Enthalpy of Formation and C−F Bond Enthalpy of Fluorofullerene C60F36

Abstract

The standard molar enthalpy of combustion of fluorofullerene C60F36 was determined by rotating-bomb calorimetry, ΔcH°m = −24692 ± 199 kJ·mol-1. Using this result and the standard molar enthalpy of sublimation, ΔsubH°m = 139 ± 8 kJ·mol-1, the values of the standard molar enthalpies of formation of C60F36 in the crystalline and gaseous states were found to be −5362 ± 201 kJ·mol-1and −5223 ± 201 kJ·mol-1, respectively. The enthalpy of reaction C60F36(g) = C60(g) + 36F(g) was calculated, ΔrH°m(298.15 K) = (10617 ± 202) kJ·mol-1, or 294.9 ± 5.6 kJ·mol-1 per one C−F bond. The comparison with the enthalpy of reaction C60F48 = C60(g) + 48F(g), ΔrH°m(298.15 K) = 287.5 ± 3.5 kJ·mol-1 per C−F bond leads to a preliminary conclusion that C−F bond enthalpy decreases with amount of F atoms attached to the fullerene cage.