Oxidation of gallic acid and other polyphenolic benzoic acids

[zalamander]

I am supervising a student who would like to investigate factors affecting the hydrolysis of tannic acid into gallic acid. We came up with the idea of using oxidation with acidified permanganate or dichromate as a means of monitoring the process. However I can't find any information online or in any texts that explain this oxidation process.

 

All I managed to dig up is some info that states oxidation of o,p substituents of dihyroxybenzenes is easy.

 

Can anyone give me some info on what happens during the oxidation of gallic acid under these conditions? My reasoning tells me that only the para group will undergo oxidation with the two meta substituents being unaffected.

 

I'd appreciate if anyone could correct me upon this and to give me an idea as to the reaction mechanism that occurs.

 

I would also appreciate it if any suggestions could be made as to an alternative way of monitoring this process besides colour change during oxidation (using high school lab equipment).

 

Thanks in advance