The `OH` group of phenol

Options

A. activates ring powerfully and direacts ortho, para in nucleophilic aromatic substitution.
B. activates ring powerully and direacts ortho, para in electrophilic substitution
C. deactivates powerfully and directs ortho, para in electrophile aromatic substitution
D. deactivates powerfully and directs meta in electrophilic aromatic substitution.

Answer

B

Explanation

Like the amino group, the phenolic group powerfully activates aromatic rings toward electrophilic substitution in essentially the same way.

The intermediates are hardly carbocations at all, but rather oxonium ions `(A and B)` in which every atom (except hydrogen ) has a complete octet of electrons. they are formed tremendously faster than the carbocations derived from benzene itsself.
Attack on a phenoxide ion yields an even more stable (and hence even more rapidly formed) intermediate, an unstaturated ketone `(C and D)`

With phenols (as with amines) special precautions must often be taken to prevent polysubstitution and oxidation.