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Article Dans Une Revue Physical Chemistry Chemical Physics Année : 2023

Conformational preference analysis in C 2 H 6 using Orbital Forces and Non-Covalent Interactions; comparison with related systems

Trinidad Novoa

Résumé

Dynamic Orbital Forces (DOF) and Non-Covalent Interactions (NCIs) are used to analyze the attractive/repulsive interactions responsible of the conformational preference of ethane and some related compounds. In ethane, it is found that the stabilization of the staggered conformation with respect to the adiabatic eclipsed one arises from both attractive and repulsive interactions in CH 3 •••CH 3. Attractive ones are predominant in a ratio 2:1, with an important role of a sigma MO. On the contrary, the stabilization of the staggered conformation with respect to the vertical eclipsed one arises almost only from repulsive  interactions. Weak long-range H•••H repulsions also favour the staggered conformation. From the sum of DOFs, yielding intrinsic bond energies, the rotation barrier can be decomposed into a weakening of the CC bond (ca. 7 kcal/mol), moderated by a strengthening of C-H ones (ca. 4 kcal/mol). This evidences the decrease of hyperconjugation in the eclipsed conformation with respect to the staggered one. In the compounds CH 3-SiH 3 , SiH 3-SiH 3 , CH 3-CF 3 and CF 3-CF 3 , the conformational preference is predominantly or exclusively due to repulsive interactions, with respect as well to adiabatic as to vertical eclipsed structures.

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Chimie
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Dates et versions

hal-03969347 , version 1 (02-02-2023)

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Patrick Chaquin, Julia Contreras-Garcia, Trinidad Novoa. Conformational preference analysis in C 2 H 6 using Orbital Forces and Non-Covalent Interactions; comparison with related systems. Physical Chemistry Chemical Physics, 2023, 25, pp.4276-4283. ⟨10.1039/d2cp04913a⟩. ⟨hal-03969347⟩
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