The molecular structure of cis- and trans-bicyclo [4.2.0]-octane in the gas phase as studied by electron diffraction and molecular mechanics |
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| Authors: | A. Spelbos F.C. Mijlhoff W.H. Bakker R. Baben L. Van Den Enden |
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| Affiliation: | Gorlaeus Laboratories, University of Leiden, Department of Chemistry, P.O. Box 75, LeidenThe Netherlands;University of Antwerp (U.I.A.), Department of Chemistry, Universiteitsplein 1, Wilrijk 2610 Belgium |
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| Abstract: | The molecular structure of Cis- and trans-bicyclo[4.2.0]octane in the gas phase was studied. Molecular mechanics calculations applying Boyd's force Held were used for constraining differences between structural parameters during least squares analysis and for calculating vibrational amplitudes. The cyclohexane ring was found to have a distorted chair conformation, the ring in the cis isomer being flattened along the junction and more twisted in the other part. For the trans compound the reverse is true. The following structural parameters were obtained (ra-structure):cis: r(C-C)av. = 1.535 Å. Cyclohexane ring: average bond angle 112.9°; average torsional angle 48°. Cyclobutane ring: average bond angle 88.9°; puckering 157°. The dihedral angle between the bisecting planes of the C(2)-C(1)-C(6)-C(5) and C(8)-C(1)-C(6)-C(7) torsional angles, is 119° - the “connection angle” of the two rings.trans: r(C-C)av.= 1.532 Å. Cyclohexane ring: average bond angle 110.4° ; average torsional angle 57°. Cyclobutane ring: average bond angle 87.3°; puckering 145°. The “connection angle” is 180° (C2 symmetry).Comparison is made with structures of related compounds. |
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