318M – Krische, Lecture 9: W - 09/17/08, Alkanes and Cycloalkanes•We began by taking a closer look at the chair conformation of cyclohexane. If one draws an axis through the center of the cyclohexane ring (perpendicular to the pseudo-plane of the ring), there are 6-hydrogens aligned with the axis (3 pointing up and 3 pointing down), termed “axial” hydrogens and 6-hydrogens roughly perpendicular to the axis (3 slightly tilted up and 3 slightly tilted down), termed the “equatorial” hydrogens. •There are two equivalent cyclohexane chair conformers that are able to interconvert. Upon chair interconversion, all axial hydrogens become equatorial hydrogens and all equatorial hydrogens become axial hydrogens. •The interconversion cyclohexane chair conformers precedes through the intermediacy higher energy conformers termed the “half-chair” conformation (10 Kcal/mol higher in energy), the “twist boat” conformation (5 Kcal/mol higher in energy), and the “boat” conformation (6.5 Kcal/mol higher in
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