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

Abstract

The standard molar enthalpy of formation Δf 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 Δf 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 Δf 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.

Thermodynamic properties of caffeine: Reconciliation of available experimental data

“…An additional possibility to test the consistency of the selected data is the comparison of the experimental gaseous enthalpy of formation of caffeine with the value calculated using quantum chemical calculations. Such a test could be performed in the manner we suggested recently[15,16].…”

Thermal Decomposition of Norbornane (bicyclo[2.2.1]heptane) Dissolved in Benzene: Experimental Study and Mechanism Investigation

“…The apparatus (Figure 3) used for the experimental study of the thermal decomposition of norbornane (dissolved in benzene) has already been described in two papers about the pyrolysis of tricyclo[5.2.1.0 2,6 ]decane 14 and n-dodecane, 15 respectively Its main features are reminded and specificities linked to the dissolution of norbornane in benzene are discussed below.…”

“…9 The theoretical approach used for the calculation was validated by comparing calculated results with available experimental data. Several papers about the pyrolysis of tricyclo[5.2.1.0 2,6 ]decane, a tricyclic alkane, have been published. [10][11][12][13][14] Indeed this hydrocarbon is a component of synthetic fuels used in aeronautics.…”

“…The second objective of this paper is to describe the reactions involved in the mechanism of the pyrolysis of the norbornane -benzene binary mixture. These reactions include all the possible channels of unimolecular initiation of norbornane using a diradical approach as in the case of tricyclo[5.2.1.0 2,6 ]decane. 14 Cross-coupling reactions due to the presence of benzene in the feed of the reactor have been also reviewed although it will be shown later in this paper that benzene is not very reactive under the operating conditions of this study.…”

Determination of enthalpies (‘Heats’) of formation

“…Good combustion or reaction calorimetry is an exacting and time‐consuming technique that is destructive of extremely pure samples, which may have been won at great difficulty in their preparation. This being the case, it is likely that we will see more computed thermodynamic values in the chemical literature to come 18. Nevertheless, the laws of classical thermodynamics, now well into their second century, will continue to form a rigid framework within which any state change must take place, from physical phase changes to the complex pattern of chemical reactions that drive biological systems.…”