کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
215799 | 1426255 | 2013 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Experimental and computational study on the energetics of the cyclic anhydrides of glycine and alanine Experimental and computational study on the energetics of the cyclic anhydrides of glycine and alanine](/preview/png/215799.png)
The standard (p° = 0.1 MPa) molar enthalpies of formation, in the crystalline phase, of the cyclic anhydrides of glycine and DL-alanine, at T = 298.15 K, were derived from the standard molar energies of combustion in oxygen, measured by static bomb combustion calorimetry. For these compounds, the standard molar enthalpies of sublimation, at T = 298.15 K, were determined from the temperature-vapour pressure dependence, obtained by the Knudsen mass-loss effusion method. Through the values for the heat capacity differences between the gas and the crystalline phases of the studied compounds, the standard (po = 0.1 MPa) molar enthalpies, entropies and Gibbs energies of sublimation, at T = 298.15 K, were derived. From the experimental values, the standard molar enthalpies of formation, in the gaseous phase, at T = 298.15 K, of glycine anhydride and DL-alanine anhydride were calculated as –(321.0 ± 1.9) kJ·mol−1 and –(382.7 ± 2.0) kJ·mol−1, respectively. A theoretical study at the G3 and G4 levels has been carried out, and the calculated enthalpies of formation have been compared with the experimental values.
► Study on the energetics of the cyclic anhydrides of glycine and alanine.
► Experimental and computational thermochemistry of glycine and alanine anhydrides.
► Ab initio calculations for two cyclopeptides obtained by G3(MP2)//B3LYP method.
Journal: The Journal of Chemical Thermodynamics - Volume 58, March 2013, Pages 29–35