Enthalpy of formation and strain of norbornane from thermochemical measurements and from ab initio calculations

The standard molar enthalpy of formation Delta(f)H(m)degrees(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 Delta(cr)(g)H(m)degrees(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 Delta(cr)(l)H(m)degrees = 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 Delta(f)H(m)degrees(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 Delta(f)H(m)degrees(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.