Rotation of cycloalkanes

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Rotation of cycloalkanes

Postby rebecca_handler_1B » Mon Mar 13, 2017 2:16 pm

I understand that cyclopropane does not rotate and cyclobutane does, but I don't understand why that is. Can someone help me understand this?

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Re: Rotation of cycloalkanes

Postby Marco_Romo_1M » Mon Mar 13, 2017 2:46 pm

Looking at the 3-D model of cyclopropane, there is no conformation that could result in the 3 carbon molecules to not be in the same plane. For cyclobutane, two of the carbons can go up or down together, creating a non planar formation (butterfly) which is more stable because there is less torsional strain.

Shelby Slaughter 3D
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Re: Rotation of cycloalkanes

Postby Shelby Slaughter 3D » Mon Mar 13, 2017 3:17 pm

The Carbon atoms in cyclobutane, unlike cyclopropane, can rotate to stagger the hydrogen atoms and relieve torsional strain. Cyclopropane must be planar, and cyclobutane takes a butterfly confirmation because it is more stable this way than as planar.

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