Free energy relationships via tautomerism in para-acetophenone derivatives

► The energy parameters of tautomerism in acetophenones were calculated by DFT method. ► The results show linear relations between log(Keq/KeqH) and σp, σR or R. ► The best correlation was observed when σp values were used as substituent constants. ► By the increase of electronegativity of substituent, Keq increases and k decreases.