Enthalpy of Formation and Strain of Norbornane from Thermochemical Measurements and from ab Initio Calculations

The standard molar enthalpy of formation Δ f H m °(cr) = −91.6 ± 1.2 kJ mol -1 at T = 298.15 K was determined by using combustion calorimetry for norbornane. The standard molar enthalpy of sublimation H m °(298.15 K) = 40.11 ± 0.43 kJ mol -1 of norbornane was obtained from the temperature dependence of the vapor pressure measured in a flow system. Its molar enthalpy of fusion H m ° = 4.35 ± 0.21 kJ mol -1 at T = 360.8 K was measured by DSC. Thermochemical investigations of norbornane available in the literature were collected and combined with own experimental results to obtain a reliable standard molar enthalpy of formation of norbornane Δ f H m °(g) = −53.6 ± 1.2 kJ mol -1 at T = 298.15 K in the gaseous state. Ab initio calculation of norbornane have been performed using the G3(MP2) basis set, and results from the bond separation method Δ f H m °(g) = −53.2 kJ mol -1 are in close agreement with experiment. A strain enthalpy of 71.8 kJ mol -1 of norbornane has been assessed using a group-additive procedure.