The standard (pdegrees = 0.1 MPa) molar enthalpies of formation for liquid 2-chloropyrazine and crystalline 2,6-dichloropyrazine, 2,3-dichloroquinoxaline and 2,3,6,7-tetrachloroquinoxatine were derived from the standard molar enthalpies of combustion, in oxygen, to yield CO2(g), N-2(g), and HCl . 600H(2)O(l), at the temperature T = 298.15 K, measured by rotating-bomb combustion calorimetry. The standard molar enthalpies of vaporization or of sublimation, at T = 298.15 K, were measured by Calvet microcalorimetry.