Acta Phys. -Chim. Sin. ›› 2005, Vol. 21 ›› Issue (01): 1-5.doi: 10.3866/PKU.WHXB20050101

• ARTICLE •     Next Articles

Low Temperature Heat Capacity of (S)-ibuprofen

XU Fen;SUN Li-Xian;TAN Zhi-Cheng;LI Rui-Lian;TIAN Qi-Feng;ZHANG Tao   

  1. Materials & Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023; Hunan Institute of Drug Detection, Changsha 410001
  • Received:2004-06-11 Revised:2004-07-15 Published:2005-01-15
  • Contact: SUN Li-Xian

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