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Ab initio molecular orbital study of conformational properties of cyclohexyne, cycloheptyne, and cyclooctyne
Author(s) -
Yavari Issa,
Nasiri Farough,
Djahaniani Hoorieh,
Jabbari Arash
Publication year - 2005
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.20833
Subject(s) - conformational isomerism , chemistry , ring flip , ab initio , racemization , twist , envelope (radar) , transition state , crystallography , computational chemistry , ab initio quantum chemistry methods , molecular orbital , ring (chemistry) , stereochemistry , molecule , geometry , telecommunications , radar , biochemistry , mathematics , organic chemistry , computer science , catalysis
The structures and relative energies for the basic conformations of cyclohexyne (1), cycloheptyne (2), and cyclooctyne (3) have been calculated by the HF/6‐31G*, MP2/6‐31G*, and B3LYP/6‐31G* methods. The C 2 symmetric twist conformer of 1 is calculated to be more stable than the planar C 2 v geometry. Ring inversion of the envelope conformation of 2 takes place via C 2 symmetric twist transition state, which is 34.0 kJ mol −1 higher than the envelope form. The C 2 symmetric chair conformation of 3 is calculated to be 11.7 kJ mol −1 more stable than the unsymmetrical twist‐boat (3‐TB) geometry. Interconversion of the chair conformation and 3‐TB takes place via an unsymmetrical transition state, which is 37.6 kJ mol −1 less stable than the chair form. Conformational racemization of the chiral 3‐TB takes place via the boat transition state. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2006