For most reactions the activation enthalpy and activation entropy are unknown, but, if these parameters have been measured and a linear relationship is found to exist (meaning an LFER was found to hold), the following equation describes the relationship between Δ H i and Δ S i : Δ Δ H ‡ ‡ = β β Δ Δ S ‡ ‡ + Δ Δ H 0 ‡ ‡