demorol (Hive Bee)
03-21-02 12:04
No 285980
      Oxidation of cyclohexanol with KMnO4?  Bookmark   

My question is very simple. Is there any chance to use KMnO4 instead of sodium dichromate in oxidation of cyclohexanol. I have already UTFSE but no useful answers were found. References are also wanted (if there are any).

Life without chemistry would be a mistake.
(Hive Bee)
03-21-02 12:32
No 285993
      Oxidation of cyclohexanol with KMnO4
(Rated as: excellent)

Are you talking about this :

Procedure: Cautiously add 20 ml of conc. sulfuric acid to 60 g of crushed ice and mix well. Add 20 g of cyclohexanol and place a thermometer in the mixture (temp. should be <30 C). Prepare a solution of 21 g sodium dichromate dihydrate in 10 ml of water. Add about 1 ml of this solution to the reaction flask with vigorous swirling. Add the rest of the dichromate solution with continuous swirling at a rate that keeps the temperature between 25 and 35 C. After the addition is complete, continue stirring until the temperature falls by 1 or 2 degrees. Add about 1 g of solid oxalic acid to destroy any excess dichromate. Rinse the reaction mixture into a 500 ml distillation flask with 100 ml of water, add a boiling stone, and distill the product rapidly. The cyclohexanone will distill as a mixture with water (an azeotrope) at about 95 C. Continue distillation until 60-100 ml of distillate is obtained. Add about 15 g of sodium chloride to the distillate and swirl until most of it has disolved. Transfer the mixture to a seperatory funnel and discard the lower aqueous layer. Dry the upper layer with 1-2 g of potassium carbonate and decant. The cyclohexanone will now be of sufficient purity to use in PCP synthesis, but if further purification is desired, it can be redistilled.

(Hive Bee)
03-21-02 12:45
No 286004
      maybe  Bookmark   

I read somewhere that KMnO4 is soluble in acetone.

So you maybe able to perform the oxidation with just cyclohexanol, acetone and KMnO4 (under reflux). Use iso-propanol alcohol to destroy the left KMnO4. then the mixture can be distilled (Cyclohexanone BP = 156.7c)

Umm, how interesting !!
(Hive Bee)
03-21-02 13:11
No 286019
      Another way !
(Rated as: excellent)

Chapter 22 Procedure #4 Oxidation of Cyclohexanol

1. Use 250 ml Beaker equipped with a magnetic stirrer and the 8 ml cyclohexanol

2. Set beaker on a stirring platform

3. Mix 4 ml of Glatial Acetic Acid with 115 ml of household bleach (NaClO)

4. Place the mixture in a 125 ml Separatory Funnel

5. Attach sep funnel on a ring stand directly above the beaker

6. Turn the stirring platform on so the magnetic stirrer rotates without splashing

7. Suspend a thermometer attached to the ring stand directly into the mixture in the beaker.

8. Add the acidified bleach from the sep funnel into the beaker at a rate of 2 drops per second which should take 20 minutes while stirring with the stirrer. Do not let the temperature to go above 50 degrees. Have an ice bath on standby in case it drifts above 50.

9. Allow the reaction mixture to stir for an additional 20 minutes.

10. Heat the reaction mixture to 50 degrees C using a hot plate

11. Add 1 gram portions of NaHSO3 in order to reduce any excess bleach. Test using Starch-Iodide paper until the paper ceases to turn dark blue. Add 1 gram then stir and test with paper. If a positive test is secured then repeat the procedure with an additional 1 gram portion until a negative test is secured.

12. Add 3 drops of Thymol Blue indicator solution.

13. Add 15-20 ml of 6M NaOH and check for a sky blue color of solution. If the solution is not blue (for example green) then add an additional 5 ml of the 6M NaOH.

14. Transfer the reaction mixture to a 250 ml Round Bottom Distilling Flask. Rinse the beaker with 5 ml of water and transfer rinse to flask.

15. Simple distill (steam distill) collecting 40 ml of co-distillate (water and cyclohexanone) into a graduated cylinder as a receptacle.

16. Add 8 grams of solid Sodium Chloride to the co-distillate and stir to dissolve.

17. Transfer the co-distillate to a 125 ml separatory funnel

18. Rinse the graduated cylinder that you collected the co-distillate in using 5 ml of Methyl t-Butyl Ether and transfer into the separatory funnel.

19. Add 10-15 ml more of the ether to the separatory funnel, shake, and allow to separate.

20. Draw off the bottom water layer and discard into the sink.

21. Add 10 ml of 3M NaOH to the separatory funnel, shake, and allow layers to separate.

22. Draw off the lower water layer and discard

23. Add 15 ml of saturated Sodium Chloride solution, shake, and let the layers separate.

24. Draw off lower water layer and discard

25. Transfer ether layer to a 50 ml Erlenmyer Flask through the top of the funnel.

26.Add Na2SO4 (anhydrous) to the flask so as to just cover the bottom.

27. Dry for 10 minutes.

28. Decant dryed ether extract into a pre-weighed 50 ml Erlenmyer Flask that has a wood stick.

29. Place the 50 ml flask in a preheated water bath located under a vent hood.

30. Allow the ether to boil off. When bubbling stops after boiling has begun then the boiling process is complete.

31. Dry flask off and weigh

32. Calculate the % yield

33. Take an IR and a GC.

34. Keep the product cyclohexanone for the next experiment (#6)

Umm, how interesting !!