# Why does phenol react on oxygen in the Gattermann–Koch reaction?

When discussing the Gattermann–Koch reaction on phenol substrates, it has been said that O-acylation is a problematic competing reaction as

in a phenol, there's high electron density on the O atom [...]

However, there are also numerous other reactions where phenol reacts with electrophiles on the benzene ring. Some examples are:

Why is the Gatterman–Koch reaction an exception?

• Can anyone please explain what's wrong with my question? Sep 13, 2017 at 21:13
• There isn't really any literature evidence to support the fact that it does react @ oxygen (though it is quite probable). In the Gattermann-Koch mechanism, the intermediate is highly reactive, the Gattermann modification avoids this, making it amenable to synthesis (Gattermann conditions + phenol are fine and have been used in many syntheses). The original Gatterman report of phenols not being amenable to G-K conditions is @ DOI: 10.1002/jlac.19073570209 (German language, very hard to decipher), DOI:10.1002/0471264180.or009.02 also has an overview (English language). Sep 15, 2017 at 19:47
• @NotEvans. I've read the abstract of the English version which says that the Gattermann reaction with $\ce{CN}$ as a reagent reacts on benzene, but I am confused about the Gattermann koch version. Sep 15, 2017 at 20:21