Abstract: Molar heat capacities of (S)-ibuprofen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 370 K. Experimental heat capacities were fitted into a polynomial equation of heat capacities (Cp,m) with reduced temperature (X), [X=f(T)]. The polynomial equations for (S)-ibuprofen wereCp,m(S)= －39.483X4－66.649X3＋95.196X2＋210.84X＋172.98 in solid state and Cp,m(L)= 7.191X3＋4.2774X2＋56.365X＋498.5 in liquid state. The thermodynamic functions relative to the reference temperature of 298.15 K, HT－H298.15 and ST－S298.15, were derived for the(S)-ibuprofen. A fusion transition at Tm=(324.15±0.02) K was found from the Cp－T curve. The molar enthalpy and entropy of the fusion transition were determined to be (18.05±0.31) kJ•mol－1 and (55.71±0.95) J•mol－1•K－1, respectively. The purity of the (S)-ibuprofen was determined to be 99.44％ on the basis of the heat capacity measurement. Finally, the heat capacities of (S)-ibuprofen and racemic ibuprofen were compared.

Key words: (S)-ibuprofen, Adiabatic calorimetry, Heat capacity