Which one is most reactive towards electrophilic reagent?
The most reactive towards electrophilic reagent is o-cresol.
The phenolic −OH group increases the electron density of benzene ring through resonance.
With increase in the electron density, the reactivity towards electrophilic reagent increases. The decreasing order of the activating influence of the substituents towards electrophilic reagents is -NR2 > -NHR > -NH2 > -OH>-OR>-NHCOR>