The standard molar energies of combustion, Delta(c)U degrees(m) (cr, 298.15 K) of 7-hydroxy-4-methylcoumarin, 7-ethoxy-4-methylcoumarin, and 6-methoxy-4-methylcoumarin were obtained by combustion calorimetry. The experimental values are (-4536.4 +/- 2.2), (-5888.0 +/- 3.2), and (-5267.3 +/- 2.3) kJ . mol(-1), respectively. From these values, the standard molar enthalpies of formation in the crystalline phase were calculated and found to be (-540.8 +/- 2.6), (-545.4 +/- 3.6), and (-488.0 +/- 2.7) kJ. mol(-1), respectively. (C) 2011 Elsevier Ltd. All rights reserved.