The standard molar energies of combustion, Delta U-c degrees(m)(cr, 298.15 K), of alpha-D-glucoheptono-1,4-lactone (GH) and alpha,beta-glucooctanoic-1,4-lactone (GO) were obtained by micro-combustion calorimetry. The obtained values are -(2924.6 +/- 2.3) kJ . mol(-1) and -(3459.5 +/- 2.5) kJ . mol(-1), respectively. From combustion energies, the standard molar enthalpies of formation in crystalline phase, Delta H-f degrees(m) (cr, 298.15 K), for GH and GO were determined as -(1546.2 +/- 2.5) kJ . mol(-1) and -(1690.6 +/- 2.7) kJ . mol(-1), respectively. Also it was found that when the hydroxyl group number increases in the aldonolactones their standard molar enthalpies of formation increase too. (c) 2008 Elsevier Ltd. All rights reserved.