Low-temperature heat capacity and thermodynamic parameters of γ-aminobutyric acid

Autor: Yu. A. Kovalevskaya, I. E. Paukov, Elena V. Boldyreva
Rok vydání: 2012
Předmět:
Zdroj: Journal of Thermal Analysis and Calorimetry. 111:2059-2062
ISSN: 1572-8943
1388-6150
DOI: 10.1007/s10973-012-2405-4
Popis: Thermodynamic properties of γ-aminobutyric acid were studied in the temperature interval from 5.7 to 300 K using a vacuum adiabatic calorimeter. The curve C p (T) in the mentioned temperature interval is S-shaped without any anomalies. Based on the smoothed values of heat capacity, the calorimetric entropy $$ S_{m}^{0} (T) - S_{m}^{0} (0) $$ and the difference in the enthalpies $$ H_{m}^{0} (T) - H_{m}^{0} (0) $$ were calculated and tabulated. At the standard temperature 298.15 K, these values are equal to 158.1 ± 0.3 J K−1 mol−1 and 23020 ± 50 J mol−1, respectively. At temperatures from 5 to 10 K, the function C p (T) was found to obey the Debye law C = AT 3. Contrary to what has been supposed previously, the empirical Parks–Huffman rule for estimating entropy in the homologous series was shown to be not valid for the series glycine–β-alanine–γ-aminobutyric acid.
Databáze: OpenAIRE
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