[roze]

I am looking for some information of the preparation of cyclohexanol from cyclohexene, sulphuric acid and water.  ie the mechanism reaction and theory.  The experiment uses dislillation and sepration techniques. I seem to find a lot on the revserse ie preparation of cyclohexene from cyclohexanol but the experiments are slighly different.

any web references woudl be helpful

[dexangeles]

look for acid catalyzed hydration of alkenes

[hmx9123]

That reaction is done in just about every basic organic lab across the country.  Check out both textbooks, and lab manuals that you find.

[AWK]

Cyclohexanol is easily dehydrated with sulfuric acid  to cyclohexene. The reverse reaction needs other catalysts, eg zeolites

[achiral]

What is the white fume in the final stage of the preparation of cyclohexene from cyclohexanol with phosphoric acid?
Thank you.

[Mounia88]

it is better to use phosphoric acid int his experiment because sulfuric acid has many secondary reactions
and the mechanism is attached to the post


-Pour cyclohexanol (20 mL, b.p. 161°) into a 50 mL round bottom flask (small neck) and cautiously add 85% phosphoric acid (5 mL). Add boiling chips and arrange for a distillation using a cooled 10 mL graduated cylinder as a receiver. (Cool the cylinder by standing it in a beaker of ice and water).
We preformed a distillation to separate the cyclohexene from the cyclohexanol and to stop the reverse reaction from happening and that is turning the cyclohexene back to cyclohexanol.
We stop heating at around 110oC and we do it to avoid recuperating cyclohexanol. We stop heating when we stop seeing product in the refrigerator.
 

-But the crude product is contaminated with water, unreacted alcohol, phosphoric acid and some side products. Washing with water removes most of the impurities. Treatment with solid sodium chloride (until saturation) removes traces of acid and a final wash with water removes any remaining carbonate.


-Then we add a solution of sodium carbonate (10%) to neutralize the acid left
And we pour the mixture into a separation flask and we separate the organic phase that is floating and that contains cyclohexene from the aqueous phase that contains all other residues.
Finally we add a dehydrator to the organic phase to eliminate any water that might have stayed from the separation.

 




-   Testing the unsaturation:
We chose to test the unsaturation with potassium permanganate that can identify an unsaturation in the product knowing that we can also identify unsaturation by adding a brome based solution.
In the presence of an unsaturation the permanganate has a brown color and the brome solution color disappears.
In a testing tube we pour a few mL of the product with a few drops of purple potassium permanganate the mixture takes a brown coloring.
We didn’t test it with the brome solution.
The permanganate turns the cyclohexene into a diol. A hydroxylation takes place the reaction product is the glycol.
During the reaction the purple permanganate is reduced into manganese dioxide.


This reaction is used to test the presence of an alkene (the Bayer test).

 


The permanganate is introduced as a liquid, but in fact this solution is prepared from crystals of KMnO4. This ion solution is added as a liquid so it can react with the alkene. If it was added as a solid it wouldn’t be able to dissolve in the organic phase.
We have to say that permanganate in the presence of an unsaturation turns from purple to brown, and dibromide turns from reddish to colorless.