The standard (p degrees = 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 (p degrees = 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. (c) 2012 Elsevier Ltd. All rights reserved.