Abstract
AbstractThe 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 C2 symmetric twist conformer of 1 is calculated to be more stable than the planar C2v geometry. Ring inversion of the envelope conformation of 2 takes place via C2 symmetric twist transition state, which is 34.0 kJ mol−1 higher than the envelope form. The C2 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
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