Sciencemadness Discussion Board

Benzene ---> Phenol

Derek McOlund - 4-12-2016 at 05:17

Have anyone an idea of how to turn benzene to phenol? I know of the cumene process, but is there any easier method? I've heard that you'd extract phenol from coal tar back in the days, does anyone know how that can be done?
I know that phenol can be reduced to benzene using zinc
C6H5OH + Zn → C6H6 + ZnO, but can you oxidize benzene to obtain phenol?

unionised - 4-12-2016 at 06:06

Chlorination then hydrolysis of chlorobenzene is an alternative, but it's not any easier than the cumene process.

CuReUS - 4-12-2016 at 08:04

previously,the direct hydroxylation of arenes was done by fenton's reagent.But the reaction is messy and the yield is poor,so over the years there have been many modifications.

DDTea - 4-12-2016 at 13:27

Natural and synthetic P450's, such as the Groves metal porphyrin catalysts and improvements thereupon (Dolphin-Chorghade system has best performance as far as I know), will oxidize benzene to phenol. The trouble is they don't *stop* at phenol, and will oxidize benzene all the way to benzoquinone.

The catalytic oxidation of benzene to phenol using atmospheric oxygen or H2O2 would be of enormous commercial significance. It would be an improvement in atom economy over the existing cumene process.


Additionally, N2O has been used to oxidize benzene to phenol over zeolite catalysts. Selectivity for phenol is high but conversions are low (20 - 25%). Google turned up a ton of papers with the search terms "benzene" "N2O" "phenol."

The story isn't much different with homogeneous catalysts, it seems. Here's a homogeneous nickel catalyst that hydroxylates benzene with H2O2 to selectively form phenol, with <1% benzoquinone.

Outside the realm of catalysis, phenyl lithium and phenyl magnesium bromide may be converted to phenol in good yields. These are stoichiometric reactions, of course, and would require pre-synthesis of the organometallic reagent from bromobenzene. Thus it becomes a two-step process, and the oxidants aren't readily available to the amateur (tert-butylhydroperoxide).

This is an interesting research question. If you can find a good way to form a phenyl radical from benzene (a high energy endeavor, for sure) and to quench it with H2O2, you might have the beginnings of a pathway to phenol.

[Edited on 12-4-16 by DDTea]

UC235 - 4-12-2016 at 21:14

If this is a theoretical question, see above. If you've a practical interest in preparing phenol, see my writeup in Prepublication subforum starting from aspirin/salicylic acid.

S.C. Wack - 4-12-2016 at 21:51

Nitration or sulfonation first.