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NAME: CHIDERA MARY OKEKE

TITLE: OXIDATION OF CYCLOHEXANOL TO CYCLOHEXANONE AND OXIDATION OF CYCLOHEXANONE TO ADIPIC ACID

LAB PARTNER: LEIANA WOODARD, MIKAYLA JORDAN, MAURI MOORE

SECTION: TUESDAY 2:50 – 5:50

DATE: FEBUARY 25TH, 2020

PURPOSE The purpose of this lab is to synthesize cyclohexanone from cyclohexanol using hypochlorite as the oxidizing agent, to oxidize cyclohexanone to adipic acid and to determine the percent yield of both cyclohexanone and adipic acid. INTRODUCTION2 In this experiment, alcohols were converted into carbonyl group through oxidation. Oxidation reaction is the loss of an electron or an increase in oxidation state. It always occurs with reduction reaction, which is the gain of an electron. Cyclohexanol is the reductant and the product of bleach reacted with acetic acid, HOCl, is the active oxidant. The product of the reaction is cyclohexanone. Oxidation of a primary alcohol produces aldehydes; secondary alcohols are oxidized into ketones, like cyclohexanol being oxidized into cyclohexanone. Primary alcohols may be oxidized to aldehydes, and then to carboxylic acids. Tertiary alcohol cannot be oxidized under standard condition because there is no C-H bond to break, C-C bond has to be broken to oxidize tertiary alcohol. Chromic acid is a common and effective oxidizing reagent, however in this experiment, bleach is used as the oxidizing agent to replace chromic acid because bleach is safer and easier to handle in lab. Chromic acid and its byproducts are highly toxic, corrosive and environmental hazard. The reaction studied is important because its product, cyclohexanone, is an important precursor of nylon 6 and nylon6, 6. This makes it one of the largest mass-produced chemicals in the industry. Billions of kilograms of cyclohexanone are produced each year for the making of nylon. Nylon 6 is an important material in gears, ropes, filaments, bearing and automotive industry. The synthesis of cyclohexanone to adipic acid is simple. First, sodium hypochlorite and acetic acid are reacted to yield hypochlorous acid. Second, hypochlorous acid is added to cyclohexanol to synthesize cyclohexanone via Chapman-Stevens oxidation reaction. After cyclohexanone is synthesized, it must be separated out from by-products. In order for it to be separated out, sodium chloride is added to the mixture. The sodium chloride will salt out the cyclohexanone from the aqueous layer. Now the aqueous layer and the cyclohexanone must be separated. Dichloromethane is added to the mixture. Next, the cyclohexanone and dichloromethane are separated from the aqueous layer by liquid-liquid separation. The top layer

should be the aqueous layer, while the bottom layer should be organic and contain the final product, cyclohexanone. Last, the dichloromethane is boiled off to leave only the final product.

Potassium permanganate, potassium dichromate, concentrated nitric acid are all common oxidizing agents in organic experiments. Oxidizing reactions are usually exothermic reaction. Cyclohexanol can be oxidized to cyclohexanone. Then then carbon chain can be broken and get adipic acid but under the effect of strong oxidizing agent such as concentrated nitric acid or potassium permanganate.

EXPERIMENTAL MATERIALS The materials used in this experiment include 5mL long necked round-bottomed flasks, acetic acid, sodium hypochlorite(household bleach), pH paper, saturated sodium bisulfite solution,

mercury thermometer, sand bath, starch-iodide paper, thymol blue indicator, Pasteur pipette, distilled water, cyclohexanol, 6M sodium hydroxide solution, boiling chip, thermometer adapter, sodium chloride, ether, 10mL measuring cylinder, potassium permanganate, cyclohexanone, 125mL Erlenmeyer flask, 3M sodium hydroxide solution, ice, filter paper, Buchner funnel, decolorizing charcoal, and hydrochloric acid were used in the experiment. PROCEDURE1 CYCLOHEXANONE FRO CYCLOHEXANOL THROUGH HYPOCHLORITE OXIDATION To a 5-mL long necked, round-bottomed flask fitted with a connector, 150 mg cyclohexanol and a mixture of 50mg acetic acid and 2.3mL of 5.25% solution hypochlorite were added. The mixture was checked for acidity and when it was still basic, acetic acid was added and temperature was checked. The temperature rose to 43℃ . As soon as the temperature began to drop, the thermometer was removed, the flask was capped and shaken, and then the flask was keep at 45℃ for 15 minutes. Excess oxidizing agent was destroyed by adding saturated sodium bisulfite solution. At that point, reaction no longer gave a positive test with starch-iodide paper. A drop of thymol blue was added and neutralized with 0.4mL 6M sodium hydroxide solution. A boiling chip was added, a distilling head, thermometer adapter, and a thermometer were attached. About 0.8mL of a mixture of water and cyclohexanone was distilled.

ISOLATION To a 5-mL long necked, round-bottomed flask fitted with a connector, 150 mg cyclohexanol and a mixture of 50mg acetic acid and 2.3mL of 5.25% solution hypochlorite were added. The mixture was checked for acidity and when it was still basic, acetic acid was added and temperature was checked. The temperature rose to 43℃ . As soon as the temperature began to drop, the thermometer was removed, the flask was capped and shaken, and then the flask was keep at 45℃ for 15 minutes. Excess oxidizing agent was destroyed by adding saturated sodium bisulfite solution. At that point, reaction no longer gave a positive test with starch-iodide paper. A drop of thymol blue was added and neutralized with 0.4mL 6M sodium hydroxide solution. A boiling chip was added, a distilling head, thermometer adapter, and a thermometer were attached. About 0.8mL of a mixture of water and cyclohexanone was distilled.

