Title : Structure, charge delocalization and activation of C-C, C-H, C-X bonds in small cycloalkanes: Theoretical approach
Abstract:
The conversion of hydrocarbons involves reactions introducing carbocationic species having relatively stable structures or transition structures. A theoretical study in this direction was carried out on the activation of cycloalkanes (C3 to C5), by protonation of the C−C bond, followed by a geometry optimization calculation which revealed pentacoordinated systems (carbonium ions). These systems evolve towards bridged structures and ion-molecule interaction complexes. The analysis of the charge delocalization of these structures was carried out by the NBO theory. Carbodication systems were also optimized and followed by a correlation between the atomic charges and their chemical shifts 13C NMR. On the other hand, a theoretical study of the hydrotreatment process aimed at the elimination of sulfur, nitrogen and oxygen present in small heterocycles, such as thiirane, oxirane and aziridine was carried out. through the protonation of C-S, C-N and C-O bonds, followed by geometry optimization. The charge delocalization was calculated to estimate the participation of non-bonding heteroatom doublets in the formation of H-S, H-N and H-O bonds.
Keywords: conversion, cycloalkane, protonation, carbocations, hydrotreatment, small heterocycles, DFT/B3LYP, NBO analysis, 13C NMR.
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