In addition , the rates at four temperatures were measured for seven of the dienes permitting calculations of the enthalpy of activation ( ΔH ‡ ) and entropy of activation ( ΔS ‡ ) for these reactions through the Arrhenius equation .
From these measurements , chemists used the Arrhenius equation to calculate the enthalpy of activation ( ΔH ‡ ) and entropy of activation ( ΔS ‡ ) for each reaction .