Low-temperature heat capacities and thermodynamic properties of 2,2-dimethyl-1,3-propanediol |
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Authors: | B Tong Z -C Tan X C Lv L X Sun F Xu Q Shi Y S Li |
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Institution: | (1) Thermochemistry Laboratory, Dalian Institute of Chemical Physics, Chinese Academy of Science, Dalian, 116023, China;(2) College of Environmental Science and Engineering, Dalian Jiaotong University, Dalian, 116028, China |
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Abstract: | The molar heat capacities C
p,m of 2,2-dimethyl-1,3-propanediol were measured in the temperature range from 78 to 410 K by means of a small sample automated
adiabatic calorimeter. A solid-solid and a solid-liquid phase transitions were found at T-314.304 and 402.402 K, respectively, from the experimental C
p-T curve. The molar enthalpies and entropies of these transitions were determined to be 14.78 kJ mol−1, 47.01 J K−1 mol− for the solid-solid transition and 7.518 kJ mol−1, 18.68 J K−1 mol−1 for the solid-liquid transition, respectively. The dependence of heat capacity on the temperature was fitted to the following
polynomial equations with least square method. In the temperature range of 80 to 310 K, C
p,m/(J K−1 mol−1)=117.72+58.8022x+3.0964x
2+6.87363x
3−13.922x
4+9.8889x
5+16.195x
6; x=(T/K)−195]/115. In the temperature range of 325 to 395 K, C
p,m/(J K−1 mol−1)=290.74+22.767x−0.6247x
2−0.8716x
3−4.0159x
4−0.2878x
5+1.7244x
6; x=(T/K)−360]/35. The thermodynamic functions H
T−H
298.15 and S
T−S
298.15, were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The thermostability
of the compound was further tested by DSC and TG measurements. The results were in agreement with those obtained by adiabatic
calorimetry. |
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Keywords: | adiabatic calorimetry 2 2-dimethyl-1 3-propanediol DSC heat capacity phase transition TG thermodynamic properties |
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