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Theoretical Study of Inversion and Topomerization Processes of Substituted Cyclohexanes: The Relevance of the Energy 3D Hypersurface
Author(s) -
FernándezAlonso María del Carmen,
Cañada Javier,
JiménezBarbero Jesús,
Cuevas Gabriel
Publication year - 2005
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200400495
Subject(s) - inversion (geology) , chemistry , heteroatom , conformational isomerism , computational chemistry , potential energy surface , transition state , dipole , point reflection , maxima and minima , potential energy , chemical physics , crystallography , ab initio , molecule , quantum mechanics , physics , mathematics , geometry , ring (chemistry) , organic chemistry , paleontology , mathematical analysis , structural basin , biology , catalysis
Although the potential energy surface of highly symmetric cyclohexane has been extensively reviewed, no attention has been paid to the study of the effect of substitution of a methylene group by a heteroatom. The substitution may cause changes in molecular symmetry as well as the dipole moment, and the unshared electron pairs associated with the heteroatom may also introduce changes in molecular reactivity. However, these phenomena are not yet completely understood. To address these issues, a rigorous description of the inversion–topomerization process of methylcyclohexane and a revision of the conformational potential energy of oxane and thiane are presented. Moreover, the usefulness of providing a three‐dimensional representation of these processes is discussed. In the case of methylcyclohexane, calculations show that three transition states are associated with inversion and four more with topomerization. In contrast, for oxane and thiane, only two transition states are involved with inversion and two with topomerization. Two fundamental conclusions can be drawn from this study. The first is that the inversion process occurs through elementary stages that we have denoted “conformational elemental stages”, which is an analogous term to that used for reaction mechanism description (minima–transition state–minima) where several elemental steps take place. The second conclusion is that two independent processes, inversion and topomerization, are connected by some common conformers. The inversion process controls the ring interchange, while topomerization allows exchange between skewed boats.