Cyclohexane Chair Flip

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Organic Chemistry | Conformation of Cyclic Alkanes - Part 3/3.

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Key Questions

  • A chair "flip": has nothing to do with flipping anything but rather cal lit a chair "conversion.":

    What you are doing is essential the same thing you would do with a beach lounge chair. You know the lounge chairs that flip both ways. Lie on a beach lounge chair and crank it so your head is up at the head end, your feet down toward the feet end. Now re work the chair so your head is now down and your feet up, breaking your legs if you are not flexible. So too is a ring "flip." You don't flip upside down you stay on top of the chair, only your head goes from up in the air to lower. A picture would really help here.

    What then happens is the axial up bonds convert to axial up equatorial, nothing flips upside down. Axial up bonds convert to equatorial up bonds. Equatorial or axial down bonds convert to the other, respectively.

    This is an attempt to be funny on a website that doesn't like funny answers, so to get the full experience go to my website


  • Answer:

    The chair conformation is most stable for cyclohexanes because it allows for ideal bond lengths and intramolecular interactions between carbon atoms within the ring.


    Within the natural world, cyclohexane molecules are constantly changing with flips and twists to boats and twist boats but it spends the majority of time in the standard chair conformation. Because of this initial experimental observation it can be reasoned that this is the most stable and "preferred" conformation.

    Digging a little deeper into why this is the case leads us back to a simpler methane molecule.

    Methane, #"CH"_4#, if you remember, has a carbon atom with 4 hydrogen atoms spaced exactly #109.5""^@# from each other to form the perfect tetrahedral molecule.

    Now, let's say we bound 6 methane molecules together into a ring but in a way that maintains as close to #109.5""^@# spacing as possible for each atom. This ideal structure that maintains the tetrahedral spacing for each methane is the chair conformation! (The actual bond angles in cyclohexane are #110.9""^@# but this is the closest it can get to #109.5""^@#)

  • Answer:



    All equatorial substituents become axial and vice versa.