystallize it using hot water. Obtain an IR spectrum of the product.

Results/ Calculations: Density of cyclohexene: 0.811 g/mL. = 2.00g cyclohexene x 0.811 = 2.5 mL of cyclohexene needed. Mass of adipic acid: 0.000987g. Yield percentage: 0.000987g/2.00g x 100 = 0.04935% recovery. Literature melting point: 151-153 degrees celsius. Experimental melting point: 154.5 degrees celsius.

6th July, 2021

Page 3 of 6

IR Spectrum:

Discussion: In this lab experiment, we synthesized adipic acid from cyclohexene. Adipic acid is synthesized through nitric acid oxidation of cyclohexanol. However, this results in emission of nitrous oxide which is harmful for the environment. Oxidative cleavage of cyclohexene can be accomplished by potassium permanganate. However, this results in emission of MnO2 which is very hazardous. Hence, we perform the experiment using 30% of hydrogen peroxide as the oxidant, aliquat-366 as a phase transfer catalsyst and sodium tungstate as a catalyst. This reaction produces water which isn’t hazardous. Our yield percentage was 0.04935% of the adipic acid. Throughout the reflux, we washed the condensate in the lower portion of the condenser back. If this was not properly washed off, this may result in less cyclohexene reacting with adipic acid. We also stopped transferring the solution of adipic acid between he upper cyclohexene layer and the bottom catalyst layer of the flask before it was completely removed to avoid contamination. This may leave some product in the flask. Our melting point was 154.5 degrees celsius which is close to the literature melting point which is 151-153 degrees celsius. Since our experimental melting point was not below the literature melting point, our sample was pure and we did not have to recrystallize it. The sample was fairly pure with very few impurities. Impurities can occur due to glassware contamination,

6th July, 2021

Page 4 of 6

or if the upper layer of the flask content was included during the transfer to the product beaker which included some cyclohexene, or inclusion of the bottom layer which included phase catalyst. The experimental IR spectrum was similar to the literature IR spectrum. The experimental IR spectrum is shown above. In this experiment, we used the concept of green chemistry to generate better, safer and healthier methods of production.

References:

Department of Chemistry. (2015-2017). CHM 205/206 Lab Manual. Miami, Florida: University of Miami at Coral Gables. Padias, Anne B “Making the connections: A how to guide for organic chemistry lab techniques”. New York: Hayden McNeil, 2007.

6th July, 2021

Page 5 of 6

Post lab questions: 1. - Prevention: Prevented the use of N2O and MnO2 as wastes from adipic acid. - Catalysts: Used Aliqaut 366 phase transfer catalyst and sodium tungstate. - Less hazardous chemical syntheses: Less hazardous byproducts were produced; water and less toxic reagents. 2. Reaction of adipic acid with diamine to produce nylon 6-6:

3. a) the current industrial preparation of adipic acid involves the oxidative cleavage of cyclohexenol or cyclohexanone with nitric acid as the oxidant. cyclohexenol or cyclohexanone is produced from benzene and the byproduct of the oxidation is nitrous oxide. b) nitrous oxide is a greenhouse gas that is more potent than carbon dioxide. It contributes to global warming by reflecting radiation back towards the planet and causing ozone depletion exposing the planet to more harmful radiation.

6th July, 2021

6. B

Page 6 of 6...