Oxidation of Cyclohexanol to Adipic Acid

OXIDATION OF CYCLOHEXANOL TO ADIPIC ACID

A special synthesis in Chemistry 44.1

by

David Joram Mendoza

Recall Exer 2: Oxidation of a secondary alcohol ( cyclohexanone from cyclohexanol)

• cyclohexanol is oxidized to cyclohexanone with household bleach ( sodium hypochlorite)

In this case, cyclohexanol was oxidized to a dicarboxylic acid 1-6-hexanedioic acid or adipic acid.

* by Mayo, et al. , 2011

Proposed Mechanism*

1. Formation of dicyclohexyl ether

Possible side reactions

This is minimized by the dropwise addition of cyclohexanol with gentle swirling after every drop. This is also minimized by controlling the reaction temperature.

Possible side reactions2. Formation of cyclohexene

This is minimized by the dropwise addition of cyclohexanol with gentle swirling after every drop. This is also minimized by controllingthe reaction temperature.

1. 2 mL of nitric acid was placed in a micro-reflux set-up.

Experimental Procedure

2. The acid solution was heated to 55 – 60 ºC.

3. 1.0 mL of cyclohexanol was added to the acid solution dropwise at a rate of 1 drop per 30 s.

Experimental Procedure

Brown nitrogen oxides

explosive and exothermic!

4. Once the addition of cyclohexanol was completed, the temperature (55 – 60 ºC) was maintained for 30 minutes.

5. The temperature was then elevated to 100 ºC over ( for about 10 minutes) and was further maintained for another 5 minutes.

Experimental Procedure

6. It was cooled to room temperature and was then placed in an iced bath for crystallization of adipic acid.

Experimental Procedure

7. The light yellow crystals were then collected through suction filtration with frequent washings with ice-cold water.

Experimental Procedure

8. The white crystals were then dried and weighed. A percent yield of 87.1 % was incurred.

Experimental Procedure

Percent YieldA percent yield of 87.1 % was incurred.

The possible sources of error include:1. Incomplete transfer/ spillage of

cyclohexanol during the addition to the acid solution

2. Incomplete isolation of crystals during suction filtration

3. Dissolution of some crystals to water ( since adipic acid is partially soluble to water)

4. Possible presence of side products

JONES TEST Red-orange

liquid mixture to green (+)

Chemical tests

For cyclohexanol:

2 + 2CrO3 + H2SO4 3 + 6H2 O + Cr2(SO4 )3

(green)

HOT, ACIDIC KMnO4 TEST

Disappearance of purple color and

formation of brown precipitate (+)

Chemical tests

For cyclohexanol:

+ hot, acidic KMnO4 + MnO2 (brown ppt.)

Chemical tests

For cyclohexanol:Reaction with 10 %

NaHCO3

No evolution of gas (-)

Litmus test

Blue to blue Red to red( neutral)

Chemical tests

For adipic acid:JONES TEST

Red-orange liquid mixture remained (-)

HOT, ACIDIC KMnO4 TEST

Purple liquid mixture (-)

Chemical tests

For adipic acid:Reaction with 10 %

NaHCO3

evolution of CO2

gas (+)

+ 2NaHCO3 + 2CO2 + 2H2O

COO-Na+

COO-Na+

Litmus test

Blue to redRed to red

( acidic)

Chemical tests

For adipic acid:

THEORETICAL MELTING POINT

EXPERIMENTAL MELTING POINT RANGE

152 º C 151- 152 º C

Melting point determination

1. It is the monomer used in the manufacture of nylon -6,6:

Uses of adipic acid

Carpet fiber Apparel Airbags Tires Zip Ties Ropes Conveyor Belts Hoses

USES OF NYLON 6-6

Uses of adipic acid

2. Used in lubricants, synthetic fibers, plastics , polyurethane resins and plastilizers.

3. Small amounts are used as flavoring and gelling aid

4. Used in medicine

Uses of adipic acid

The synthesis is similar to the industrial production of adipic acid wherein a mixture of cyclohexanol and cyclohexanone  (called "KA oil“) is oxidized with nitric acid to give adipic acid, via a multistep pathway.

Disadvantage of the synthesis

This industrial synthesis of adipic acid is

detrimental to the environment. A by-product of the synthesis is nitrous oxide

(N2O) causes global warming and ozone depletion as well as acid rain and smog.

about 400,000 metric tons of nitrous oxide is emitted annually , which corresponds up to 8% of the worldwide anthropogenic emission of N2O

Disadvantage of the synthesis

catalytic oxidation of cyclohexene in

the presence of a phase-transfer catalyst (Aliquat 336).

Green synthesis of adipic acid

The EndThank you for listening!