cyclohexane_and_conformation

cyclohexane_and_conformation - Cyclohexane and the Chair...

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Cyclohexane and the Chair Structure: The chair structure of cyclohexane is considered to be the “perfect” conformation. The chair structure consists of a six-membered ring where every C-C bond exists in a staggered conformation. With no torsional strain (and no angle strain), cyclohexane is the most stable of all the small rings of the cycloalkanes. There are twelve possible positions on a chair structure. Six of the positions exist in vertical positions (known as “axial” positions) and the other six point out and away from the center of the ring, in an outwards direction (away from the equator of the ring, “equatorial” positions). Three of the axial positions point upward and the other three point down. The same is the case for the equatorial substituents – three face upwards and the other three face downwards (although these are definitely subtler!) Chair structures are considered to be conformationally mobile, meaning they are flexible (not as much so as a straight chain alkane but more so than any of the other smaller rings) and because of this flexibility, they “flip” from one possible chair to the other possible chair. You will notice that as the chair “flips”, the substituents in axial positions (such as A and D in the first chair) become equatorial in the second chair. Substituents in equatorial positions (such as B and C in the first chair) become axial. You should also take note that substituents that are pointing up (A, which is axial and C, which is equatorial) always stay facing up (A is up equatorial in the new chair and C is
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This note was uploaded on 12/22/2011 for the course CHEM 3053 taught by Professor Laurashirtcliff during the Fall '11 term at Oklahoma State.

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cyclohexane_and_conformation - Cyclohexane and the Chair...

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