Reaction mechanism for the synthesis of 9,10-phenanthrenequinone In my lab course I had to synthesize 9,10-phenanthrenequinone (phenanthrene-9,10-dione) from phenanthrene and chromium(VI) oxide. The synthesis was made as explained in Organic Syntheses, Coll. Vol. 4, p.757 (1963)

The reactants are: phenanthrene (1.00 eq), chromium(VI) oxide (7.50 eq), sulfuric acid (15.0 eq), water (83.3 eq)

I now have to explain the reaction mechanism, but unfortunately I don't find it in any of my textbooks, neither on the internet.

Here is my assumption:


The chromium(VI) oxide reacts with water and forms chromic acid.
The chromic acid can oxidize an alcohol to a ketone (Jones-Oxidation)


So what misses is the alcohol. Somehow I have to get the 9,10-phenanthrenediol, which could react as alcohol in the Jones-Oxidation.

How could this possibly work. Remember, I don't have $\ce{OsO4}$, which could easily dihydroxilate an alkene.



EDIT 1: As an answer to the proposed mechanism by @Zhe:

Is this ok in your eyes?





EDIT 2: An other idea for the first step (dihydroxilation)

A person of the scientific staff of my university told me, that the $\ce{CrO3}$ should react in a very similar way as $\ce{OsO4}$ does. As I'm using 7.50 eq of chromium(VI) oxide, there is enough for the dihydroxilation and the Jones-Oxidation. He said that a radical mechanism is rather unlikely, because I'm working with water as solvent and water is an inhibitor for radical reactions. This is the mechanism I came up with, regarding these new information.



What do you think about this possibility?
Here's what I was thinking.


  This probably happens via a single electron oxidation of that double bond to a radical cation as a first step. The cation can trap water and then we can oxidize the radical to a cation. Eventually, you get to a diol which you can oxidize to a diketone.




I ommited the steps for chromium oxidation from the alcohol to the ketone. Sounds like you are already familiar with those.