In the Reimer-Tiemann reaction where Phenol reacts with ${\text{CHCl}}_3$ and $\text{NaOH}$, the electrophile involved is:

In the Reimer-Tiemann reaction:${\text{CHCl}}_3$ reacts with ${\text{OH}}^{-}$ to form the trichloromethyl carbanion ${(}^{-}{\text{CCl}}_3)$.This carbanion loses a chloride ion to form the neutral, electron-deficient Dichlorocarbene $(:{\text{CCl}}_2)$.Dichlorocarbene acts as the electrophile that attacks the phenoxide ring.