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Conformational pathways of simple six‐membered rings
Author(s) -
Stortz Carlos A.
Publication year - 2010
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1689
Subject(s) - chemistry , pseudorotation , computational chemistry , basis set , ring flip , tetrahydropyran , cyclohexanone , ab initio , piperidine , chlorobenzene , cyclohexane conformation , potential energy , cyclohexane , electronic correlation , stereochemistry , density functional theory , ring (chemistry) , molecule , organic chemistry , atomic physics , hydrogen bond , physics , catalysis
The conformational equilibria of cyclohexane (as well as its fluoro‐, chloro‐, methyl‐, hydroxy‐, and t ‐butyl derivatives), cyclohexanone, piperidine, tetrahydropyran (and its 2‐hydroxy derivative) were studied by ab initio and DFT procedures. The transition states were calculated at HF/6‐31G, B3LYP/6‐31+G*, and B3LYP/6‐311+G** levels, whereas the intrinsic reaction coordinates (IRCs) were evaluated at the B3LYP/6‐31+G* level. The degree of puckering and energy data was nearly not basis set‐dependent (using B3LYP) in most of the cases. However, DFT methods gave better agreement with experimental data than HF methods, as expected from electron correlation inclusion. Fluorocyclohexane and 2‐hydroxytetrahydropyran showed the largest basis set‐energy dependence. It was found that the conversion from chair to skew is direct in some cases, whereas in others it goes through the pseudorotational (skew/boat) pathway. The case of t ‐butylcyclohexane, with a skew form as stable as one of the chairs, is especially interesting. In this compound, as well as in cyclohexanone and 2‐hydroxytetrahydropyran, large deviations from the known pseudorotation/inversion scheme are observed. Copyright © 2010 John Wiley & Sons, Ltd.