[mir]

A common problem during phenol synthesis is the formation of phenolic tar. You get a black precipitate, probably because of polymerization. But I havent figured out how it forms, which factors thats important etc, I dont think anyone knows. A short search for it on scifinder, gave only two papers. And they were of course in chinese. Other papers mention it like it was something everybody knows - or nothing to do about it.

How do we prevant phenolig tar formation? And what is the mechanism?

My tutor have a theory, he think acids (one factor we know forms tars) protonate the hydroxy group, and makes it reactive. But he cant explain how.

Is this a radical reaction?

[Custos]

What else is in the synthesis? If you have aldehydes present you might be getting  a thermosetting phenol formaldehyde resin material (like Bakelite). If it's just phenol then at a guess I would say it's some oxidation process causing the polymerisation. I'd try the reaction excluding oxygen and/or using an free radical scavenger.

[mir]

Hydrogen peroxide is present in the solution (so excluding oxygen is no option). Its the oxidant. Do you have an example of a scavenger?

[Custos]

I think you're stuck. A scavenger will not help because you have an oxidant and free radical source (peroxide) present in the reaction.

[mir]

Oh well. But I did an optimization recently. Im studying the response surface now, and I see a hope to reduce the loss of my product