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Thermochemical Insights on the Conformational Energetics of Azepan and Azepan-1-ylacetonitrile
This paper is concerned
with computational and experimental thermochemical
studies of azepan and azepan-1-ylacetonitrile, molecules whose flexible
ring structure provides several conformational forms with low energy
barriers among them. The computational study describes the energetic
analysis of the six most stable conformers on the potential energy
surfaces and the determination of their gas-phase standard enthalpy
of formation at the reference temperature of 298.15 K. The same gas-phase
enthalpic parameters are also derived from the enthalpies of formation
in the liquid phase and the enthalpies of vaporization, at <i>T</i> = 298.15 K, determined experimentally using the combustion
calorimetry and the Calvet microcalorimetry techniques, respectively.
The experimental data reported in this work for the two titled compounds
together with other available in the literature for related molecules
enabled the establishment of an increments scheme, providing a reliable
approach on the prevision of gas-phase enthalpy of formation of cyclic/acyclic
hydrocarbons and amines. Complementary, natural bond orbital (NBO)
calculations were also performed, allowing an advance on the analysis
of the structural and reactivity behavior of these type of compounds