The presence of –OH group in phenols activates the aromatic ring towards
electrophilic substitution and directs the incoming group to ortho and para
positions due to resonance effect Reimer-Tiemann reaction of phenol yields
salicylaldehyde In presence of sodium hydroxide, phenol generates phenoxide
ion which is even more reactive than phenol Thus, in alkaline medium, phenol
undergoes Kolbe’s reaction