ADIPIC ACID FROM CYCLOHEXANONE 0.5g of cyclohexanone and 1.5g of potassium permanganate were mixed with 12.5mL of water in a 125mL Erlenmeyer flask and the temperature was adjusted to 30℃. 0.1mL of 3M sodium hydroxide solution was then added. When the temperature reached 45℃, the oxidation was slowed by brief ice-cooling and keep at 45℃ for 20 minutes. The mixture was then heated by swirling on hot plate to complete oxidation and coagulate precipitated manganese dioxide. A spot test was done to see if permanganate was still present. When permanganate was still present, small amounts of sodium bisulfite solution was added until the spot test was negative. The mixture was filtered by suction on an 11-cm Buchner funnel, brown precipitate was washed with water, boiling chip was added, and evaporated on a hot plate to a volume of 35mL. When solution was not clear, it was clarified with decolorizing charcoal and evaporated to 35mL. It was then acidified with ions from hydrochloric acid to a pH of about 1-2, 5mL acid was added in excess and left to crystallize. The crystals were collected on a Buchner funnel and washed with cold water. The mass and percentage yield of adipic acid were obtained.

DATA AND RESULTS

Mass of cyclohexanol Mass of cyclohexanone Mass of adipic acid

0.15g 1.013g 0.312g

Percent yield of cyclohexanone = 675.3% Percent yield of adipic acid = 62.4% SAMPLE CALCULATION Percent yield of cyclohexanone = =

actual yield ×100 theoritical yield 1.013 ×100 0.15

= 675.3% Percent yield of adipic acid = =

actual yield ×100 theoritical yield 0.3 12 × 100 0.5

= 62.4% DISCUSSION An average yield of cyclohexanone is 675.3% (1.013g) of product. It’s possible that mistakes were made during the preparation of the product. The first observation that was seen during the reaction was the temperature change. The temperature was below 30 °C while adding the mixture of sodium hypochlorite and acetic acid, which is also known as hypochlorous acid. Then while the hypochlorous acid and cyclohexanol was being stirred, the temperature began to rise. The temperature only rose to about 40°C. If the mixture was yellow in color, it contained too much hypochlorous acid. Sodium bisulfide was added to destroy excess oxidizing agent. The solution was distilled and then cyclohexanone was isolated. The final product was yellowish in color and a liquid. One possible reason for a low yield is that the temperature did not reach above 45°C. This could have caused the reaction to not go to completion giving a much lower yield. The product that was lost could not be later recovered. 0.5g of cyclohexanone was used to prepare the adipic acid with potassium permanganate. The oxidation of cyclohexanone to adipic acid produced a dark brown residue which is manganese dioxide. A spot test was used to determine if the oxidation had occurred. The oxidized mixture was filtered by suction and the residue was removed. The filtrate was evaporated and crystallized to form adipic acid. The crystal was tested with litmus and the litmus turned red proving the presence of an acid.

O

O

KMnO4, NaOH, H2O OH HO O

- MnO3

OH O

O

O

O O

O OH

Mn

Mn

O

O O O

OH

O

O

O O

OH

O

O

Mn

OH

Mn

O O O

O

H2O OH

OH

O O

O

O

- MnO2

Mn O

O

O

O O

Mn O O

The possible sources of error in this lab include incomplete transfer/ spillage of the compounds during transfer, incomplete isolation of crystals during suction filtration, dissolution of some crystals to water (since adipic acid is partially soluble in water) and a possible presence of side products.

CONCLUSION The experiment was successful. The synthesis of cyclohexanone is a simple procedure that uses acetic acid, sodium hypochlorite, hypochlorous acid, ether, sodium chloride, sodium carbonate and cyclohexanol. The reaction is a Chapman-Stevens oxidation. The synthesis is done by simply adding the acetic acid and sodium hypochlorite, which is also known as hypochlorous acid to cyclohexanol and then separating the final product from the by-products. The final results of the synthesis of cyclohexanone are that we had a 675.3% yield and that it is not 100% pure. The adipic acid crystals were white and weighed 0.312g. The percent yield of adipic acid is 62.4%. Although the percent yield if the adipic acid looks good, the percent yield of the cyclohexanone produced is very wrong as it is over 100%. The cyclohexanone contained impurities and the adipic acid most like contains impurities too.

REFERENCES

1. Williamson, Kenneth L. Techniques Labs for Macroscale and Microscale Organic Experiments. Brooks/Cole, 2012. 2. Pavia, D. L., Lampman, G. M., Kriz, G. S., Engel, R. G. Introduction to Organic Laboratory Techniques: A Microscale Approach. 2007.

POST LAB 1. In the hypochlorite oxidation of cyclohexanol to cyclohexanone, what purpose does the acetic acid serve? Answer: It acts as a catalyst. It turns sodium hypochlorite into hypochlorous acid whose ion acts as a nucleophile in the oxidation reaction. 2. Explain the order of the chemical shifts of the carbon atoms in the carbon-13 spectra of cyclohexanone and adipic acid. Answer: The carbon atoms that are closest to the carbonyl ring will have a chemical shift that is more downfield due to the effect of the electronegative oxygen atom. On the carbonyl group....