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| a cyclohexane ring shown in
a "Haworth projection," a format commonly used to depict carbohydrate
structures Note that this representation is not conformationally correct, but it does correctly depict the configuration, or absolute relationship of groups to each other. U = groups above the "plane" of the ring D = groups below the "plane" of the ring |
one possible chair
conformation of cyclohexane Note that three of the "U" groups actually do point upward and that three of the "D" groups actually do point downward. These six positions are called "axial" The remaining six groups are very roughly "in the plane" of the ring and are called "equatorial" |
when the ring is "flipped" from one chair conformation to the other, what was axial becomes equatorial and vice-versa. |
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| Here the axial positions
are labelled "A" (it should be lower-case, but the drawing program I used had its own agenda) and the equatorial positions are labelled "e" (why did it do the e the way I wanted when it wouldn't do the a that way?) |
methylcyclohexane in an
unfavored chair conformation. Note the van der Waals interaction
between the axial methyl group on C-1 and the axial hydrogens
on C-3 and C-5. Other H not shown for clarity |
methylcyclohexane in
the favored chair conformation. With the methyl group occupying an
equatorial position, the van der Waals strain is much lower. Only the H depicted in the drawing at left are shown here for clarity. |
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| cyclohexane in the boat
conformation the bond lengths and positions of the "flagpole hydrogens" (larger H) have been exaggerated for emphasis to show their unfavorable steric interaction (van der Waals strain) |
boat conformation viewed from a different angle, showing the unfavorable torsional strain due to the interactions of the "eclipsed" hydrogens (and the eclipsed upper carbons) on the lower four carbons | in the "skew boat" conformation, some relief has been achieved for both torsional and van der Waals strain |