Standard molar enthalpies of formation of crystalline L-, D- and DL-valine

The standard (p(O) = 0.1 MPa) molar enthalpies of combustion in oxygen, at T = 298.15 K, for crystalline D-, L- and DL-valine were measured by static- bomb calorimetry, in the presence of an auxiliary of combustion to improve the complete oxidation reaction. These values were used to derive the stand ard molar enthalpies of formation of the crystalline compounds, at T = 298. 15 K, as -(612.9 +/- 1.5) kJ . mol(-1), -(614.7 +/- 1.3) kJ . mol(-1) and - (617.1 +/- 1.0) kJ . mol(-1), respectively, for the D-, L- and DL-valine. T he reliability of the results obtained is commented upon and compared with literature results for other alpha-amino acid isomers. (C) 2000 Academic Pr ess.