[flortzweich]

Hello All,

I am working on a synthesis project in Organic Chemistry involving an oxidation of a benzyllic sidechain hopefully to Benzoic Acid. My question is... I have been looking over the literature and most of what I see is the process of oxidizing toluene or some variation thereof (chloro- nitro- etc...) into benzoic acid. Our process, however, is to oxidize cyclohexylbenzene to benzoic acid using potassium permanganate and a slightly acidic solution. We have already tried the step and have been unsuccessful in getting any benzoic acid to precipitate out. I was wondering if anyone could point me to some references about the oxidation of cyclohexylbenzene specifically.

Our process was to dissolve about 7 grams of potassium permanganate in 40 mL of hot water, add to this the cyclohexylbenzene, and a small amount of HCl. Reflux this for 4 hours and then filter the solution. Reduce any remaining KMnO4 with sodium bisulfite and filter again. Then precipitate out the benzoic acid with concentrated HCl.

There was a large amount of Manganese Dioxide produced, so something was oxidized. The Benzoic Acid, however... strangely elusive. 

Thanks for any help.

[Mitch]

Is this what you mean by cyclohexylbenzene?

[flortzweich]

Yes, we made it by adding cyclohexene to benzene with sulfuric acid in an ice bath, as in the process described at http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0151

This reaction yields a mixture of cyclohexylbenzene and 1,4-dicyclohexylbenzene which is easily separated since the disubstituted is a solid. After we performed this step we used that synthesized cyclohexylbenzene. The IR spec showed we did have cyclohexylbenzene when we added it to the KMnO4 solution.