oxidation of cyclohexanol to adipic acid
TRANSCRIPT
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!