Low-temperature thermal properties of 2,2-dimethyl-1,3-propanediol and its deuterated analogues |
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| Institution: | 1. Kirensky Institute of Physics, Federal Research Center KSC SB RAS, 660036 Krasnoyarsk, Russia;2. Institute of Engineering Physics and Radioelectronics, Siberian Federal University, 660074 Krasnoyarsk, Russia;3. Institute of Engineering Systems and Energy, Krasnoyarsk State Agrarian University, 660049 Krasnoyarsk, Russia |
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| Abstract: | Heat capacities of 2,2-dimethyl-1,3-propanediol(CH3)2C(CH2OH)2 were measured in the temperature range between T = 13 K and T = 350 K using an adiabatic calorimeter. The compound underwent a first-order phase transition at T = (314.5 ± 0.1) K. The enthalpy and the entropy of transition were (12.52 ± 0.02)kJ · mol − 1and (39.81 ± 0.08)J · K − 1· mol − 1, respectively. Measurement of the fusion peak by d.s.c. showed that the purity of the sample was 0.9999 mass fraction and the entropy of fusion was 9.9 J · K − 1· mol − 1. Another first-order phase transition was observed at T = (60.4 ± 0.1) K with the associated entropy change of (2.93 ± 0.05)J · K − 1· mol − 1. Heat capacities of two deuterated samples,(CH3)2C(CH2OD)2 and(CD3)2C(CD2OD)2 , were also measured and the results were compared with those on the natural compound. Possible mechanisms of the transition have been discussed from the isotope effects on the thermodynamic quantities associated with the transition. Standard thermodynamic functions of the compounds are tabulated. |
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