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| Conformations of Cyclohexane |
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| In 1890, Sachse said that two puckered (non planar) models of cyclohexane are possible where the valence bonds of all the carbons were at tetrahedral angle to each other. They were found to be free from strain. |
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| One is the rigid chair form and the other the flexible boat form. |
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| There is no eclipsing and no angle strain in the chair form. By bending the lower portion of the chair form upwards or the back portion downwards, boat form can be got. When the chair form changes to the boat conformation two more conformations result. One is the boat form and the other the skew boat form (Skew meaning distorted). The different conformations of cyclohexane are given below: |
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| fig.12.7 - Conformation of cyclohexane |
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| Chair form of cyclohexane indicates two kinds of bonds. Each carbon atom has an equatorial and an axial bond. Thus there are 6 equatorial and 6 axial bonds in cyclohexane. Axial bonds are parallel to the three-fold axis of symmetry and the equatorial bonds are tetrahedral (109º 28') to the plane as shown below: |
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| fig.12.8 - Axial and equatorial bonds in cyclohexane |
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| When one conformer changes into another, potential energy changes are observed. The energy curves will give an idea about the stability of the conformers (more the energy, the less stable is the conformer) and also about the bond angles and kinds of bonds. |
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